Ancient fish case method: 50 questions

A Polypterus senegalus (15 cm) bought from a shop last week was placed directly into the existing 90 cm tank. At feeding this morning, several white thread-like strands were seen waving on the dorsal fin and flank, and the fish is rubbing its body against the driftwood. The long-established Polypterus tankmate shows no change so far.

Which is the most appropriate first action?

1. Assume it is lint, remove it with tweezers, and watch
2. Isolate the newcomer in a separate tank, take photos, and see a vet the same day
3. Add the standard dose of an over-the-counter ich medication found online to the whole tank
4. Raise the water temperature to 32°C to weaken the parasites

AnswerB. Isolate the newcomer in a separate tank, take photos, and see a vet the same day

ExplanationWhite thread-like strands on the body plus rubbing are the classic signs of Macrogyrodactylus, a parasite specific to Polypterus. It reproduces fast and will spread to tankmates if left, so first isolate the newcomer, do not share equipment, and take photos to a vet who sees fish the same day. Removing with tweezers leaves eggs and larvae behind, so it recurs. Ich medication targets a different parasite and is unlikely to work, and self-prescribed medicated baths weaken the fish. A sudden rise to 32°C causes oxygen shortage and ill health and is dangerous for Polypterus.

IssuesThe biggest problem was putting the new fish straight into the main tank without quarantine observation in a treatment tank. The body surface was not checked at purchase, so a parasite was very likely brought in. There is now a risk of infecting the established fish too.

ImprovementAlways quarantine new fish in a separate tank for 2–4 weeks, checking the body and fins daily before moving them to the main tank. Keep separate nets and buckets for each tank. Make it a habit to check for white thread-like attachments on the body at the shop before buying.

A Protopterus (60 cm) kept for 3 years. On a summer evening, the owner came home to find it rising to the surface every 1–2 minutes instead of the usual once every 10 minutes or so. Foam has collected on the surface and there is a slightly fishy smell. A large amount of fish fillet was fed all at once yesterday, and leftovers are visible on the bottom. Water temperature is 29°C.

Which is the most appropriate first action?

1. Remove the leftover food, increase aeration, and do a 1/3 water change with temperature-matched water
2. Assume it is fine since the fish can breathe air and wait until tomorrow
3. Replace all the water and reset the tank
4. Add more food to build its strength

AnswerA. Remove the leftover food, increase aeration, and do a 1/3 water change with temperature-matched water

ExplanationA sudden increase in a lungfish's air breathing signals low dissolved oxygen or rising ammonia from leftover food. First remove the leftovers, increase aeration, and do a 1/3 change with temperature-matched new water to dilute the toxins. Test ammonia and nitrite with strips and see a vet the same day if there is no improvement. Even an air breather's gills and skin are damaged by ammonia, so leaving it is dangerous. A full water change loses the filter bacteria, and sudden pH and temperature swings weaken the fish further. Adding food accelerates water deterioration.

IssuesA large amount was fed during a hot period and the leftovers were not removed the same day. At 29°C, dissolved oxygen falls and water deteriorates faster, yet there was insufficient aeration and cooling. Knowing the fish's normal air-breathing rate was a good point.

ImprovementFeed adults 2–3 times a week, only what is eaten within a few minutes, and remove leftovers the same day. In summer, keep the water under 30°C with a cooling fan and run aeration at all times. Keep ammonia and nitrite test strips on hand so you can test immediately when something is off.

A datnoid (25 cm) in a 120 cm tank. During a water change 3 days ago, the owner forgot to match the temperature and the water dropped by 5°C. Today the edge of the tail fin is cloudy white and jagged as if dissolving, and the area around the mouth is whitish. It responds sluggishly to food and its color has darkened.

Which is the most appropriate first action?

1. Fins regrow, so increase feeding and wait for recovery
2. Add a large amount of salt for a strong salt bath
3. Move it to a quarantine tank, keep the temperature stable, and see a vet the same day
4. Cut off the dissolved parts with scissors and disinfect

AnswerC. Move it to a quarantine tank, keep the temperature stable, and see a vet the same day

ExplanationFins and mouth edges turning white and dissolving suggest columnaris. It progresses very fast and can kill within days, so move the fish to a quarantine tank, eliminate temperature swings, and see a vet the same day. More food will not cure it, and the darkened color shows severe stress. A strong salt bath done on your own judgment risks the wrong concentration and further exhausts a weakened fish. Cutting the fin only enlarges the wound and worsens infection; it is not treatment.

IssuesTemperature matching was skipped during the water change, and the sudden 5°C drop lowered immunity. Early signs of darkening and loss of appetite were missed for 3 days. A quarantine tank and heater may not have been prepared in advance either.

ImprovementAlways match new water to the main tank temperature before adding it. Datnoids show their condition through color, so record stripe intensity and appetite at each daily feeding. Keep a small quarantine tank, heater, and air pump ready so you can isolate immediately when something is wrong.

