Eel case method: 50 questions

A November night. A 50 cm eel kept in a 90 cm tank has come out of its pipe and keeps rubbing its body against the tank walls and bottom. Under a light, a dozen or so white spots like sprinkled salt are visible on its back and fins. Last week, new medaka (rice fish) were added to the same tank as live food. The thermometer reads 21°C and the heater setting has not been changed.

Which is the most appropriate first action?

1. Scrape the white spots off with your fingers or tweezers
2. Raise the water temperature 1°C per day to around 28°C, do a 1/4 water change daily, and consult a vet
3. Dilute a human disinfectant and add it to the tank
4. Add double the labeled dose of a fish medication you saw online to cure it faster

AnswerB. Raise the water temperature 1°C per day to around 28°C, do a 1/4 water change daily, and consult a vet

ExplanationWhite spots plus rubbing behavior are classic signs of white spot disease (ich): parasites attached to the skin. The parasites live shorter and leave the fish faster at higher temperatures, so the basic approach is to raise the water 1°C per day to around 28°C, avoiding sudden changes, and reduce the free-swimming parasites with daily 1/4 water changes. For medication, consult a vet who treats fish and follow the dose. Scraping off the spots tears the skin and invites secondary infection such as water mold. Human disinfectants damage the gills and can cause sudden death. Overdosing fish medication is highly toxic and dangerous for a fish like the eel, whose scales are vestigial. The new live food most likely brought the parasite in; see a vet within a few days, or the same day if it worsens.

IssuesLive food was added to the main tank without quarantine, introducing the parasite. The fall drop in water temperature lowered the fish's resistance and helped trigger the outbreak. The owner had the habit of observation to catch early signs of ich, but lacked knowledge of the treatment.

ImprovementObserve new fish or live food in a separate container for 2 weeks before adding them. Use a heater to keep the water at 22°C or above so it does not change sharply with the season. Find an animal hospital that treats fish in advance and post the contact details beside the tank. Always check the dose of any medication and never increase it on your own judgment.

6 a.m. on a July morning. On waking, the owner finds the eel in the 60 cm tank with its mouth at the surface, gasping. Normally it stays in its pipe and is never seen during the day. Last night, back from a trip, the owner fed it a large amount for the first time in a while, and uneaten food has sunk to the bottom. The filter is running, but the flow from the outlet seems weak. The water is slightly cloudy and white.

Which is the most appropriate first action?

1. Turn aeration to maximum, remove the leftover food, do a 1/3 water change, and test the water with a test kit
2. Assume it is begging for food since it is at the surface and feed it more
3. Drain all the water and replace it with fresh tap water
4. Assume it is the heat and drop ice straight into the tank to cool it

AnswerA. Turn aeration to maximum, remove the leftover food, do a 1/3 water change, and test the water with a test kit

ExplanationGasping at the surface (piping) is a sign of oxygen shortage or ammonia/nitrite poisoning. Rotting leftover food and a clogged filter have likely caused a sudden drop in water quality. First turn aeration to maximum to supply oxygen, remove the leftover food, do a 1/3 water change to dilute the toxins, and confirm the cause with a test kit. If it does not improve, see a vet the same day. Adding more food worsens the water further. A full water change loses the filter bacteria, destabilizes the water, and the chlorine in tap water damages the gills. Dropping in ice causes a sudden temperature change and shock.

IssuesHeavy feeding after returning home and leaving the leftovers in the tank was the trigger. The owner had noticed the reduced filter flow but kept putting off cleaning. There was no backup aeration during summer, when high water temperatures reduce dissolved oxygen.

ImprovementFeed only what is eaten within 5 minutes and remove leftovers every time. Check the filter flow weekly and rinse the filter in tank water once a month. Run an air pump permanently in summer and keep a battery-powered pump for power outages. Keep ammonia and nitrite test kits on hand and make it a habit to test before and after water changes.

A January night. A 60 cm eel kept in an unheated 90 cm tank is lying motionless on the bottom. Pinpoint red bleeding is spreading over its belly and lower jaw, and it has not eaten for a week. The water is 17°C; the heater was removed last month to save electricity. A test kit shows no ammonia or nitrite.

Which is the most appropriate first action?

1. Do nothing until spring, since not eating in winter is normal
2. Quickly raise the temperature to 26°C all at once with a heater
3. Put the heater back, raise the water 1–2°C per day to 22°C or above, and contact a vet who treats fish the same day
4. Rub salt into the red areas to disinfect them

AnswerC. Put the heater back, raise the water 1–2°C per day to 22°C or above, and contact a vet who treats fish the same day

ExplanationPinpoint red hemorrhages spreading over the belly and lower jaw are typical of a bacterial infection (red spot disease) that occurs in cold-water periods. It develops easily below 20°C, and the basis of treatment is returning the water to 22°C or above, but raising it suddenly stresses the fish, so increase by 1–2°C per day. Bacterial infections need antibiotics, so contact a vet who treats fish the same day. Left untreated, the infection becomes systemic and kills the fish. Raising the temperature all at once causes temperature shock. Rubbing in salt destroys the skin and makes it worse.

IssuesThe heater was removed to save electricity, keeping the eel below its proper range (22–28°C) for a long period. The loss of appetite was dismissed as winter and only observed for a week. The response was slow even after the red spots appeared.

ImprovementIn winter, either keep the water at 22°C or above with a heater, or, if managing a dormancy period, hold it stable around 15°C; avoid a halfway 17°C. If the eel refuses food for 3 days in a row, check the water temperature and the skin. Learn that bleeding on the belly or at the base of the fins is a sign of bacterial infection and consult a vet the same day it appears.

An August evening. Two eels are kept in a 120 cm tank. One has a red, swollen area around the vent, a bloated belly, and redness at the base of the fins. It has not eaten for several days. The water has risen to 31°C; a cooling fan is running but is not very effective. The other eel is swimming around energetically.

Which is the most appropriate first action?

1. Give both eels a medicated bath, since the healthy one may have the same disease
2. Press on the belly to squeeze out the contents
3. Isolate the sick eel in a separate container, lower and stabilize the temperature, and contact a vet the same day
4. Force food into its mouth to build up its strength since it is not eating

AnswerC. Isolate the sick eel in a separate container, lower and stabilize the temperature, and contact a vet the same day

ExplanationA swollen vent, bloated belly, and bleeding at the base of the fins during a hot-water period strongly suggest a bacterial infection (such as Edwardsiella). Infection spreads through the water, so first isolate the individual carrying the pathogen in a separate container. Gradually lower the water to 28°C or below and stabilize it, withhold food to reduce stress, and contact a vet who treats fish the same day for diagnosis and treatment. Bathing both fish is medicating without a diagnosis and burdens the healthy one. Pressing the belly damages the internal organs. Force-feeding is dangerous for a weakened fish.

IssuesA cooling fan alone was insufficient against midsummer heat. With two eels, the organic load was high for the water volume, and high temperature combined with poor water quality let bacteria multiply. There was no spare container, heater, or air pump for isolation.

ImprovementInstall an aquarium chiller in summer and keep the water at 28°C or below. Keep a 30–45 cm isolation container, air pump, and heater on hand. With multiple eels, do water changes twice a week and always remove leftover food. Learn that a bloated belly or a red vent is a sign to consult a vet the same day.

A March night. The eel is poking its head out of its pipe, and there is something white and cotton-like on its snout. The owner remembers it scraped its snout when it was netted during a move last week. It does not approach food and stays motionless. The water is 19°C; the heater broke and has been off for 2 days.

Which is the most appropriate first action?

1. Pull the cotton-like growth off with tweezers
2. Replace the heater, bring the water back above 20°C, get the water quality as good as possible, and consult a vet the same day
3. Increase the amount of food, assuming it will come off with eating since it is on the snout
4. Add water from the garden pond to make the tank more natural

AnswerB. Replace the heater, bring the water back above 20°C, get the water quality as good as possible, and consult a vet the same day

ExplanationWhite cotton-like material on a wound is water mold (saprolegniasis), which grows on damaged tissue. It develops easily below 20°C; here the scrape from the net and the low temperature combined to cause it. First replace the broken heater to bring the water back above 20°C, do a water change to get the water as clean as possible to suppress the mold, and consult a vet who treats fish the same day. Left alone, the mold will cover the mouth and the fish will be unable to eat. Pulling it off with tweezers enlarges the wound and worsens it. More food degrades the water. Pond water brings in pathogens and parasites.

IssuesChasing the eel with a net and injuring its snout was the start. The broken heater was noticed but left for 2 days, and the low temperature lowered the fish's immunity. There was no spare heater, so the failure could not be addressed right away.

ImprovementMove the eel by scooping it up with water in a container, not a net, so the skin is not damaged. Keep one spare heater and check the thermometer every morning. After an injury, keep the water as clean as possible and check the skin daily for several days; if a cotton-like growth appears, consult a vet the same day.

A May night. A 55 cm eel is floating at an angle near the surface and bobs back up whenever it tries to dive. Its body is thin, but only the belly is swollen. The eel was received six months ago from a friend who likes fishing and is of wild origin; since then it has been fed shrimp and loaches caught in a river as live food.

Which is the most appropriate first action?

1. Assume it swallowed too much air and puncture the swim bladder with a needle to release it
2. Mix a pet digestive supplement into its food
3. Assume temporary indigestion, stop feeding, and watch for 2 weeks
4. Lower the water level to prevent exhaustion, take photos, and consult a vet who treats fish the same day

AnswerD. Lower the water level to prevent exhaustion, take photos, and consult a vet who treats fish the same day

ExplanationA thin body with only the belly swollen, floating and unable to dive, suggests swim bladder nematode infestation, which enters through wild-origin fish or wild-caught live food, or an internal disease. It cannot be diagnosed at home, so lower the water level so the fish does not exhaust itself trying to dive, photograph the symptoms, and consult a vet who treats fish the same day. Deworming requires a veterinary prescription. Puncturing the swim bladder with a needle causes fatal internal damage. Giving human or dog/cat medication is dangerous because the dose is unknown. Waiting 2 weeks lets the fish weaken past the point of help.

IssuesA wild-origin individual was taken in without examination, and wild-caught live food continued to be fed, bringing in parasites. The contradictory change in body shape (thin yet bloated) was noticed late. The owner also did not know that catching wild eels is regulated.

ImprovementHave a wild-origin eel examined, including a fecal test, at a vet who treats fish before taking it in. Avoid wild-caught live food; use commercial frozen food or formulated feed. Photograph the body from the side once a month for comparison. Know that catching eels is restricted by prefectural government rules and confirm that the source was legal.

A night in early December. A 65 cm eel in its third year of keeping has not eaten for 3 days. There are no wounds or white spots on the skin, and the gill covers move calmly. It stays still in its pipe but swims slowly when the light is turned off. The water is 19–20°C; the heater is set to 23°C but cannot keep up with the daytime cold. Water tests show nothing abnormal.

Which is the most appropriate first action?