On a January morning, the owner noticed many fine white dots on the body and fins of a Polypterus delhezi (30 cm). The fish has clamped fins and is rubbing against the substrate. On checking, the heater's indicator light was off and the water temperature was 18°C. The heater was still plugged in, and yesterday's leftover food is lying in a corner of the tank.

Which is the most appropriate first action?

1. Install a spare heater, bring the temperature back to 26°C over several hours, then consult a vet
2. Raise it to 30°C at once to shed the white spots
3. Rub the white spots off with your fingers
4. Temperature is irrelevant, so just add medication

AnswerA. Install a spare heater, bring the temperature back to 26°C over several hours, then consult a vet

ExplanationA temperature drop from heater failure is a classic trigger for ich. First use a spare heater to bring the water back gradually to around 26°C over several hours. A sudden jump to 30°C causes oxygen shortage and strain that weaken the fish instead. The white spots are parasites embedded in the skin; rubbing will not remove them and damages the slime coat. Once the temperature is restored, it is safest to consult a vet who sees fish rather than medicating on your own. Heater failures recur, so check the cause at the same time.

IssuesOnly one heater was used in winter, so the failure was noticed late. Checking the thermometer was not a daily routine. Whether a spare heater was on hand decides how fast you can respond.

ImprovementSplit heating across two heaters so one failure does not cause a critical drop. Place the thermometer where it is easy to see and check it every morning. Have a spare heater and knowledge of ich treatment ready in advance, and follow water-change procedures that avoid temperature swings.

During a long summer business trip, the family looking after the lungfish (70 cm) did not top up the tank, and the water level dropped to 10 cm. On returning, the owner found the lungfish curled on the bottom, surrounded by a half-dried film of mucus, completely still. It responds slightly to touch.

Which is the most appropriate first action?

1. Conclude it is dead and remove it
2. Immediately fill the tank with cold tap water to wake it
3. Keep the cocoon moist so it does not dry out, do not force it awake, and see a vet within a few days to discuss how to wake it
4. Shake it hard to check for a response

AnswerC. Keep the cocoon moist so it does not dry out, do not force it awake, and see a vet within a few days to discuss how to wake it

ExplanationThe falling water level caused the lungfish to form a mucus cocoon and enter estivation. Its response to touch shows it is alive, but it will die if it dries out completely, so keep the cocoon moist. Suddenly pouring in a large amount of cold water is dangerous due to abrupt changes in temperature and osmotic pressure; waking must be done in stages, such as adding temperature-matched water little by little. It is safest to consult a vet about the waking procedure and a health check. Removing it as dead or shaking it imposes a fatal strain.

IssuesInstructions for topping up and maintaining water level during the long absence were inadequate, and the family was not told how important water level is for an air-breathing fish. Lack of knowledge about estivation also risked mistaking it for dead. No auto top-off or evaporation control was in place.

ImprovementDuring long absences, limit evaporation with an auto top-off or a sealed lid, and specify a minimum water level. Leave written instructions for the caretaker on how to check air-breathing frequency and water level. Keep water level and temperature stable on the principle of avoiding estivation in captivity.

A Polypterus endlicheri (50 cm) kept for 5 years. Water changes have been skipped for the past 2 weeks. Today the abdomen is swollen on both sides and the scales are standing out like a pinecone. There are red spots on the flank and it does not come when it sees food. Test strips show very high nitrate.

Which is the most appropriate first action?

1. Do a 1/3 water change with temperature-matched water, take photos, and see a vet the same day
2. Add salt and human antibiotics to the tank
3. Press the belly to squeeze out the fluid
4. Withhold food and watch for 2 weeks

AnswerA. Do a 1/3 water change with temperature-matched water, take photos, and see a vet the same day

ExplanationA swollen abdomen, raised scales, and hemorrhagic spots are classic Aeromonas infection on a background of poor water quality, and it becomes hard to save once advanced. First improve the water with a 1/3 change of temperature-matched water, then see a vet the same day with photos of the symptoms and water-quality data. Human antibiotics are the wrong type and dose and kill the filter bacteria, worsening the water. Pressing the belly damages the organs. Waiting 2 weeks means it will be too late.

IssuesWater changes were neglected for 2 weeks and nitrate accumulated. The early stage of reduced appetite and red spots was missed, letting it progress to severe pinecone condition. The root cause was not testing water quality regularly.

ImprovementFix a weekly 1/3 water change on the calendar and never skip the minimum even when busy. Test and log nitrate, ammonia, and nitrite twice a month. Observe the abdomen and scales at feeding time and set a rule to see a vet as soon as red spots appear.

A datnoid (20 cm) acquired last month. It ate frozen shrimp well last week, but for 2 days it has not eaten at all, turned jet black, and sits motionless in a corner of the tank. A same-sized Polypterus was recently added to the same tank. Water temperature 26°C; ammonia and nitrite are zero.

Which is the most appropriate first action?