1. Upgrade to a higher-wattage heater to stabilize the water at 22°C or above, reduce feeding, and observe
2. Rush it to an emergency (after-hours) animal hospital right now, since not eating means illness
3. Leave plenty of frozen bloodworms in every night to stimulate its appetite
4. Assume stress, remove the pipe, and make the tank brighter

AnswerA. Upgrade to a higher-wattage heater to stabilize the water at 22°C or above, reduce feeding, and observe

ExplanationWith a normal skin, normal breathing, and normal water quality, a drop in appetite around 20°C is a normal response to low temperature. The cause is an underpowered heater, so replace it with one matched to the tank size and stabilize the water at 22°C or above; the appetite will return. Digestion slows in the cold, so reduce feeding, and see a vet if it still does not eat for a week after the temperature is restored. Rushing to an emergency hospital with no symptoms causes more stress from the move. Food left uneaten rots and degrades the water. Removing the hideout and brightening the tank is severely stressful for a nocturnal eel.

IssuesThe heater's wattage did not match the tank and room conditions, so it could not hold the set temperature in winter. The owner did follow the procedure of ruling out water temperature, water quality, and the skin in order, but did not check the heater's performance.

ImprovementChoose a heater sized for the water volume and the room, and confirm before winter that it can hold the set temperature. Record the water temperature morning and evening and act if it swings by 2°C or more. When the eel stops eating, check four things: water temperature, water quality, skin, and breathing; see a vet if anything is abnormal, and start with adjusting the environment if not.

Late on an October night. An 80 cm eel in its eighth year of keeping has turned silvery white on its underside and its eyes look enlarged. It has barely eaten for the past month, and the owner was woken by the sound of it swimming violently around the tank and ramming the lid. There are no wounds on the skin and the water quality is normal. There is a river nearby, and the family suggests it would be better to release it to go back to the sea.

Which is the most appropriate first action?

1. Release it into the nearby river to return it to nature
2. Treat it as sick and give it a medicated bath to restore its appetite
3. Recheck the lid weights and gaps, dim the lights to prevent escape, continue keeping it, and see a vet if anything abnormal appears
4. Lower the water level drastically so it cannot move and thrash

AnswerC. Recheck the lid weights and gaps, dim the lights to prevent escape, continue keeping it, and see a vet if anything abnormal appears

ExplanationThe change to silvery white, enlarged eyes, loss of appetite, and violent nighttime swimming are the normal physiological change called silvering, in which the mature eel tries to migrate to the sea; it is not a disease. Escapes are most common at this stage, so recheck the lid weights and gaps, dim the lights to calm it, and continue keeping it. The appetite may not return, but see a vet if the skin looks abnormal or the fish weakens. Releasing a captive fish spreads pathogens, disrupts the genetics of wild populations, and violates local fishery regulations, so never do it. A medicated bath for a fish that is not sick is a burden. A drastic drop in water level degrades water quality and causes oxygen shortage.

IssuesThe owner did not know that a long-kept eel would reach maturity and mistook silvering for illness. The family did not share the understanding that the eel is an endangered species that must never be released, as shown by the suggestion to release it. The escape precautions did not anticipate the violence of the silvering stage.

ImprovementShare with the family that eels are long-lived, silver on maturing, and thrash about, and decide in advance that release is never an option. Add weights to the lid and seal every gap completely with netting. If continuing to keep it becomes difficult, research in advance who could take it in, such as the shop of purchase, a vet who treats fish, or an aquarium.

A June night. A 45 cm eel has its head out at the entrance of its pipe and is breathing fast. On closer inspection, the right gill cover moves constantly, but the left barely opens. It keeps moving toward the strong current from the filter outlet. Water temperature is 26°C. The owner skipped cleaning the filter 2 weeks ago, and feces have accumulated on the bottom. A test shows high nitrite.

Which is the most appropriate first action?

1. Open the gill cover with your finger and wash the inside
2. Turn aeration to maximum, lower the nitrite with a 1/3 water change and bottom cleaning, and see a vet the same day if there is no improvement
3. Assume it is a dominant-gill issue since only one side is affected and leave it
4. Raise the water to 32°C all at once to kill bacteria

AnswerB. Turn aeration to maximum, lower the nitrite with a 1/3 water change and bottom cleaning, and see a vet the same day if there is no improvement

ExplanationFast breathing, one gill cover not moving, and gathering in the current are typical of gill damage (gill disease) caused by nitrite or ammonia. First turn aeration to maximum to supply oxygen, then lower the nitrite with a 1/3 water change and bottom cleaning. Gill damage progresses quickly, so if there is no improvement within a few hours, go to a vet who treats fish the same day. Forcing the gill cover open tears the delicate gill tissue and causes bleeding. Left alone, the fish dies of respiratory failure. 32°C exceeds the proper range and reduces oxygen, killing the fish.

IssuesFilter cleaning was neglected, and accumulated feces raised the nitrite. The owner did not anticipate that organic matter breaks down faster in summer's high temperatures and water quality can crash suddenly. A test kit was on hand but not used regularly.

ImprovementSiphon feces from the bottom daily and rinse the filter in tank water once a month. Test and record nitrite and ammonia weekly, and do an immediate water change if either is not zero. Make it a habit to compare the left and right gill covers during each evening feeding.

An April afternoon. Because the water was dirty, the owner drained all the water from the 90 cm tank and refilled it at once with dechlorinated fresh water. Ten minutes after the eel was returned, it writhed violently, then fell on its side on the bottom with only its gill covers moving rapidly. The new water was at tap temperature, 5°C lower than the original tank, and the pH may also differ from the old water.

Which is the most appropriate first action?

1. Stand the fish upright by hand and make it swim
2. Restore the original temperature with the heater, turn aeration to maximum, turn off the lights to let it rest, and see a vet immediately if it does not recover
3. Add several kinds of commercial additives said to help with shock all at once
4. Replace the water with new water again and start over

AnswerB. Restore the original temperature with the heater, turn aeration to maximum, turn off the lights to let it rest, and see a vet immediately if it does not recover

ExplanationA full water change that drops the temperature by 5°C and shifts the pH causes temperature and pH shock, which makes the fish fall on its side. What can be done now is to restore the original temperature with the heater, turn aeration to maximum to supply oxygen, and turn off the lights to reduce stimulation. If it stays on its side for more than 30 minutes or the gill movement weakens, see a vet immediately. Standing it up by hand only strips the mucus and adds stress. Dumping in multiple additives disturbs the water further. Another full water change is a double shock and can be fatal.

IssuesThe owner chose a full water change, the most dangerous method, and did not match temperature or pH. They did not know the basics: change 1/3 at a time, with a temperature difference within 2°C. Delayed maintenance let the water get dirty enough to force a full change.

ImprovementMake a weekly 1/3 water change the rule, match the temperature of the new water, and add it slowly by drip. Measure pH and temperature before and after changes. Make bottom cleaning and partial changes a habit before the dirt becomes noticeable and avoid full changes. Remember the threshold for seeing a vet for shock (on its side for more than 30 minutes).

A September night. The owner notices that the left eye of a 50 cm eel is cloudy white and bulging slightly. The right eye is normal and the swimming looks normal. Three days ago the driftwood layout was changed, and the owner saw the eel thrash after pushing its head into a gap. Water temperature is 27°C and water quality is normal. It is eating.

Which is the most appropriate first action?

1. Do not touch the eye or apply eye drops; remove the driftwood, keep the water as clean as possible, and see a vet within a few days
2. Apply human eye drops to the eye inside the tank
3. Leave it until it heals, since it is eating even with one eye
4. Add a large amount of salt for a strong salt bath to clear the cloudiness

AnswerA. Do not touch the eye or apply eye drops; remove the driftwood, keep the water as clean as possible, and see a vet within a few days

ExplanationClouding and bulging of one eye suggests trauma from hitting the driftwood or a bacterial infection following it. A fish's eye cannot be treated directly underwater, so remove the driftwood that caused it to prevent another collision, do a water change to keep the water as clean as possible to prevent infection, and have a vet who treats fish examine it within a few days. If it spreads to both eyes, the fish stops eating, or the swimming becomes abnormal, see a vet the same day. Human eye drops have no effect underwater and the chemicals foul the water. Left alone, the fish may lose the eye or develop a systemic infection. Strong salt water damages the skin of the eel, whose scales are vestigial, and is dangerous.

IssuesThe driftwood layout created narrow gaps without considering the eel's habit of pushing its head into openings. The gaps were not checked when the thrashing was seen. The owner did not know how to handle an eye problem and could have chosen self-treatment.

ImprovementUse PVC or ceramic pipes with an inner diameter at least twice the body as hideouts and avoid driftwood that creates narrow gaps. After changing the layout, observe nighttime behavior for several days. Make it a habit not to treat eye, mouth, or gill problems at home, but to photograph them and consult a vet who treats fish.

A February night. The eel's whole body looks cloudy white, and mucus is peeling off in threads and drifting in the water. It rubs itself against the pipe and does not eat. The water is stable at 22°C. Last week, a commercial algae inhibitor was added to control algae, and a little tap water was topped up without dechlorinating it.

Which is the most appropriate first action?

1. Rub off the peeling mucus by hand to clean it
2. Add more algae inhibitor to clear the water
3. Stop using additives, do a 1/3 water change with dechlorinated water for 2 days in a row, and see a vet the same day if there is no improvement
4. Assume it is dirt on the skin, take the fish out, and wash it under tap water

AnswerC. Stop using additives, do a 1/3 water change with dechlorinated water for 2 days in a row, and see a vet the same day if there is no improvement

ExplanationMucus turning cloudy white and peeling is a sign of chemical irritation from medications or chlorine, or of skin inflammation caused by parasites. Here the algae inhibitor and chlorinated water are suspected, so stop using additives and do a 1/3 water change with dechlorinated water for 2 days in a row to dilute the irritant. The mucus is the membrane that protects the body from pathogens, so if there is no improvement, go to a vet who treats fish the same day. Rubbing the mucus by hand strips the protective layer and leads to infection. More inhibitor increases the irritation. Washing the fish under tap water is the worst option: the chlorine damages the gills and skin.

IssuesThe owner did not know that the eel has vestigial scales, relies on mucus for protection, and is sensitive to chemicals and chlorine. The algae inhibitor was used without checking its effect on fish, and dechlorination was skipped. Making several changes at once made the cause hard to identify.

ImprovementRemove algae by hand and do not use additives. Always dechlorinate top-up water. Change one thing in the tank at a time and observe for several days before changing the next. Remember cloudy or peeling mucus as a sign to see a vet.

7 a.m. on an August morning. The tank lid has slipped, and the eel is lying limp on the floor 2 m from the tank. Its skin is still slightly moist but covered in dust and hair, and its mouth is moving faintly. No one knows how many hours it has been on the floor. The family says it is dead and is about to put it in a bag.

Which is the most appropriate first action?

1. Decide it is dead, bag it, and dispose of it
2. Rinse the dust off under tap water, then return it to the tank
3. Return it to a container of tank water with wet hands, turn aeration to maximum to get water through the gills, and observe to decide whether a vet is needed
4. Dry the body thoroughly with a towel, then return it to the tank

AnswerC. Return it to a container of tank water with wet hands, turn aeration to maximum to get water through the gills, and observe to decide whether a vet is needed

ExplanationEels can breathe through their skin and survive a long time in air as long as the skin stays moist. The mouth is moving, so it is alive; do not give up. Pick it up gently with wet hands, return it to a container of tank water, turn aeration to maximum, and gently move it with its head forward so water passes through the gills. Rinse off the dust with tank water. If it swims on its own within 30 minutes, keep observing; if it stays on its side or keeps spinning, see a vet the same day. Assuming death and disposing of it is premature. Tap water's chlorine further harms the damaged gills. Wiping with a towel strips the mucus and damages the skin.

IssuesThe lid had no weights and could not prevent escape through the gap. Despite the eel being nocturnal and most active at night, the lid was not checked at night. The family did not know the eel can survive by skin breathing and nearly gave up on a life that could be saved.

ImprovementWeight the lid and seal gaps around plumbing and cords with netting. Keep the water level at least 5 cm below the rim. Make it a habit to check the lid position before bed. Tell the whole family that an eel on the floor may still be alive and should be returned to tank water with wet hands.

A May afternoon. The owner tried to net the eel to clean the tank, but it thrashed, struck its body against the rim of the net, and was caught only after being chased repeatedly. After it was moved to a separate container, a 3 cm patch on its flank has lost its mucus, turned red, and is slightly bloody. The eel is moving restlessly around the bottom of the container.

Which is the most appropriate first action?

1. Apply a human disinfectant to the wound, then return it to the tank
2. Keep it in the water, observe the wound, keep the water as clean as possible, and consult a vet the same day if a cotton-like growth or swelling appears
3. Let it rest on a dry towel until the wound heals
4. Rub salt directly into the wound to sterilize it

AnswerB. Keep it in the water, observe the wound, keep the water as clean as possible, and consult a vet the same day if a cotton-like growth or swelling appears

ExplanationA shallow abrasion where the mucus has come off usually heals as the mucus regenerates, provided the fish stays in the water and the water is kept as clean as possible. Do not touch the wound; after cleaning, return the fish to clean water and check the wound daily for several days. If a white cotton-like growth (water mold) appears, or the swelling or redness spreads, a bacterial infection is suspected, so consult a vet the same day. Human disinfectants destroy the mucous membrane and leach into the water, damaging the gills. On a dry towel the fish cannot breathe through its skin and dries out and dies. Rubbing in salt enlarges the wound and is especially harsh on a scaleless eel.

IssuesChasing it with a net is the most stressful way to catch a fish protected by mucus. No transfer container was prepared and no cleaning procedure had been decided. Forcing the capture of a thrashing eel added more injuries.

ImprovementMove the eel by scooping up its pipe with water in a container, not with a net. Lifting the hideout pipe while it is inside causes less thrashing. Clean without removing the fish, using bottom cleaning and partial water changes. After an injury, decide on several days of observation and the signs that call for a vet (cotton-like growth, swelling).

A November night. The eel has pushed its head into a small hole at the end of its pipe and is stuck at the thick part of its body. It is thrashing its tail violently, and the skin where it touches the edge of the hole is starting to turn white. The pipe was put in 2 years ago when the eel was a juvenile, and the body has grown thicker since.

Which is the most appropriate first action?

1. Grab the tail and pull as hard as you can
2. Lift the whole pipe while keeping it underwater, widen the hole or break the pipe, free the eel gently, and check for injuries
3. Leave it to free itself and wait until morning
4. Take the pipe out of the water and let it dry to make it slippery enough to pull out

AnswerB. Lift the whole pipe while keeping it underwater, widen the hole or break the pipe, free the eel gently, and check for injuries

ExplanationPulling a stuck fish by the tail tears the skin and damages the spine and internal organs. Lift the whole pipe while keeping it submerged, then widen the hole or break the pipe underwater and free the fish without applying force to it. Afterward check for skin damage and a bent body; if the body stays bent or it cannot swim, see a vet immediately. Leaving it thrashing until morning risks death from suffocation or self-injury. Out of the water, the mucus is lost, so it is less slippery, not more, and the fish, now relying on skin breathing alone, dries out and is in even greater danger.

IssuesThe pipe added when the eel was a juvenile was never reviewed after it grew, leaving a fixture with a hole too small for its body. The eel's habit of pushing its head into holes was not considered. The owner did not know how to handle a stuck eel and could have chosen the dangerous option of pulling.

ImprovementHideout openings should have an inner diameter at least twice the body, and the hideout should be replaced every six months to match growth. Do not place fixtures closed at one end or decorations with narrow holes. Agree as a family that a stuck eel is freed by removing the fixture underwater, and keep a tool that can break the pipe if needed.

A March afternoon. While carrying the eel in a bucket for a house move, the owner slipped on the stairs and dropped the bucket. The eel was slammed onto the floor from a height of 1 m and lies motionless, its body bent in a V shape. A little blood is coming from its mouth. The water has spilled and the floor is dry.

Which is the most appropriate first action?

1. Return it to a container of tank water with wet hands, check the bleeding and body deformity, and see a vet immediately if it stays on its side or keeps spinning
2. Straighten the body by hand to reset the spine
3. Leave it on the floor without moving it until the shock passes
4. Pack cotton into its mouth to stop the bleeding

AnswerA. Return it to a container of tank water with wet hands, check the bleeding and body deformity, and see a vet immediately if it stays on its side or keeps spinning

ExplanationWhen a fish lies motionless with its body bent in a V after a fall from height, spinal or internal injury is suspected. First lift it with wet hands and return it to a container of tank water to secure skin and gill breathing. Check the site of bleeding and the body deformity; if it stays on its side, spins, or remains bent, spinal injury is likely, so see a vet immediately. Bleeding from the mouth can also be a sign of internal injury, so report that too. Straightening the spine by hand spreads the damage. Left on a dry floor, it dies of drying out. Cotton in the mouth stops it from breathing.

IssuesThe eel was carried up stairs in a bucket without a lid. The choice of transport container and the safety of the route were not properly considered. No container that could be held with both hands or a lidded bag was prepared, and a fall or drop was not anticipated.

ImprovementFor transport, double-bag the eel in thick bags with tank water and air, place it in a foam box, and hold it with both hands. On stairs, have one person lead and use the handrail. Use a lidded container even for short distances. Remember the signs after a fall that call for a vet (on its side, spinning, bleeding from the mouth or gills).

A July night. A 70 cm eel that is used to being hand-fed has bitten down on the owner's finger along with the food. Its fine teeth are dug into the finger, and the eel is twisting its body and will not let go. The fingertip is bleeding and the hand is still in the tank. The owner tried to pull the hand out in surprise but cannot because of the pain.

Which is the most appropriate first action?

1. Pull the hand out as hard as you can
2. Keep the hand still in the water; if it does not let go, press lightly behind the gill covers to make it open its mouth
3. Grab the eel's body with a dry towel and pull it off
4. Slam the eel's head against the tank wall to make it let go

AnswerB. Keep the hand still in the water; if it does not let go, press lightly behind the gill covers to make it open its mouth

ExplanationAn eel's teeth are fine and angled backward, so pulling tears the skin and deepens the wound. If you keep the hand still in the water, the eel usually realizes it is not food and lets go on its own. If it does not, pressing lightly behind the gill covers makes it open its mouth. Once free, do not chase the fish; turn off the lights and let it rest. Wash the hand with soap and running water and disinfect it; if swelling, heat, or red streaks appear, a bacterial infection is possible, so see a doctor the same day. Gripping it with a dry towel strips the mucus and injures the fish. Hitting the head damages the brain and spine.

IssuesThe habit of feeding directly by hand led to an accident where the eel could not tell finger from food. The owner did not consider that this nocturnal fish finds food by smell more than sight. Not knowing how to respond to a bite, the owner reflexively tried to pull away.

ImprovementFeed with long tweezers or a feeding stick and keep fingers out of the water. Do not put hands that smell of food into the tank. Share the procedure as a family: if bitten, hold still in the water, then press behind the gill covers. Remember the signs on the hand that call for a doctor (swelling, heat, red streaks).

A January night. With the heater guard off, the eel was resting with its body wrapped around the heater. When the owner noticed and shooed it away, a band of its trunk had turned white and the mucus had come off. The eel keeps twisting as if bothered by the area. The water is a normal 23°C. The guard had been left off since last week's cleaning.

Which is the most appropriate first action?

1. Apply ice water to the burn to cool it
2. Put the guard back on the heater, keep the water as clean as possible, check the burn daily, and consult a vet the same day if a cotton-like growth or ulcer appears
3. Apply human burn ointment to the area
4. Lower the water level to expose the burn to air and dry it

AnswerB. Put the guard back on the heater, keep the water as clean as possible, check the burn daily, and consult a vet the same day if a cotton-like growth or ulcer appears

ExplanationA band of skin turned white from contact with the heater is heat damage, like a low-temperature burn. A fish in water cannot have the area cooled or have ointment applied, so put the guard back on the heater to prevent a recurrence, do a water change to keep the water as clean as possible to prevent infection, and check the area daily. If a white cotton-like growth (water mold), ulceration, or loss of appetite appears, consult a vet the same day. Local cooling with ice water causes temperature shock. Human ointment washes off underwater, fouls the water, and damages the gills. Exposing the area to air dries it and makes it worse.

IssuesThe heater guard was not put back after cleaning. The owner did not know that eels like to wrap themselves around warm objects and that an unguarded heater causes burns. There was no procedure for checking equipment after cleaning.

ImprovementAlways use the heater with its guard, and make a post-cleaning checklist in the order: heater guard, lid, netting. Place the heater away from the pipe. Photograph the burn daily to compare changes and decide the signs that call for a vet.

A June night. The eel got caught in a gap in the lid, its skin tore, and it bled while being freed. The owner was working bare-handed when a splash of bloody water got into one eye; within minutes the eye began to burn and turned red. There is also a small cut on a finger, which got blood on it. The eel has been returned to the tank and has calmed down.

Which is the most appropriate first action?

1. Rub the eye to get the foreign matter out and put up with it for a while
2. Immediately flush the eye with plenty of running water for at least 10 minutes, and see an eye doctor if the pain or redness persists
3. Do nothing, since eel blood is harmless
4. Use whatever eye drops are on hand and wait

AnswerB. Immediately flush the eye with plenty of running water for at least 10 minutes, and see an eye doctor if the pain or redness persists

ExplanationEel blood contains a protein toxin (ichthyotoxin in the serum) that causes severe inflammation if it gets into the eyes, mouth, or a wound. It is destroyed by heat, but raw blood is dangerous. If it gets into the eye, flush immediately with running water for at least 10 minutes; if pain or redness persists or vision is blurred, see an eye doctor and tell them eel blood got in. Wash the finger wound thoroughly with soap and running water too. Rubbing the eye damages the cornea and spreads the toxin. Assuming it is harmless and leaving it lets conjunctivitis or keratitis worsen. Commercial eye drops are no substitute for flushing.