1. Keep adding fresh food every day until it eats
2. Assume it is sick and give a medicated bath
3. Add hides and dim the lighting to reduce stress; see a vet if it continues 3 days or more
4. Shine strong light on it to bring back its color

AnswerC. Add hides and dim the lighting to reduce stress; see a vet if it continues 3 days or more

ExplanationWith normal water quality, darkening and food refusal right after adding a new tankmate is most likely a typical datnoid stress response. Add hides and dim the lighting to settle it, and always remove uneaten food. If it still does not eat for 3 days or more, or shows skin abnormalities or increased gill movement, see a vet within a few days. Continually adding uneaten food fouls the water. A medicated bath with no evidence of disease weakens the fish. Strong light increases a datnoid's stress.

IssuesA tankmate was introduced to a strongly territorial datnoid without a gradual process, and hides were lacking. The owner knew color change indicates stress but did not consider factors other than water quality.

ImprovementWhen adding a new fish, add hides first and acclimate with a divider before full cohabitation. Record a datnoid's stripe intensity daily and set a guideline for how many days of darkening is acceptable. Decide in advance the criteria for seeing a vet when food refusal continues (3+ days, or other symptoms appearing).

A lungfish (80 cm) kept for 8 years. Its begging was endearing, so it has been fed fatty fillets and beef heart every day. Lately its abdomen is always bloated, it stays still on the bottom, and breathes hard when it occasionally moves. Yesterday it lay limp at the surface and could not sink. The water is clean and no ammonia is detected.

Which is the most appropriate first action?

1. Reduce feeding and see a vet within a few days to discuss obesity and organ condition
2. Decide it is a swim bladder disease since it cannot sink, and leave it
3. Chase it with a net every day for exercise
4. Give large doses of vitamin supplements

AnswerA. Reduce feeding and see a vet within a few days to discuss obesity and organ condition

ExplanationA constantly swollen abdomen, labored movement, and floating after daily high-fat feeding strongly suggest organ damage from obesity or fatty liver. It can lead to sudden death, so cut back feeding, stop fatty foods, and see a vet within a few days for assessment. Abnormal buoyancy can be due to enlarged organs and worsens if left. Chasing with a net causes stress and injury, and lungfish may bite. Large vitamin doses have no basis and foul the water.

IssuesAn adult was fed high-fat food every day with no proper feeding schedule. The swollen belly was misread as a sign of a healthy appetite, and the owner was unaware of the risk of obesity despite 8 years of keeping.

ImprovementFeed adults 2–3 times a week, mainly low-fat pellets for carnivorous fish. Photograph body width and abdomen monthly to track obesity objectively. Share a household rule not to increase food in response to begging.

At 6 a.m., a Polypterus ornatipinnis (40 cm) was found on the living room floor. After last night's water change, the cable hole in the lid was left open. The skin is dry and rough, but the gill covers move slightly and the mouth opens from time to time. There is dust on the skin.

Which is the most appropriate first action?

1. Grab it right away with dry hands and toss it into the tank
2. Decide it cannot be saved and bury it
3. Lift it gently with wet hands or a wet cloth, return it to the tank, increase aeration, and see a vet the same day
4. Wash the body under tap water first, then return it

AnswerC. Lift it gently with wet hands or a wet cloth, return it to the tank, increase aeration, and see a vet the same day

ExplanationAn air-breathing Polypterus can recover even with dry skin if the gills or mouth are still moving. Lift it with wet hands or a wet cloth so as not to damage the slime coat and return it quietly to the tank. Increase aeration, turn off the lights, and see a vet the same day because of skin damage and risk of secondary infection. Grabbing with dry hands strips the slime coat, and tossing it in causes bruising. Never bury a fish that is alive. Chlorinated tap water damages the gills.

IssuesThe direct cause was leaving the cable hole open after the water change. Despite keeping a nocturnal fish that is active at night, checking the lid gaps was not part of the routine. The owner did not know how to handle a jumped fish and risked grabbing it with dry hands.

ImprovementAdd "seal lid gaps and cable holes" to the post-water-change checklist and confirm by pointing. Keep the water level at least 5 cm below the lid. Post a wet towel and the vet's contact next to the tank for jump emergencies. Lay a thick mat on the floor so you can hear a fall.

While feeding, the owner held a fillet with their fingers in front of a lungfish (90 cm) and was bitten, finger and all. The tooth plates have sunk in and the lungfish hangs on without letting go. The pain is intense and the owner is about to yank their arm back reflexively. A family member is beside them. The tank is 180 cm and the lungfish's mouth is just below the surface.

Which is the most appropriate first action?

1. Pull free with all your strength and get away
2. Stay still and relax, keep the fish's head underwater while waiting for it to let go, and run water against the side of its mouth
3. Lift the fish out of the tank and put it on the floor
4. Have the family member hit the fish on the head

AnswerB. Stay still and relax, keep the fish's head underwater while waiting for it to let go, and run water against the side of its mouth

ExplanationA lungfish's tooth plates are strong, and pulling free tears skin and tendons, enlarging the wound. Stay still and relax, keep the fish's head underwater while waiting for it to release on its own, and if it does not, run water against the side of its mouth to stimulate it. Taking the fish out of the tank makes it thrash and bite deeper, and injures the fish too. Hitting the head harms the fish and can make it bite even harder. Once released, rinse the wound under running water and, if deep, see a doctor and tell them a fish bit you.