IssuesThe owner did not know that eel blood is toxic and handled a bleeding fish bare-handed. Gloves were not worn despite a cut on the hand. The lid-gap accident itself arose from a failure to inspect the lid.

ImprovementWear gloves and protective glasses when handling a bleeding fish. If there is a cut on your hand, avoid tank work or always wear gloves. Make sure the family knows eel blood must not get into the eyes, mouth, or wounds. Seal lid gaps with netting to prevent entrapment.

A September night. In a 120 cm tank shared with a bichir, about 5 cm of the eel's tail tip has been bitten off; the stump is bleeding and torn skin is fluttering. The eel has retreated into its pipe and will not come out. The bichir apparently mistook the eel's tail for food at feeding time. Water temperature is 27°C.

Which is the most appropriate first action?

1. Isolate the eel in a separate tank, keep the water as clean as possible, and consult a vet the same day if the bleeding continues or a cotton-like growth appears
2. Trim the torn skin neatly with scissors
3. Take the fish out and press gauze on the wound to stop the bleeding
4. Keep them together and see how it goes

AnswerA. Isolate the eel in a separate tank, keep the water as clean as possible, and consult a vet the same day if the bleeding continues or a cotton-like growth appears

ExplanationEven a large tail injury can regenerate if the water quality is good, but it will be bitten again if the fish stay together. First isolate the eel in a separate tank and do a water change to keep the water as clean as possible to prevent secondary infection. Bleeding in fish is controlled by water management without removing the fish; if it continues for several hours, a cotton-like growth or swelling appears, or the eel stops eating, consult a vet who treats fish the same day. Cutting the skin with scissors enlarges the wound. Gauze out of the water does not stop bleeding, strips the mucus, and blocks skin breathing. Kept together, the wound will not heal and the eel may be bitten to death.

IssuesThe basic rule that keeping an eel with predatory fish or fish that can fit it in their mouth is dangerous was ignored. A bite from mistaking it for food at feeding time was not anticipated. No isolation tank or equipment had been prepared.

ImprovementKeep eels alone as a rule; if sharing a tank, limit it to peaceful fish of similar size. At feeding time, drop food in separate spots to avoid competition. Keep an isolation container, air pump, and heater on hand, and decide what to observe and when to see a vet after an injury.

Early on an October morning. A family member stepped on the escaped eel in a dark room. It was returned to the tank, but its body is bent in a V from the middle of the trunk, it lies on its side on the bottom, and it spins when it tries to swim. The gill covers are moving. There is no laceration, but the bent area is bulging.

Which is the most appropriate first action?

1. Push the bent area by hand to straighten it
2. Watch for a week, since it will heal on its own
3. Lower the water level, increase aeration, keep it quiet, and contact a vet who treats fish immediately
4. Increase the current to make it practice swimming

AnswerC. Lower the water level, increase aeration, keep it quiet, and contact a vet who treats fish immediately

ExplanationA body bent in a V, lying on its side and spinning, strongly suggests a spinal fracture or dislocation from being stepped on. All that can be done at home is to lower the water level so it does not exhaust itself trying to dive, increase aeration to secure oxygen, and turn off the lights to keep it quiet. Paralysis from spinal injury spreads over time, so contact a vet who treats fish immediately and have it seen. Pressing the bent area damages the nerves and worsens the paralysis. Left for a week, it cannot eat and weakens. A stronger current exhausts it and worsens the rolling.

IssuesOn top of inadequate escape prevention, walking through a dark room without checking the floor led to the trampling. The family had no rule for what to do when an eel might have escaped. The fact that this nocturnal fish escapes most often at night was not considered.

ImprovementPrevent escape with weights and netting on the lid. Agree as a family that if the lid is out of place, turn on the lights and check the floor before walking. Pick up an eel on the floor with wet hands. Learn the signs of spinal injury (bent body, on its side, spinning) so you can decide to see a vet immediately.

An April evening. On opening the bag of an eel delivered by mail order, the water is faintly red and cloudy and blood is seeping from between the gill covers. The bag is a single thin layer, and the water apparently dropped during transit, leaving part of the body exposed to air. The eel is writhing in the bag and its gill covers are moving rapidly. The bag water is 19°C; the tank is 25°C.

Which is the most appropriate first action?

1. Take it out of the water, open the gill covers to inspect them, and wipe away the blood
2. Because of the temperature difference, float the bag in the tank, then add tank water a little at a time over an hour to acclimate it, and consult a vet the same day about the gill bleeding
3. Release it into the tank right away and let it swim freely
4. Contact the carrier, then leave it in the bag until the next day for a return

AnswerB. Because of the temperature difference, float the bag in the tank, then add tank water a little at a time over an hour to acclimate it, and consult a vet the same day about the gill bleeding

ExplanationBleeding from the gills may mean internal or gill damage and is a sign of serious injury in a fish. However, there is a 6°C difference between the bag and the tank, so releasing it at once adds temperature shock. Float the bag in the tank to match the temperature, add tank water a little at a time over about an hour, then move it. For the gill bleeding, keep the water as clean as possible and consult a vet who treats fish the same day. Taking it out and opening the gill covers tears the delicate gills and worsens the bleeding. Immediate release causes temperature shock. Leaving it in the bag until the next day kills it through oxygen shortage and foul water.

IssuesThe purchase was made without checking the shipping method, and the eel was sent in a single thin bag. The owner had not researched acclimation or what to do about shipping problems. Nothing was ready for observing the fish on arrival (thermometer, isolation container).

ImprovementWhen buying live fish by mail order, confirm shipping in double bags with oxygen in an insulated box. On arrival, measure the bag water temperature and follow a set acclimation procedure. Observe new arrivals in a separate container for several days before adding them to the main tank, and consult a vet the same day if anything is abnormal. Contact the carrier after the fish has been cared for.

A June morning. The tank lid is slightly out of place and the 60 cm eel is nowhere in the tank. The pipe is empty too. The room is about 16 square meters (10 tatami mats), with gaps under furniture and along the walls, and the adjoining washroom has a floor drain. No one knows how many hours ago it escaped. A family member is about to start vacuuming.

Which is the most appropriate first action?

1. Vacuum and tidy the room first, then search
2. Go straight to the pet shop to buy a new one, since eels die on land
3. Stop the vacuuming, search dark corners, under furniture, and the drain in that order, and when found wrap it in a wet towel and return it to tank water
4. Sprinkle water on the floor and wait for it to come back on its own

AnswerC. Stop the vacuuming, search dark corners, under furniture, and the drain in that order, and when found wrap it in a wet towel and return it to tank water

ExplanationEels can breathe through their skin and, if kept moist, survive for hours and travel over land. After an escape, search under furniture, in dark damp places, and near drains; when found, wrap it in a wet towel, return it to a container of tank water, turn aeration to maximum, and wait for it to recover. Vacuuming can suck up or trample an eel under the furniture. Assuming it is dead is far too early. Sprinkling water on the floor will not bring it back to the tank and only wastes search time.

IssuesThe lid had no weights and left a gap it could get through. Despite the eel being nocturnal and most active at night, the lid was not checked before bed. The family had no search procedure for an escape.

ImprovementWeight the lid, seal holes for plumbing and cords with netting, and keep the water level at least 5 cm below the rim. Fit a cover on the floor drain. Agree as a family on the escape routine: turn on the lights, check your footing, search under furniture, then the drain; and decide where the wet towel and container are kept.

Late on a February night. A family member getting up to use the bathroom stepped on something in the dark hallway and screamed. With the lights on, the escaped eel is writhing in the hallway. The trunk where it was stepped on is slightly dented, but the skin is not torn. The hallway is cold with the heating off, and the eel's skin is starting to dry out.

Which is the most appropriate first action?

1. Return it to a container of tank water with wet hands, turn off the lights and observe for 30 minutes, and see a vet immediately if it stays on its side or keeps spinning
2. Grab it with dry hands and toss it into the tank
3. Leave it in the hallway and watch until the shock passes
4. Move it to a container of hot water to warm it

AnswerA. Return it to a container of tank water with wet hands, turn off the lights and observe for 30 minutes, and see a vet immediately if it stays on its side or keeps spinning

ExplanationA trampled eel may have internal or spinal injuries, and at the same time its skin breathing is near its limit from drying and cold. First lift it with wet hands, return it to a container of tank water, increase aeration, and turn off the lights to reduce stimulation. Observe for 30 minutes: if it swims and hides on its own, keep observing; if it stays on its side, spins, or remains bent, spinal injury is possible, so see a vet immediately. Dry hands strip the mucus, and tossing it in adds bruising. Left in the hallway, it dies of drying and cold. Hot water causes temperature shock and burns.

IssuesA double accident: a winter-night escape followed by trampling in a dark hallway. Lid management was lax, and there was no rule for walking around the house at night. In the unheated hallway, the skin was drying out, shortening the time it could survive.

ImprovementPrevent escape at the source with weights and netting on the lid. Use a hallway night light so family members do not walk in the dark. Make sure everyone knows to return an escaped eel to tank water with wet hands. Remember the signs after trampling that call for a vet (on its side, spinning, bent body).

An August night. The eel has pushed its head into the intake of a powerful canister filter and is stuck as if sucked on. It is thrashing its tail, and the skin of its neck at the edge of the intake is red. The strainer sponge was removed for cleaning and not put back. The gill covers are moving rapidly.

Which is the most appropriate first action?

1. Grab the tail and pull it out
2. Switch off the filter to release the suction, free it gently underwater, check the head and gills for damage, and see a vet immediately if anything is abnormal
3. Turn the filter output to maximum to reverse the flow
4. Wait several hours for it to free itself

AnswerB. Switch off the filter to release the suction, free it gently underwater, check the head and gills for damage, and see a vet immediately if anything is abnormal

ExplanationA fish sucked onto an intake will not come free until the suction stops. First switch off the filter to release the suction, then gently withdraw the head underwater. If the gills or head were sucked in, gill bleeding or damage is likely, so check gill cover movement and bleeding; if only one side moves, there is bleeding, or it lies on its side, see a vet immediately. Pulling the tail while the suction is on tears the neck and gills. Filters normally have no reverse function, and higher output only strengthens the suction. Left for hours, the gills are damaged and the fish suffocates.

IssuesThe strainer sponge was not put back, leaving the intake exposed. A powerful suction filter was used unprotected, without considering the eel's habit of pushing its head into holes and currents. There was no procedure for checking equipment after cleaning.

ImprovementAlways fit a sponge or netting on the intake, and after cleaning do a point-and-check of the intake, heater guard, and lid. Place the intake away from the pipe. Share with the family that for entrapment or suction accidents the rule is: switch off the power, free it underwater; and make the filter switch easy to find.

A September night. Water is seeping from a corner of the 90 cm tank and pooling on the floor. The water level has already dropped by half; the eel is in its pipe, but its back is nearly exposed to air. The crack seems to be spreading. The heater and filter are still running. On hand are a 45 cm spare tank and a plastic storage bin.