IssuesFeeding was done directly by hand, with no caution about the lungfish's bite force and the position of its mouth. The owner did not know the procedure for a bite and risked yanking free reflexively. No tongs or feeding stick had been prepared.

ImprovementAlways feed lungfish with long tongs or chopsticks and keep fingers away from the surface. Always check where the lungfish's mouth is during tank work and tell family members before putting your hands in. Write the bite procedure (stay still, wait underwater, rinse under running water, see a doctor) on paper and post it beside the tank.

A lungfish (60 cm) and a Polypterus (45 cm) are kept together in a 180 cm tank. There was violent splashing in the night, and in the morning the Polypterus has a large bite mark on its flank with several scales torn off and flesh exposed. The lungfish is chasing the Polypterus.

Which is the most appropriate first action?

1. Isolate the bitten Polypterus, photograph the wound, and see a vet the same day
2. Wait and see until they get along
3. Apply antiseptic directly to the wound
4. Withhold food to punish the lungfish

AnswerA. Isolate the bitten Polypterus, photograph the wound, and see a vet the same day

ExplanationLungfish are aggressive and relentlessly attack tankmates. A deep bite with scales torn off and flesh exposed is an entry point for bacterial infection, and if the chasing continues it will be bitten again. First move the bitten fish to a quarantine tank, photograph the wound, and see a vet the same day. Keeping the quarantine water clean is the basis of recovery. Waiting invites further bites and infection. Applying antiseptic directly to a fish damages the slime coat and leaches into the water, harming the gills. Withholding food does not curb aggression.

IssuesThe basic rule that lungfish are kept alone was ignored. The nighttime attack went unnoticed and no divider had been prepared. Without a quarantine tank ready, the initial response risked being delayed.

ImprovementReturn the lungfish to solitary keeping. If the same tank must be used, separate completely with a sturdy divider so no contact is possible even at night. Keep a quarantine tank and heater on hand and share the bite response with the family. Record the Polypterus's wound daily with photos.

At night, the moment the room light was switched on suddenly, a datnoid (30 cm) was startled and rammed hard into the glass. The tip of the snout is scraped red with a little blood seeping. It has since gone dark and sits still in a corner. Water temperature is 26°C with no water-quality problems, and there are no tankmates.

Which is the most appropriate first action?

1. Take the fish out and put a bandage on the wound
2. Dim the lights to keep it calm, keep the water clean with changes, and see a vet the same day if white fungus or dissolving appears
3. Feed extra every day until the wound heals
4. Drop the water temperature sharply to stop the bleeding

AnswerB. Dim the lights to keep it calm, keep the water clean with changes, and see a vet the same day if white fungus or dissolving appears

ExplanationPressure cannot be applied to a fish's abrasion, so first dim the lights to avoid startling it, keep it quiet, and maintain clean water to prevent secondary infection. A minor snout abrasion usually heals on its own with good water, but if the wound grows white fungus or spreads as if dissolving, that is columnaris or water mold, so see a vet the same day. Taking the fish out to bandage it is counterproductive due to drying and slime-coat damage. Extra food fouls the water. A sudden temperature drop lowers immunity and invites infection.

IssuesThe light was switched on suddenly in a room with a nocturnal, timid fish, startling it. The tank layout and a dim environment may have been lacking. Without knowing the criteria for monitoring the wound, an infection could be missed.

ImprovementBrighten the room lighting gradually and turn on the tank light after the room light. Add smooth driftwood and hides to give the fish an escape when startled. Photograph the wound daily and set a rule to see a vet if it turns cloudy white or enlarges.

A Polypterus palmas (25 cm) always rested on an unguarded heater placed directly on the bottom. This morning there is a band of red discoloration from the belly up the flank, with part of it white and raw. The fish is breathing air as usual. Water temperature is a stable 25°C and it has an appetite.

Which is the most appropriate first action?

1. Remove the heater and lower the temperature; it will heal, so leave it
2. Apply ice to the raw area to cool it
3. Fit a guard on the heater and mount it off the bottom, photograph the area, and see a vet the same day if it is extensive
4. Rub the area to peel off the skin

AnswerC. Fit a guard on the heater and mount it off the bottom, photograph the area, and see a vet the same day if it is extensive

ExplanationPolypterus habitually rest on the bottom and can be burned by prolonged contact with an unguarded heater. A band of red discoloration with raw patches is a typical heater burn. First prevent recurrence by fitting a guard and mounting the heater off the bottom, then photograph the area. Extensive raw patches are prone to infection and need a vet the same day. Removing the heater drops the temperature, lowering immunity and inviting ich. Ice or peeling the skin damages the tissue further. Keeping the water clean is the basis of recovery.

IssuesThe heater was placed directly on the bottom without a guard, and nothing was done even though the owner knew the fish rested on it. The bottom-dwelling habit was not connected to the risk of burns.

ImprovementAlways use a heater guard and fix the heater off the bottom in a spot with water flow. Observe where the fish rests and check weekly that it is not touching dangerous equipment. Record the burn daily with photos and see a vet if the white raw area spreads.

During a power outage in the night, while walking to find a flashlight, the owner stepped on something slimy on the floor. With the lights on, it turned out to be a Polypterus (35 cm) that had jumped. The middle of its body is dented and bent, with a little blood from the mouth. The gills are moving. The room was pitch dark and the cable hole in the tank lid had been left open.

Which is the most appropriate first action?

1. Return it to the tank with wet hands, secure aeration, and contact an emergency (after-hours) animal hospital
2. Apply a splint since a fracture is suspected
3. Leave it on the floor until morning and watch
4. Stretch the body out to straighten it

AnswerA. Return it to the tank with wet hands, secure aeration, and contact an emergency (after-hours) animal hospital

ExplanationBody deformation from being stepped on, plus bleeding from the mouth, strongly suggests internal or spinal injury. A fish cannot be treated out of water, so return it gently to the tank with wet hands, secure oxygen with a battery-powered air pump even during the outage, and contact an emergency (after-hours) animal hospital. Splints cannot be used on fish, and stretching the body worsens the damage. Left on the floor it dies of drying and suffocation. Bleeding or deformation calls for a vet right now, not later the same day.

IssuesThe owner had not anticipated that jumps are likely during a blackout, and no place was set for a flashlight. The lid weighting and gap sealing were inadequate, and no battery-powered air pump was prepared for outages.

ImprovementKeep flashlights in fixed spots beside the tank and in the bedroom, and during an outage light your feet before walking. Weight the lid and seal the cable hole with sponge. Keep a battery-powered air pump on hand and post the emergency (after-hours) animal hospital's contact beside the tank.

No sponge was fitted on the canister filter intake. On coming home, a juvenile Polypterus senegalus (12 cm) had its tail fin sucked into the intake and is twisting violently, unable to get free. The tail fin is starting to tear. The tank is 60 cm and there are no other fish.

Which is the most appropriate first action?

1. Pull on the fish's body to free it
2. Switch off the filter to stop the suction, wait for the fish to free itself, then check the injury
3. Leave it; it will come free on its own
4. Lift the whole intake out of the tank

AnswerB. Switch off the filter to stop the suction, wait for the fish to free itself, then check the injury

ExplanationPulling a sucked-in fish tears the fin and injures the body. Switching off the filter stops the suction and the fish usually frees itself. Once free, check how badly the tail is torn, take photos, and keep the water clean. See a vet if the tear is large, bleeding continues, or white fungus appears within a few days. Left alone, the fish weakens and dies from the suction. Lifting the intake out makes the fish thrash in the air and injures it further. Fit a sponge on the intake to prevent recurrence.

IssuesA juvenile was kept without a protective sponge on the intake, overlooking the danger of strong suction. There was insufficient consideration that smaller fish are more easily sucked in.

ImprovementAlways fit a sponge or mesh on the intake, choosing a mesh size suited to the juvenile's size. Place the filter's power switch within reach so it can be stopped immediately in an emergency. Check at feeding time that no fish is near the intake.

The family cat jumped onto the light plastic lid of a 90 cm tank and fell in, lid and all. The cat leapt out at once, but the Polypterus delhezi (30 cm) is panicking, swimming wildly around the tank and hitting the glass. Cat hair floats on the surface and the lid is underwater, bumping the fish.

Which is the most appropriate first action?

1. Do nothing and watch until the fish settles
2. Remove the lid from the tank, turn off the lights, move the cat to another room, and check the fish's skin for injuries
3. Catch the fish with a net right away and move it to another tank
4. Replace all the water to remove the cat hair

AnswerB. Remove the lid from the tank, turn off the lights, move the cat to another room, and check the fish's skin for injuries

ExplanationFirst quietly remove the lid from the water to stop it hitting the fish, turn off the lights to calm it, and move the cat to another room to prevent further contact. Once the fish settles, check the skin for wounds or abrasions; photograph any and monitor. Chasing a panicked fish with a net makes it ram the glass more and worsens injuries. A full water change loses the filter bacteria and destabilizes the water. Scooping the hair with a net is enough. Scratches from cat claws are prone to infection, so see a vet if a wound turns cloudy white.

IssuesA light plastic lid was used in a home with a cat, leaving it climbable. Furniture near the tank gave the cat a foothold. Safety measures for both the cat and the fish were lacking.

ImprovementUse a heavy glass or acrylic lid and add weights on top. Do not place furniture near the tank that a cat can use as a foothold. Set the tank up in a room the cat cannot enter, or fit a guard rail on the stand. Cat claws damage the fish's slime coat, so observe for several days after any contact.