Which is the most appropriate first action?

1. Put waterproof tape over the crack and keep using the tank
2. Top up with tap water to maintain the level and wait until morning
3. Move the eel into the dry storage bin and repair the tank
4. Switch off the heater and filter, move the eel together with the tank water into the storage bin, and set up aeration and heating

AnswerD. Switch off the heater and filter, move the eel together with the tank water into the storage bin, and set up aeration and heating

ExplanationIf the heater becomes exposed as the water level drops, it can run dry or break and cause electric shock, so switch off the power first. Next, transfer as much of the remaining tank water as possible into the storage bin and move the eel in with its pipe. Using the tank water avoids water-quality shock. Secure oxygen and temperature with an air pump and heater (submerge the heater before switching it on), and place a board with weights on top as a makeshift lid. Waterproof tape cannot withstand the water pressure and the tank may collapse suddenly. Topping up with tap water causes shock from chlorine and the temperature difference. Moving the eel to a dry bin leaves it relying on skin breathing alone and is dangerous.

IssuesThe leak had progressed before the crack was noticed, endangering the floor and electrical equipment. A spare tank existed but was too small, and no emergency container or procedure had been decided. The stand's warping and the tank's aging had not been inspected.

ImprovementInspect the tank corners and silicone monthly and check that the stand is level. Keep a storage bin or large bucket empty as an emergency container and decide a procedure for transferring tank water. Mount power outlets high, and agree as a family that in a leak the first step is to cut the power.

A December night. On putting a hand into the tank, the owner feels a tingling in the fingertips. The eel is rigid and motionless in a corner of the tank, with only its gill covers moving rapidly. The heater's glass tube is cracked and the inside is charred black. The power strip for the tank sits on the floor, and the area around it is slightly wet.

Which is the most appropriate first action?

1. Quickly reach in and take the eel out
2. Pull the heater out of the water with bare hands
3. Film the eel and send the video to a vet
4. Without touching anything with wet hands, cut the breaker or unplug the power to stop the current, then check the fish and see a vet immediately if anything is abnormal

AnswerD. Without touching anything with wet hands, cut the breaker or unplug the power to stop the current, then check the fish and see a vet immediately if anything is abnormal

ExplanationA heater with a broken glass tube leaks current into the water and can electrocute both people and fish. If you feel tingling, do not put your hand in the water; with dry hands, switch off the breaker or unplug to stop the current. Then check the fish's response; if rigidity, lying on its side, or abnormal gill movement continues, see a vet immediately. Reaching in or pulling out the heater while the power is on can cause a serious electric shock to a person. Filming leaves the current on and both fish and people in danger. A heater switched on out of the water will crack, so review how it is handled during cleaning too.

IssuesThe heater's glass tube had deteriorated or cracked and was kept in use unnoticed. The power strip was on the floor where it could get wet. No strip with a ground-fault (earth-leakage) breaker was used. The owner did not know the correct procedure after feeling a sign of electric shock (tingling).

ImprovementReplace the heater every 1–2 years and never switch it on out of the water. Fix the power strip above the tank and use one with a ground-fault breaker. Agree as a family that if you feel tingling, do not reach in; cut the breaker. Make sure everyone knows where the breaker is.

A May afternoon. The owner was giving the tank a thorough cleaning in the bathroom. The eel was in a bucket but jumped out, slid across the floor, and went headfirst into the bathroom floor drain. About 10 cm of tail sticks out of the drain and is moving. The drain cover had been removed. Running water might wash it away, and pulling might injure it.

Which is the most appropriate first action?

1. Check whether the drain trap can be removed; if so, dismantle it and retrieve the eel underwater; if not, hold the tail with wet hands and wait for it to back out on its own
2. Run the shower to push it out
3. Grab the tail and pull it out by force
4. Let it be washed away to return to nature

AnswerA. Check whether the drain trap can be removed; if so, dismantle it and retrieve the eel underwater; if not, hold the tail with wet hands and wait for it to back out on its own

ExplanationEels instinctively push headfirst into narrow holes, and a drain is an ideal escape route. Pulling by force tears the skin and injures the spine. First check whether the drain trap is removable; if so, dismantle it over a container of water and take the fish out. If not, hold the tail lightly with wet hands and wait for it to back out. Afterward check for wounds and a bent body, and consult a vet the same day if anything is abnormal. Running water flushes it into the sewer, and letting it out alive into the environment is the same as releasing it, which is not permitted. Pulling causes serious injury. Leaving it loses the fish and amounts to releasing it into the sewer.

IssuesThe eel was kept in an open bucket in the bathroom with the drain cover removed. Two habits, jumping out and entering holes, were not considered. A cleaning method that did not require removing the fish was not chosen.

ImprovementClean with partial water changes without removing the fish. When it must be removed, use a lidded container and work with the drain cover closed. In the bathroom, keep the floor wet to prevent drying. Share with the family the principle that a kept fish is never let out into the sewer or a river.

A March night. The family cat climbed onto the tank lid, which flexed and fell into the water. The glass lid broke and shards are scattered on the tank bottom. The startled eel has bolted from its pipe and is thrashing around the tank. The cat still has its front paws on the rim and is peering in. The top of the tank is open.

Which is the most appropriate first action?

1. Chase the cat away, then reach in and quickly pick up the shards
2. Keep the lights on and watch until the eel calms down
3. Drain all the water along with the shards and wash the tank out
4. Put the cat in another room, cover the tank with a board and weights, turn off the lights to calm the eel, then carefully collect the shards with a net

AnswerD. Put the cat in another room, cover the tank with a board and weights, turn off the lights to calm the eel, then carefully collect the shards with a net

ExplanationFirst put the cat in another room to prevent another accident and predation, and cover the top of the tank with a board or netting and weights so the thrashing eel cannot jump out. Turning off the lights and keeping quiet stops the thrashing. Collect the shards with a net or tweezers, not your hands, and remove fine fragments together with the substrate. Check the eel's skin for cuts; if any, keep the water as clean as possible and observe. Reaching in while the cat is nearby risks a jumping fish being caught by the cat. With the lights on, the eel keeps thrashing and may be cut by the shards. A full water change adds water-quality shock.

IssuesThe tank was somewhere the cat could climb, and the lid was glass with no weights. Cats react strongly to moving water and fish, and the possibility of the cat climbing on the lid was not anticipated. The escape precautions vanished when the lid broke.

ImprovementUse an unbreakable acrylic or wire-mesh lid secured with weights and clips. Do not place shelves or objects over the tank that the cat can climb, and keep the cat out of the tank room. Keep a spare lid and a board nearby that can cover the tank immediately if the lid breaks.

A July afternoon. A 5-year-old opened the lid and lifted the eel out with bare hands. It slipped out and fell to the floor, where it is writhing. The child is crying and trying to grab it again. There is a patch on the eel's skin where the mucus has come off and turned white, and dust from the floor is stuck to it. The tank is right beside it.

Which is the most appropriate first action?

1. Have the child pick it up and return it to the tank
2. Wipe the dust off with a dry cloth before returning it
3. Move the child away, lift the eel with wet hands into a container of tank water, rinse off the dust with tank water, and observe
4. Assume it will get sick from the floor and give it a medicated bath right away

AnswerC. Move the child away, lift the eel with wet hands into a container of tank water, rinse off the dust with tank water, and observe

ExplanationFirst move the child away to prevent a second accident. Lift the eel with wet hands supporting the trunk and return it to the tank or a container of tank water. Rinse off the dust with tank water; do not brush it off by hand. Then observe for 30 minutes for lying on its side or spinning and consult a vet the same day if anything is abnormal. Watch the patch without mucus for several days for cotton-like growth or redness. Letting the child pick it up risks another drop or a tight grip that damages the organs. A dry cloth strips more mucus. A medicated bath with no symptoms is only a burden.

IssuesThe lid could be opened by a child alone, and there was no rule against touching animals with bare hands. The child had not been taught that eels are slippery and easy to drop. The tank was at a height the child could reach.

ImprovementFit the lid with weights and a lock so a child cannot open it alone. Teach that fish are for looking at, not touching, and that any handling is done with an adult, with wet hands. Share the response to a drop (wet hands, tank water, observation) as a family. Place the tank on a stand above the child's eye level.

An August evening. Because evaporation had lowered the water level, the owner added two buckets of tap water straight into the tank. Ten minutes later, the eel is swimming violently around the tank and its mucus has started to turn cloudy white and drift off. The gill covers are moving rapidly. The dechlorinator has run out and there is none on hand. The nearby shop is closed.

Which is the most appropriate first action?

1. Turn off the lights and do nothing until the thrashing stops
2. Add more tap water to dilute it
3. Take the fish out and put it in a separate bucket of tap water
4. Turn aeration to maximum, do a 1/3 water change with water that has been left standing or boiled and cooled, and see a vet if mucus or breathing problems continue the next day or later

AnswerD. Turn aeration to maximum, do a 1/3 water change with water that has been left standing or boiled and cooled, and see a vet if mucus or breathing problems continue the next day or later

ExplanationThe chlorine in tap water damages the mucous membranes of the gills and skin; violent swimming and clouded mucus are signs of this poisoning. Without a dechlorinator, turn aeration to maximum to drive off chlorine and supply oxygen, and do a 1/3 water change with water that has stood overnight or been boiled and cooled to lower the chlorine level. Gill damage appears over several days, so if breathing is still rapid or the mucus is still peeling the next day or later, see a vet the same day. Doing nothing lets the gill damage progress. More tap water adds more chlorine. Putting it in another bucket of tap water is the worst option.

IssuesTop-up water was added while the dechlorinator had run out, underestimating the harm of chlorine. The basic rule that even top-up water must be dechlorinated was skipped. The owner did not fully understand that the eel, with vestigial scales, is especially sensitive to chlorine and other chemicals.

ImprovementKeep a spare bottle of dechlorinator and check the remaining amount monthly. Always have a bucket of aged water ready for topping up. Write the water change and top-up procedure on paper and post it beside the tank. Learn the signs of chlorine poisoning (thrashing, clouded mucus, rapid breathing) and when to see a vet.

An April afternoon. While wiping the outside glass of the tank with dish detergent, foam from the sponge fell through a gap in the lid into the tank. Foam has spread over the surface, and the eel is gasping near the surface and writhing. The amount is about one squeeze of a sponge; the tank holds 90 L of water. There is 30 L of aged water in reserve.

Which is the most appropriate first action?

1. Remove the foam, change as much water as possible with the aged water, turn aeration to maximum, watch the breathing and mucus, and see a vet the same day if problems continue
2. Leave it, since a small amount of foam will disappear on its own
3. Add a large amount of activated carbon and skip the water change
4. Wash the fish with a different detergent and return it to the tank

AnswerA. Remove the foam, change as much water as possible with the aged water, turn aeration to maximum, watch the breathing and mucus, and see a vet the same day if problems continue

ExplanationThe surfactants in detergent destroy the gill membranes and directly impair breathing. First skim the foam from the surface with a net or paper towel, then change as much water as possible with the aged water to lower the concentration. Turn aeration to maximum to supply oxygen, and do another water change the next day. If gasping, peeling mucus, or lying on its side continues, see a vet the same day. Even a small amount has a large effect on the gills, so leaving it is dangerous. Activated carbon helps but is no substitute for a water change. Washing the fish with detergent is fatal.

IssuesDetergent was used next to the tank while the lid had a gap. The risk of using chemicals around the tank was not considered. Only 30 L of aged water was on hand, so an adequate water change was not possible.

ImprovementWipe the tank glass with water only, and do not use detergents, air fresheners, or insecticides in the tank room. Keep lid gaps sealed at all times. Keep aged water on hand equal to about half the tank volume. Decide in advance the order of action for contamination: remove, change water, aerate.

A June night. A cockroach spray was used in the room with the tank. Thirty minutes later, the eel is lying on its side on the bottom, trembling in small spasms. The gill covers are moving rapidly but weakly. An oily film is visible on the surface. The lid is mesh, and the air pump is pumping the room's air into the water.

Which is the most appropriate first action?

1. Assume insecticide only affects insects and is unrelated, and wait
2. Increase aeration in the same room to send more oxygen
3. Skim off the film, then spray insecticide again to kill the insects that caused it
4. Open the windows to ventilate, move the air pump where it can draw air from another room, change water with aged water, and see a vet immediately if it stays on its side

AnswerD. Open the windows to ventilate, move the air pump where it can draw air from another room, change water with aged water, and see a vet immediately if it stays on its side

ExplanationMost insecticides are highly toxic to fish; airborne chemicals dissolve in through the surface, and the air pump accelerates the poisoning by pumping the room's air into the water. First open the windows to ventilate and move the air pump where it can draw clean air from another room, or pause it. Remove the film from the surface, change water with aged water, and if lying on its side or convulsions continue, see a vet immediately for the effects of the neurotoxin. Insecticide acts on fish too, so waiting is fatal. More aeration with the room's air keeps delivering the poison. Spraying again is out of the question.

IssuesInsecticide spray was used in the tank room without understanding that the mesh lid and air pump would draw the chemical in. The owner did not know that fish are sensitive even to airborne chemicals and that insecticides in particular are lethal.

ImprovementDo not use insecticides, foggers, air fresheners, or disinfectant sprays in the tank room. If unavoidable, seal the tank, stop the air pump, and move it to another room. Keep aged water on hand, and for poisoning follow the order: ventilate, secure a clean air source, change water.

An October night. The owner has several times seen the eel swallow large gravel along with its food. For about 5 days its belly has been swollen and it has not passed feces. It tries to eat but spits the food out. Water quality is normal and the water is 25°C. The substrate is angular gravel about 1 cm in size, and food is given by sinking it to the bottom. The skin is normal.

Which is the most appropriate first action?

1. Press on the belly to make it spit out the gravel
2. Stop feeding, switch the gravel to fine sand or a bare tank, record the belly swelling and bowel movements, and see a vet within a few days
3. Mix a human digestive aid into its food as a laxative
4. Let it keep eating gravel, since it will be digested

AnswerB. Stop feeding, switch the gravel to fine sand or a bare tank, record the belly swelling and bowel movements, and see a vet within a few days

ExplanationSwallowing large gravel with food, followed by ongoing abdominal swelling and no feces, suggests a blockage of the digestive tract. First stop feeding to reduce the load, and switch the gravel to smooth fine sand or a bare tank to prevent further ingestion. Record the belly swelling and bowel movements daily and have a vet who treats fish examine it within a few days. If it regurgitates food, lies on its side, or the vent swells, see a vet the same day. Pressing the belly can rupture the digestive tract. Human medication is dangerous because the dose is unknown. Gravel is not digested and stays stuck.

IssuesAngular, large gravel was used as substrate and food was given on the bottom, inviting ingestion. The substrate was not changed even after the eel was seen swallowing gravel. The signs of a blockage (swollen belly, no feces, regurgitation) were overlooked for several days.

ImprovementUse smooth fine sand or a bare tank. Put food in a feeding dish or offer it mid-water with tweezers to keep it separate from the gravel. Record bowel movements weekly; if none for 3 days or more, check the water temperature, food, and belly. Do not treat ingested foreign objects at home; see a vet.

A February night. The owner moved an eel with white spots on its body to a separate container and began a salt bath based on information found online. Feeling it was not working well, the owner added more salt to raise the concentration; 30 minutes later the eel has stopped moving on the bottom of the container, its gill covers barely move, and large amounts of mucus are peeling off. There is 20 L of tank water on hand.

Which is the most appropriate first action?

1. Continue the salt bath, since this proves it is working
2. Add even more salt to kill the parasites in one go
3. Add tap water straight from the tap to dilute it
4. Slowly lower the concentration with tank water, turn aeration to maximum, and contact a vet who treats fish immediately if it does not recover

AnswerD. Slowly lower the concentration with tank water, turn aeration to maximum, and contact a vet who treats fish immediately if it does not recover

ExplanationThe eel's vestigial scales let salt and chemicals enter through the skin easily; in a strong salt bath the mucus peels off and osmotic stress leaves it unable to move. Immediately add tank water a little at a time to lower the salinity, and turn aeration to maximum to supply oxygen. If it does not recover and keeps lying on its side or the gill movement stays weak, contact a vet who treats fish immediately. Salt baths should be done under a vet's instructions at the proper concentration and duration. Maintaining or adding salt will kill it. Diluting with tap water adds chlorine poisoning.

IssuesThe salt bath was started on the basis of online information alone, and salt was added by feel without measuring the concentration. The owner did not know that the eel is sensitive to salt and chemicals. The step of consulting a vet who treats fish before treatment was skipped.

ImprovementConsult a vet who treats fish before starting any treatment, and measure and follow the concentration and duration. Start salt or medication at a low dose and watch the fish's reaction. During treatment, check gill movement and the mucus every 30 minutes, and be ready to return it to tank water immediately if anything is abnormal.

An August afternoon. In a closed-up room, the tank water has risen to 33°C. The eel has left its pipe and hangs motionless near the surface, its gill covers moving rapidly. The cooling fan is running but ineffective. The air conditioner is broken and will not be repaired until tomorrow. The freezer has ice packs and frozen water bottles, and there is 30 L of aged water at room temperature.

Which is the most appropriate first action?

1. Drop ice straight into the tank to cool it quickly
2. Remove the entire lid to expose the water to air
3. Turn aeration to maximum, float frozen water bottles in bags, and lower the temperature to 28°C or below at a rate of about 1°C per hour
4. Feed extra to build up its strength until the temperature drops

AnswerC. Turn aeration to maximum, float frozen water bottles in bags, and lower the temperature to 28°C or below at a rate of about 1°C per hour

ExplanationWater above 30°C is close to the eel's limit, and at high temperatures dissolved oxygen falls, making breathing difficult. First turn aeration to maximum to supply oxygen, then float frozen water bottles in bags and lower the temperature slowly, about 1°C per hour, to 28°C or below. Turn off the lights and ventilate the room. Dropping ice in directly causes a sudden temperature drop and shock, and alters the water chemistry. Removing the lid raises the risk of escape. Feeding at high temperatures cannot be digested and degrades the water.

IssuesThe only summer measure was a cooling fan, with no backup for the unexpected failure of the air conditioner. The rise in water temperature went unnoticed until the afternoon, allowing it to reach 33°C. There was no serious cooling equipment such as an aquarium chiller.

ImprovementInstall an aquarium chiller for summer and use the fan as a supplement. Use a thermometer with an alarm set to alert at 28°C. Always keep several frozen water bottles ready and write out the emergency cooling procedure. Have the air conditioner serviced before summer.

A January night. Heavy snow has caused a power outage, and the heater, filter, and air pump have all stopped. There is no word on when power will be restored. The room has dropped to 10°C, and the water is starting to fall from 24°C. The eel is in its pipe. On hand are blankets, a foam box, a battery-powered air pump, and a portable gas stove with a pot.

Which is the most appropriate first action?

1. Boil water on the gas stove and pour it directly into the tank to warm it
2. Open the lid to let in room air and prevent oxygen shortage
3. Do nothing in particular and wait for the power to return
4. Run the battery air pump, wrap the tank in blankets and foam, and float bottles of hot water to slow the drop in temperature

AnswerD. Run the battery air pump, wrap the tank in blankets and foam, and float bottles of hot water to slow the drop in temperature

ExplanationIn a power outage the priorities are oxygen and warmth. First run the battery air pump to supply oxygen, then cover the whole tank with blankets and foam to reduce heat loss. Float bottles of hot water in bags and replace them every 1–2 hours to slow the drop in water temperature. The goal is to avoid a sudden drop; if it stabilizes around 15°C, the eel can hold on for several days. Pouring in boiling water causes local burns and temperature shock. Opening the lid does not add oxygen; it invites escape and heat loss. Doing nothing lets the water fall into the low teens within hours, lowering immunity and inviting red spot disease and the like.

IssuesThere had been no preparation for a winter power outage; having a battery air pump was lucky. No insulation had been prepared and no outage procedure decided. The owner relied on a single heater with no passive insulation measures.

ImprovementKeep a battery air pump with spare batteries, foam boards, and insulating sheets beside the tank. Write out the outage procedure (air pump, cover, hot-water bottles) and post it. Fit permanent insulation on the back and sides of the tank to reduce winter heat loss. After power returns, check that the heater restarts and verify the water temperature.

Late at night, an earthquake of seismic intensity 5 has sloshed a third of the water out of the tank and shifted the tank several centimeters on its stand. The lid has fallen to the floor, and the heater is half exposed above the surface. The eel is swimming violently around the tank. The filter is making a dry-running noise. Aftershocks continue. The floor is soaked and the power strip is nearby.

Which is the most appropriate first action?

1. Cut the power, prevent escape with the lid and weights, and once things settle, restore the water level with aged water and move the shifted tank back to a safe position
2. Push the tank back into place first
3. Top up with tap water right away to restore the level
4. Move the eel to a bucket and deal with the tank later

AnswerA. Cut the power, prevent escape with the lid and weights, and once things settle, restore the water level with aged water and move the shifted tank back to a safe position

ExplanationFirst cut the power to prevent electric shock and dry running. An exposed heater will crack and leak current if powered. Next, replace the fallen lid and put weights on it to stop the agitated eel from jumping out. Once the aftershocks subside, restore the water level with aged water, and either lower the water and move the shifted tank back to the center of the stand or take measures against tipping. Working on a wet floor without cutting the power risks electrocution. Pushing the tank first risks breakage or further tipping. Topping up with tap water causes shock from chlorine and the temperature difference. In a bucket without a lid it will jump out; the tank is safer.

IssuesThe anti-tipping measures and the position of the power supply had not been planned for an earthquake. The lid had no weights and fell off in the shaking. Aged water and outage supplies were ready, but no earthquake procedure (power, lid, water level in that order) had been decided.