While draining the tank with the lid off for a water change, the phone rang and the owner stepped away for about 5 minutes. On returning, the Polypterus endlicheri (45 cm) was not in the tank. A trail of water drops on the floor leads behind the tank stand. The lid is still off and the water level is 15 cm lower than usual.

Which is the most appropriate first action?

1. Follow the water trail to search behind the stand and under furniture, and return it with wet hands when found
2. Wait for it to come back on its own
3. Assume the fish is dead and continue the water change
4. Probe under the furniture with a vacuum cleaner

AnswerA. Follow the water trail to search behind the stand and under furniture, and return it with wet hands when found

ExplanationPolypterus readily jump when the lid is off, and after landing on the floor they crawl toward dark places. Follow the water trail, shine a light behind the stand and under furniture, and when found, lift it with wet hands or a wet cloth and return it to the tank. Even if dry, it may recover if still breathing, so see a vet the same day. It will never return to the tank on its own, and the longer it takes, the lower the survival rate due to drying. A vacuum cleaner injures the fish. Suspend the water change until it is found.

IssuesThe owner left the tank with the lid off. Even knowing that air-breathing fish are especially prone to jumping when the level drops and there is no lid, this was not built into the procedure.

ImprovementNever leave a tank with the lid off during a water change. If you must step away, place a temporary lid (a board or net). Finish phone calls before the water change or let them go to voicemail. Reduce gaps behind and around the stand so a fallen fish is easy to find.

In a tank with coarse gravel, a Polypterus ornatipinnis (35 cm) was seen several times swallowing gravel along with sinking food. Today it cannot spit the gravel out, its mouth is stuck open, and its belly is unnaturally swollen. It does not respond to food.

Which is the most appropriate first action?

1. Put a finger in its mouth and pull the gravel out
2. Take the fish out of the water and press its belly
3. Feed more to encourage it to pass
4. Stop feeding, photograph the mouth and belly, and see a vet the same day

AnswerD. Stop feeding, photograph the mouth and belly, and see a vet the same day

ExplanationCoarse gravel can lodge in the mouth or digestive tract; a swollen belly and a mouth that will not close suggest an obstruction. Since it cannot clear it on its own, stop feeding, take photos, and see a vet the same day to discuss treatment. A finger in the mouth injures it, and a Polypterus's mouth is small, so forcing it open damages the jaw. Pressing the belly causes organ damage. More food will not clear the blockage and makes it worse. To prevent recurrence, switch to fine sand or a bare-bottom tank.

IssuesGravel small enough to fit in the mouth was used for a fish that forages along the bottom. The owner saw it swallowing gravel several times and did nothing. The choice of substrate did not suit the fish's habits.

ImprovementUse a bare-bottom tank or a thin layer of fine, smooth sand. Feed with a feeding dish or tongs so food is not sucked in with gravel. Make it a rule to see a vet the same day, not the next, when the mouth or belly looks abnormal.

On a summer night, a large amount of mosquito spray was used in the room with the tank. 30 minutes later, the lungfish (60 cm), which takes in air through the gap in the lid, is thrashing violently at the surface, swimming with its body twisted, and trembling as if in spasm each time it breathes. Fish in other rooms are unaffected.

Which is the most appropriate first action?

1. Open the windows to ventilate, do a large water change with temperature-matched water plus aeration, and consult an emergency (after-hours) animal hospital
2. Seal the lid tightly and wait for the fish to settle
3. Darken the room to avoid stimulation and watch until morning
4. Add a large amount of salt to neutralize the insecticide

AnswerA. Open the windows to ventilate, do a large water change with temperature-matched water plus aeration, and consult an emergency (after-hours) animal hospital

ExplanationInsecticide ingredients are highly toxic to fish, and air-breathing lungfish are hit especially hard because they inhale the contaminated air at the surface directly. First ventilate to clear the airborne chemicals, then do a large water change with temperature-matched water to dilute what has settled on the surface, and run activated carbon filtration and aeration. Neurological signs are present, so consult an emergency (after-hours) animal hospital. Sealing the lid traps the contaminated air. Waiting until morning is fatal. Salt has no neutralizing effect and the osmotic change weakens the fish further.

IssuesInsecticide was sprayed in the room with the tank. The owner did not realize that air-breathing fish are directly affected by the quality of air at the surface. No thought was given to chemicals entering through the gap in the lid.

ImprovementDo not use insecticides, air fresheners, or foggers in the room with the tank. If unavoidable, move the fish to another room or cover the tank with cloth and ventilate thoroughly afterward. Keep activated carbon on hand so it can be added immediately in case of chemical contamination. Make sure the family knows chemicals are banned in that room.

Right after applying ointment for chapped hands and rubbing alcohol, the owner rearranged the tank decor with bare hands. An hour later, the datnoid (25 cm) is tilting onto its side near the surface and moving its gills rapidly. An oily film floats on the surface. Water temperature is 25°C, and appetite and color were normal until yesterday.