ImprovementAnchor the stand to the wall and use a non-slip mat. Fix the power strip above the tank. Secure the lid with clips and weights so it cannot fall, and keep the water level at least 5 cm below the rim. Share the post-earthquake procedure as a family and keep aged water and a battery air pump on hand.

A September night. An evacuation order has been issued because of a typhoon, and the family will drive an hour to a relative's house. They want to take the 70 cm eel. On hand are thick plastic bags, a foam box, a bucket, and a battery air pump. It is raining outside and 25°C. There is plenty of tank water. The family is in a hurry and about to fill the bucket with tap water.

Which is the most appropriate first action?

1. Put the eel in a bucket of tap water and set it on the passenger seat
2. Wrap the eel alone in a wet towel and carry it
3. Load the whole tank, water and all, into the car
4. Put 1/3 tank water and air in a thick bag, double-bag and tie it, place it in the foam box to keep it dark, and set it in the footwell where there is least motion

AnswerD. Put 1/3 tank water and air in a thick bag, double-bag and tie it, place it in the foam box to keep it dark, and set it in the footwell where there is least motion

ExplanationThe basic method for short fish transport is a thick bag with 1/3 tank water and 2/3 air, double-bagged and tied tightly, placed in a foam box to keep it dark and insulated. Tank water avoids water-quality shock, and the air in the bag provides enough oxygen for about an hour. Place the box in the footwell where there is least motion. At the destination, use the battery air pump and move it to a larger container once settled. Tap water causes chlorine shock, and it will jump out of an open bucket. A wet towel alone forces it to rely on skin breathing for a long time, with danger from drying and thrashing. Loading the whole tank risks breakage.

IssuesNo evacuation transport procedure had been decided, and the family nearly chose the dangerous method of a bucket of tap water. The bags and foam box were available, but the family did not know how to use them. Preparations for continuing to keep the eel at the destination (container, air pump) had not been considered.

ImprovementAssemble an evacuation kit of thick bags, rubber bands, a foam box, and a battery air pump, with the bagging procedure written on paper inside. Practice bagging once a year. Prepare a collapsible container for use at the destination. Make sure the whole family understands that in an emergency the eel is carried in tank water.

A January morning. The indoor tank, kept unheated at around 15°C for winter dormancy, has dropped to 8°C overnight in a cold snap. The eel is completely still in its pipe and responds sluggishly to touch. The gill covers are moving very slowly. It has not been fed since December. The daytime room temperature is expected to reach only 12°C.

Which is the most appropriate first action?

1. Quickly raise it to 25°C with a heater to wake it up
2. Add a heater, bring the water back to around 15°C at 1–2°C per day, wrap the tank in insulation, and observe without feeding
3. Assume it is dying because it responds sluggishly, and warm it with hot water
4. Feed it to build up its strength, since it has not been eating

AnswerB. Add a heater, bring the water back to around 15°C at 1–2°C per day, wrap the tank in insulation, and observe without feeding

ExplanationIn dormancy management, stability around 15°C is essential; at 8°C, physiological functions decline and the eel enters a danger zone. But warming it suddenly causes temperature shock and an abrupt change in metabolism, so add a heater and bring the water back to around 15°C at 1–2°C per day, and wrap the tank in insulation to prevent another drop. It cannot digest at low temperatures, so do not feed. If the gill covers stop moving or it lies on its side, consult a vet the same day. A rapid rise to 25°C causes shock. Hot water causes local burns and sudden change. Food rots in the gut and can be fatal.

IssuesDespite choosing dormancy management, there was no preparation for a cold snap taking the room below expectations. No backup heater or insulation had been prepared to maintain a minimum water temperature even without active heating. The lower limit (around 15°C) and how to maintain it were not fully understood.

ImprovementEven during dormancy, use a backup heater so the water does not fall below 12°C, and record the temperature morning and evening. When a cold snap is forecast, wrap the tank in insulation the day before. Do not feed during dormancy, and maintain water quality with a small monthly water change. If unsure about dormancy management, keep it normally at 22°C or above with a heater.

A July night. The owner cleaned the tank bare-handed yesterday, ignoring a small cut on a finger. Since this morning the cut has become red, swollen, and hot, and a red streak is extending up the arm. There is also a fever of 38°C. The owner is being treated for diabetes. The eel is kept in near-brackish water and is itself healthy.

Which is the most appropriate first action?

1. Apply an over-the-counter ointment and wait
2. Give the eel a medicated bath and disinfect the tank
3. Squeeze the pus out of the wound and bandage it
4. See a doctor immediately and report the possible infection through a wound during aquarium work and the diabetes

AnswerD. See a doctor immediately and report the possible infection through a wound during aquarium work and the diabetes

ExplanationAquarium water contains bacteria such as Vibrio, Edwardsiella, and Aeromonas that can infect people through wounds. Swelling, heat, a red streak (lymphangitis), and fever are signs the infection is spreading, and in people with diabetes or liver disease it can become severe and life-threatening. See a doctor immediately and be sure to mention the aquarium work and the underlying condition. This is a human emergency; the fish's medicated bath and tank disinfection can wait. Waiting with over-the-counter medication or squeezing the wound spreads the infection and loses time.

IssuesThe owner worked without gloves despite a cut on the hand and underestimated diabetes as a risk factor for severe illness. They did not know that aquarium water contains bacteria that infect human wounds, nor that brackish-water keeping carries a higher risk of Vibrio.

ImprovementWear long gloves for tank work, and do not work when there is a cut on your hand. Wash hands with soap afterward. People with diabetes, liver disease, or weakened immunity must always wear gloves and should decide in advance to see a doctor immediately if a wound swells. Mentioning the fish tank at the visit leads to the right treatment.

March. A house move means there is no room for the large tank, and the 75 cm eel kept for 5 years must be given up. The family says that since it is originally a Japanese fish, releasing it in the nearby river would return it to nature. This eel previously had white spot disease, and after treatment its tankmates also fell ill. The move is in 2 weeks.

Which is the most appropriate first action?

1. Release it in the nearby river to return it to nature
2. Release it at an estuary near the sea, since that would be fine
3. Do not release it; look for someone to take it in, such as the shop of purchase, a vet who treats fish, an aquarium, or an experienced keeper
4. Do nothing until moving day and decide then

AnswerC. Do not release it; look for someone to take it in, such as the shop of purchase, a vet who treats fish, an aquarium, or an experienced keeper

ExplanationReleasing a captive fish spreads pathogens and parasites brought into the tank to wild fish, and farm-raised individuals disrupt the genetic makeup of wild populations. The Japanese eel is an endangered species and release also violates local fishery regulations, so it is not permitted anywhere. Use the 2 weeks to ask the shop of purchase, a vet who treats fish, an aquarium, or a keepers' group to take it in. Release at an estuary causes the same problems. Putting it off until the day leaves no options and ends in release or abandonment. Abandoning an animal is also prohibited under the Act on Welfare and Management of Animals.

IssuesWhen taking in a long-lived fish that grows large, the owner did not plan for life changes such as moving. The family did not understand that release spreads pathogens and harms an endangered species. No information on who could take it in had been gathered in advance.

ImprovementWhen starting, set up to keep it for 10–20 years and decide who could take it in if that becomes impossible. Agree as a family that release is never an option. Ask the shop of purchase whether they will take it back, and keep the contact details of a vet who treats fish and an aquarium. Reconsider ways to place a tank at the new home.

A May night. An eel with white spot disease is being treated in a quarantine tank. The owner realizes the same net and pipette have been used for both the quarantine tank and the main tank. The main tank holds a healthy eel and small fish. One of the small fish seems to have a tiny white spot on a fin. It is day 3 of treatment in the quarantine tank and the white spots are decreasing.

Which is the most appropriate first action?

1. Separate the equipment for each tank, check every fish in the main tank daily, and if white spots are confirmed, raise the main tank's temperature, change water, and consult a vet
2. Return the quarantined fish to the main tank and treat everyone together
3. Release the small fish from the main tank into a river to reduce the source of infection
4. Add a double dose of the quarantine tank's medication to the main tank as a precaution

AnswerA. Separate the equipment for each tank, check every fish in the main tank daily, and if white spots are confirmed, raise the main tank's temperature, change water, and consult a vet

ExplanationThe white spot parasite can travel in the water droplets on equipment. First separate nets, pipettes, and buckets for each tank, and wash and dry used equipment. Check every fish in the main tank daily under a light; if white spots are confirmed, raise the main tank's temperature 1°C per day, change water daily, and consult a vet for treatment. A double dose at the stage of mere suspicion is an undiagnosed overdose and is highly toxic to a scaleless eel. Returning the fish under treatment adds a source of infection. Releasing the small fish puts pathogens into the environment and is the worst possible action.

IssuesThe owner did not understand the purpose of quarantine and left a transmission route by sharing equipment. Knowledge of basic quarantine practice (separate equipment, handwashing, observation) was lacking. Observation of the main tank was vague, and the presence of white spots was not clearly confirmed.

ImprovementPrepare color-coded nets, pipettes, and buckets for each tank. Do the quarantine tank last and wash hands afterward. Check the skin of every fish in the main tank each night under a light and record whether white spots are present. Consult a vet for treatment, follow the dose, and do not medicate as a precaution.

November. The owner has cleaned the eel's tank bare-handed for 2 years. Three months ago a small reddish-purple lump appeared on the back of the right hand, and more have gradually appeared in a line toward the elbow. The pain is mild, and over-the-counter ointment does not help. A dermatologist said the cause was unknown, but the owner did not mention keeping fish.

Which is the most appropriate first action?

1. Stop keeping the eel and release it in a river, since it may be the cause
2. Switch to an over-the-counter antifungal and wait another month
3. Lance the lumps with a needle and squeeze out the contents
4. Go back to the dermatologist, explain that you clean a fish tank bare-handed, and get specialized testing

AnswerD. Go back to the dermatologist, explain that you clean a fish tank bare-handed, and get specialized testing

ExplanationReddish-purple lumps that do not heal and spread in a line from the hand up the arm suggest fish tank granuloma (Mycobacterium marinum infection), caused by mycobacteria in the tank entering through a wound. It is hard to detect with routine tests; telling the doctor that you handle a fish tank bare-handed leads to the diagnosis. Treatment requires several months of oral medication, and it spreads if left untreated. Waiting with over-the-counter medication loses time. Lancing with a needle spreads the infection. There is no need to stop keeping the eel, and release is never an option. Wearing gloves prevents it.

IssuesHandling the tank bare-handed for 2 years let bacteria enter through small wounds. The dermatologist was not told about contact with fish, delaying the diagnosis. The owner did not know about zoonotic infections or the importance of mentioning animal contact at a medical visit.

ImprovementAlways wear long gloves for tank work. Do not work when there is a cut on your hand. When seeing a doctor for skin or health problems, always mention the animals you keep and how you handle them. Make it a habit to connect a non-healing swelling or lump on the hand with the fish tank.

A February morning. In a tank at 22°C, the eel is completely motionless in its pipe. It did not eat last night's food. It does not move under a light and its body looks slightly pale. The family says it is dead and is about to take it out and bury it. No one has checked whether the gill covers are moving. The water was tested last week and was normal.

Which is the most appropriate first action?

1. Decide it is dead because it is not moving, remove it, and dispose of it
2. Check gill cover movement and its response to a light touch; if alive, test the water, increase aeration, and observe
3. Take it out of the tank and give it cardiac massage
4. Bang on the water to startle it, and give up if there is no response

AnswerB. Check gill cover movement and its response to a light touch; if alive, test the water, increase aeration, and observe

ExplanationEels barely move during the day, and rest for long periods especially at cooler temperatures. Death is judged by gill cover movement and response to stimulation. At rest the gill covers move about 40–80 times a minute; if they move at all, even faintly, it is alive. If it flinches away from a light touch, that is within normal. If it is unresponsive, on its side, and the paleness is spreading, it is in critical condition: test the water, turn aeration to maximum, and consult a vet the same day. Disposing of it just because it is not moving means killing a living fish. Cardiac massage has no effect on fish, and taking it out of the water makes things worse. Banging on the water is stress from the impact.

IssuesThe daytime stillness of a nocturnal eel was mistaken for something abnormal. Not knowing how to confirm life or death (gill covers, response), the family rushed to dispose of it. When it did not eat, the water temperature, water quality, and skin were not checked.

ImprovementAgree as a family to judge life and severity by three things: gill cover movement, response to stimulation, and body color. Count and record the normal gill cover rate as a baseline for comparison. The day after it refuses food, always check water temperature, water quality, and the skin. Before deciding it is dead, phone a vet who treats fish.

Late on a June night. The owner found the eel on the floor after it jumped out and returned it to the tank with wet hands. But it lies on its side on the bottom and cannot swim on its own. The gill covers are moving, though slowly. The skin is still moist, with dust stuck on in places. The tank has a single weak air pump. The water is 26°C and the water quality is normal.

Which is the most appropriate first action?

1. Decide it will die since it is on its side, and do nothing
2. Take it out of the tank, stretch the body, and massage it to improve circulation
3. Wash the dust off under tap water before returning it
4. Turn aeration to maximum, hold it underwater with the head forward and move it gently back and forth so water flows through the gills, turn off the lights, and wait for it to recover

AnswerD. Turn aeration to maximum, hold it underwater with the head forward and move it gently back and forth so water flows through the gills, turn off the lights, and wait for it to recover

ExplanationLying on its side after jumping out means it is weakened by drying and oxygen shortage. Fish are resuscitated in the water. Turn aeration to maximum to increase oxygen, and hold it underwater with the head forward, moving it gently back and forth so water flows through the gills and aids breathing. Rinse off the dust with tank water. Turn off the lights and keep quiet; if it swims on its own within 30 minutes to an hour, keep observing; if the gill movement stops or it stays on its side, see a vet immediately. Doing nothing throws away the chance of recovery. Out of the water it can only breathe through its skin and gets worse. Tap water's chlorine damages the gills.

IssuesPoor lid management led to the escape, and the weak air pump could not supply enough oxygen in the emergency. The owner did not know fish resuscitation (pass water through the gills underwater) and tended to think of mammal-style first aid.

ImprovementPrevent escape with weights and netting on the lid. Have an air pump with spare capacity plus a backup. Share fish resuscitation as a family: in the water, aeration at maximum, water through the gills, dark and quiet. Decide the recovery benchmark (swimming on its own within 30 minutes to an hour) and when to see a vet.

An April night. The eel cut its flank on a fragment of a broken heater guard and is swimming around the tank trailing blood. The cut is about 3 cm long and continues to bleed enough to tint the surrounding water faintly red. The gill covers are moving normally and it can swim. The house has a human styptic and disinfectant.

Which is the most appropriate first action?

1. Remove the fragment, keep the fish in the water with the water as clean as possible to prevent secondary infection, and consult a vet the same day if the bleeding lasts several hours or it weakens
2. Take it out of the water and apply the human styptic to the wound
3. Hold the fish in your hand and squeeze to press on the wound
4. Add disinfectant to the tank to sterilize it

AnswerA. Remove the fragment, keep the fish in the water with the water as clean as possible to prevent secondary infection, and consult a vet the same day if the bleeding lasts several hours or it weakens

ExplanationBleeding in fish is managed in the water as a rule; out of the water the mucus comes off and it is left relying on skin breathing. First remove the fragment that caused it, then do a water change to keep the water as clean as possible and prevent bacterial infection of the wound. A shallow cut stops on its own as the mucus regenerates. If the bleeding continues for several hours, the swimming weakens, or there is bleeding from the gills or mouth, internal injury is possible, so consult a vet the same day. A human styptic has no effect underwater and the chemicals foul the water. Squeezing strips the mucus and enlarges the wound. Disinfectant damages the gills and kills the fish. Wear gloves during the work so eel blood does not get into your eyes or wounds.

IssuesThe broken heater guard was not replaced, leaving a sharp fragment in the tank. Equipment inspection was inadequate, and not knowing the principle of fish bleeding control (in the water, through water management), the owner could have used human medication. The toxin in eel blood was not kept in mind either.

ImprovementInspect equipment monthly and replace anything cracked or chipped immediately. Remember bleeding control for fish as: do not take it out, keep the water clean, do not touch. Use gloves and protective glasses when handling a bleeding fish. Decide the signs that call for a vet (bleeding for several hours, bleeding from the gills or mouth, weakening).

An October afternoon. Because of a swollen vent and a bloated belly, a same-day visit to a vet who treats fish has been arranged. The drive takes 40 minutes. On hand are thick plastic bags, rubber bands, a foam box, and a bucket. The water is 25°C and the outside air 18°C. The owner is hurriedly about to fill the bucket with tank water to carry it.

Which is the most appropriate first action?

1. Put tank water in the bucket and carry it uncovered on the floor of the passenger seat
2. Wrap it in a wet towel and carry it on your lap
3. Put 1/3 tank water and air in a thick bag, double-bag and tie it, keep it warm and dark in the foam box, carry it without jolting, and bring water-test data and photos
4. Put tap water in the bucket and carry it

AnswerC. Put 1/3 tank water and air in a thick bag, double-bag and tie it, keep it warm and dark in the foam box, carry it without jolting, and bring water-test data and photos

ExplanationFor a 40-minute trip, put 1/3 tank water and 2/3 air in a thick bag, double-bag it, tie it tightly with rubber bands, and place it in a foam box. The dark box calms the eel and holds the water temperature despite the difference from the outside air. Set the box in the footwell where there is least motion. Bring the water temperature, pH, ammonia, and nitrite readings, the date of the last water change, and photos of the symptoms. An open bucket invites jumping out, splashing, and a drop in temperature. A wet towel alone forces it to rely on skin breathing for 40 minutes and is dangerous. Tap water causes chlorine shock.

IssuesThe visit was decided, but the transport method had not been thought through in advance and a bucket was chosen in haste. The owner did not know the basics of fish transport (bagging, oxygen, insulation, darkness). There was no habit of recording the water-test data needed for the visit.

ImprovementAssemble a transport kit of thick bags, rubber bands, and a foam box, and practice the bagging procedure. Test and record the water weekly and bring the records to the visit. Make it a habit to photograph symptoms. Find a vet who treats fish in advance and phone before the visit to confirm the transport method.

1 a.m. In a 120 cm tank shared with the eel, the small fish are floating to the surface one after another and two are already dead. The eel is also gasping at the surface and tilting to one side. In the evening, new substrate was added and the filter was washed at the same time. A test kit shows high ammonia. The air pump is running. There is 60 L of aged water.

Which is the most appropriate first action?

1. Wait until morning and go to the vet when it opens
2. Remove only the dead fish and go back to bed
3. Take all the fish out and move them to a bucket of tap water
4. Remove the dead fish, do a 1/2 water change with aged water, turn aeration to maximum, phone an emergency (after-hours) vet who treats fish, and follow their instructions to come in if there is no improvement

AnswerD. Remove the dead fish, do a 1/2 water change with aged water, turn aeration to maximum, phone an emergency (after-hours) vet who treats fish, and follow their instructions to come in if there is no improvement

ExplanationSeveral fish gasping at once with deaths already occurring is a water-quality collapse such as ammonia poisoning, an emergency that can wipe out the tank within hours. The cause was washing the filter and replacing the substrate at the same time, which wiped out the filter bacteria at once. First remove the dead fish, do a 1/2 water change with aged water to dilute the ammonia, and turn aeration to maximum. Phone an emergency (after-hours) vet who treats fish, and if the eel's tilting does not improve, follow their instructions to come in. Waiting until morning means total loss. Removing the dead fish alone leaves the cause. Moving them to tap water adds chlorine poisoning.

IssuesThe filter was washed and the substrate completely replaced at the same time, without understanding the danger of losing the filter bacteria. The water was not tested after a major change, and the problem was not noticed until the middle of the night. No vet reachable at night had been identified.

ImprovementSpace filter cleaning and substrate changes at least 2 weeks apart, and always wash the filter in tank water. After a major change, test ammonia and nitrite a few hours later and the next morning. Keep aged water equal to half the tank volume on hand. Find a vet who treats fish and is reachable at night in advance, and post the contact details beside the tank.

A September morning. A family member has found the escaped eel half-dried on the floor. About half of its skin is dry and coated in grit, and its mouth moves faintly. Saying it is dirty, the family member is about to wash it under the tap. The tank is in the next room, and it takes a minute to fill a bucket with tank water. The air pump is running in the tank.

Which is the most appropriate first action?

1. Stop them, return it to a container of tank water with wet hands, rinse off the grit by pouring tank water over it, turn aeration to maximum, and wait for it to recover
2. Rinse the grit off under the tap, then return it to the tank
3. Blow the grit off with a hair dryer on the cool setting
4. Coat the dry body with salt to keep it moist

AnswerA. Stop them, return it to a container of tank water with wet hands, rinse off the grit by pouring tank water over it, turn aeration to maximum, and wait for it to recover

ExplanationAn eel can survive by skin breathing as long as it is moist, but half-dried it is near its limit. Even so, the chlorine and temperature difference of tap water are fatal to weakened gills and skin. Stop the family member, lift the eel with wet hands into a container of tank water, and rinse off the grit by pouring tank water over it. Turn aeration to maximum, hold it with the head forward so water flows through the gills, turn off the lights, and wait for recovery. If it swims on its own within 30 minutes to an hour, keep observing; if it stays on its side, see a vet the same day. A hair dryer dries it further. Salt damages the dry skin further and worsens dehydration.

IssuesEscape prevention was inadequate, and on top of that a family member nearly took the dangerous step of washing it in tap water. The basics of skin breathing and the harm of chlorine had not been shared with the family. No reserve of tank water was kept nearby for emergencies.

ImprovementPrevent escape with weights and netting on the lid. Make sure the whole family knows the rule for an eel found on the floor: never tap water; wet hands and into tank water; and post it on paper. Keep a bucket of reserved tank water or dechlorinated water on hand at all times. Decide the recovery benchmark and when to see a vet.