Which is the most appropriate first action?

1. Removing the oily film with a tissue is enough
2. Do a 1/3–1/2 water change with temperature-matched water, add activated carbon and aeration, and see a vet the same day if no improvement
3. Take the fish out and put it in a bucket of tap water
4. Add a little detergent to break up the film

AnswerB. Do a 1/3–1/2 water change with temperature-matched water, add activated carbon and aeration, and see a vet the same day if no improvement

ExplanationChemicals on the hands such as ointment, alcohol, or detergent dissolve into the water and damage the gills. Tilting over and rapid gill movement are signs of poisoning and oxygen shortage, so first do a 1/3–1/2 change with temperature-matched water to lower the concentration, adsorb with activated carbon, and increase aeration. See a vet the same day if there is no improvement. Removing the film alone leaves the dissolved chemicals. Untreated chlorinated tap water damages the gills further. Detergent is highly toxic and fatal.

IssuesTank work was done bare-handed right after applying medication. There was little awareness that hand cleanliness directly affects water quality. No emergency adsorbent such as activated carbon was on hand.

ImprovementWash hands with soap and rinse well before tank work. Do not work right after applying medication or cosmetics, or use clean disposable gloves. Keep activated carbon and pre-conditioned water on hand and set a procedure for chemical contamination.

In August, the owner went out with the air conditioner off and came home in the evening to find the thermometer reading 33°C. The Polypterus endlicheri (50 cm) is near the surface with its mouth open, gulping air repeatedly, fins clamped. The datnoid is starting to tilt over on the bottom. Aeration was weak and the lights had been left on.

Which is the most appropriate first action?

1. Put ice directly in the tank to cool it fast
2. Turn on the air conditioner and cooling fan, set aeration to maximum, and do small changes with slightly cooler water to lower the temperature 1–2°C at a time
3. Leave the lights on and watch until morning
4. Move the fish to a bucket of cold tap water

AnswerB. Turn on the air conditioner and cooling fan, set aeration to maximum, and do small changes with slightly cooler water to lower the temperature 1–2°C at a time

Explanation33°C is dangerous even for ancient fish; dissolved oxygen falls, causing increased air gulping and tilting over. First lower room and water temperature with the air conditioner and a cooling fan, and set aeration to maximum to add oxygen. Do water changes gradually with water slightly cooler than the tank, dropping 1–2°C at a time. Ice placed directly causes local rapid cooling and ill health. A bucket of cold tap water is fatal from the temperature difference and chlorine. Lights raise the temperature, so turn them off. Consider a same-day vet visit for a fish lying on its side.

IssuesThe owner went out in midsummer with the air conditioner off and no preparation for rising temperature. No cooling fan or thermostat-linked cooling equipment was installed, and there was no procedure for high temperatures.

ImprovementIn summer, run the air conditioner continuously or link a tank chiller or cooling fan to a thermostat to stay under 30°C. Use a thermometer app that lets you check the water temperature while out. Keep pre-conditioned water and a battery-powered air pump for emergencies.

On a January night, heavy snow caused a blackout with no prospect of restoration. The 180 cm tank has dropped from 26°C to 22°C in 3 hours, and room temperature is 8°C. The lungfish (80 cm) is motionless on the bottom and the Polypterus's air breaths are getting further apart. The filter has stopped too. A flashlight, blankets, and a battery-powered air pump are at hand.

Which is the most appropriate first action?

1. Cover the tank with blankets or foam, run the battery air pump, and float hot-water bottles or warmed plastic bottles in the tank to retain heat gradually
2. Pour hot water straight in to bring it back to 26°C at once
3. Take the fish out and move them to warm water in the bathtub
4. Do nothing and simply wait for power to return

AnswerA. Cover the tank with blankets or foam, run the battery air pump, and float hot-water bottles or warmed plastic bottles in the tank to retain heat gradually

ExplanationIn a blackout, first cover the tank with blankets or foam to limit heat loss and secure oxygen with a battery-powered air pump. Floating hot-water bottles or warmed plastic bottles provides gentle warmth. Pouring hot water in directly causes local overheating and sudden change. The bathtub is dangerous due to chlorine, detergent residue, and the temperature difference. Doing nothing lets it fall below 18°C, bringing ich and indigestion, and ammonia rises with the filter stopped. Stop feeding during the outage; restart the filter and check water quality once power returns.

IssuesThere was no preparation for retaining heat and securing oxygen in a winter blackout. Large tanks cool slowly but also take time to warm back up. Stocks of battery air pumps and insulation were lacking.

ImprovementKeep a battery-powered air pump with spare batteries, foam boards, and blankets near the tank. If you have a portable power station, check it has the capacity to run one heater. Write down the three blackout basics (stop feeding, insulate, oxygen) and share them with the family.

An owner kept cleaning the tank bare-handed with a cut on one finger. 3 weeks later, a hard reddish-purple lump formed on the finger where the cut was, and a chain of small lumps now runs up toward the wrist. There is little pain but it is not healing. The Polypterus being kept shows no abnormality.

Which is the most appropriate first action?

1. Apply an over-the-counter ointment and watch
2. Give up all the fish since they are the source of infection
3. See a dermatologist and mention the possible infection through a cut during fish keeping
4. Lance the lump with a needle to drain the pus

AnswerC. See a dermatologist and mention the possible infection through a cut during fish keeping

ExplanationAtypical mycobacteriosis, caught through cuts exposed to tank water or fish, typically shows a reddish-purple lump after several weeks that spreads in a chain along the lymphatics. Ordinary ointments will not cure it and it needs proper diagnosis and treatment, so see a dermatologist and mention the possible infection through a cut during tank work. Lancing with a needle spreads the infection. There is no need to give up the fish; basic measures like keeping hands out of the tank when cut and washing after work prevent it. Even with no symptoms in the fish, the bacteria can be present in the water.

IssuesTank work continued bare-handed with a cut on the hand. The owner had no knowledge of zoonoses from fish and left a non-healing lump untreated. Wearing gloves and washing hands after work were not habits.

ImprovementDo not put your hands in the tank when they are cut; use long disposable gloves if necessary. Wash hands with soap after work. See a dermatologist early for any lump or swelling that will not heal and always mention that you keep fish.

During a water change, a 3-year-old scooped old tank water from the bucket with their hands and put it in their mouth, then ate snacks with the same hands. The water is slightly cloudy and smells fishy. It is from the lungfish tank and contains dirt from the substrate. The child seems fine so far and has gone on playing without washing their hands.

Which is the most appropriate first action?

1. Have the child rinse their mouth and wash their hands with soap, watch for diarrhea or fever for a few days, and if symptoms appear see a pediatrician and mention the tank water
2. Put a finger down the throat to make them vomit right away
3. Do nothing since the child seems fine
4. Throw out the fish and get rid of the tank

AnswerA. Have the child rinse their mouth and wash their hands with soap, watch for diarrhea or fever for a few days, and if symptoms appear see a pediatrician and mention the tank water

ExplanationTank water and substrate can harbor bacteria such as Salmonella that infect humans, so first have the child rinse their mouth and wash their hands with soap. Watch for diarrhea, fever, and abdominal pain for a few days, and if symptoms appear, see a pediatrician and mention that the child drank fish tank water. Forcing vomiting risks aspiration and is unnecessary for a small amount of water. Doing nothing risks missing symptoms. Removing the tank is excessive; the basic step of keeping water out of a child's reach during work prevents this.

IssuesDirty tank water was left within a child's reach during the water change. Awareness that tank water can be a source of infection was low, and the setup did not anticipate a small child's behavior.

ImprovementHave someone watch the child in another room during water changes, or cover the bucket and place it up high. Do not pour tank water down the kitchen sink, and have the whole family wash their hands thoroughly after work. Teach the child a rule not to touch tank water or equipment.

At 9 p.m., a Polypterus endlicheri (55 cm) is floating on its side at the surface with only the gills moving slowly. It tries to right itself but immediately falls over again. It was swimming normally this morning. All the filter media was washed yesterday and the water has been cloudy white since.

Which is the most appropriate first action?

1. It is swim bladder disease, so fast it and wait a week
2. Set aeration to maximum, do a water change with temperature-matched water, and contact an emergency (after-hours) animal hospital
3. Push the fish down by hand and hold it on the bottom
4. Since it is at the surface, feed it to build strength

AnswerB. Set aeration to maximum, do a water change with temperature-matched water, and contact an emergency (after-hours) animal hospital

ExplanationFloating on its side with only the gills moving is critical. Washing all the filter media destroyed the filter bacteria, so poisoning from a sharp rise in ammonia or nitrite is strongly suspected. First set aeration to maximum to secure oxygen, do a water change with temperature-matched water to dilute the toxins, and contact an emergency (after-hours) animal hospital. Assuming swim bladder disease and leaving it can mean death within hours. Holding it down does nothing if the water is not improved and worsens stress. Food fouls the water further.

IssuesAll the filter media was washed at once, destroying the filter bacteria. The cloudy white water, a sign of water-quality collapse, was missed and no water test was done. The owner lacked the perspective of suspecting water quality first rather than labeling a critical symptom with a disease name.

ImprovementNever wash all the media at once; rinse half at a time lightly in tank water. If the water turns cloudy, test ammonia and nitrite immediately and respond with water changes. Prepare the emergency (after-hours) animal hospital's contact, a transport bag, and a styrofoam box, and share with the family that lying on its side is a see-the-vet-now sign.

Quarantine of the newcomer was delayed, and a week later white thread-like parasites were found on the fins of both established fish, a Polypterus endlicheri (50 cm) and a P. delhezi (30 cm). All three are rubbing and their fin edges are ragged. The same net and bucket are shared across three tanks. The vet is not open until tomorrow morning.

Which is the most appropriate response for tonight?

1. Assign separate nets and buckets to each tank, stop carrying anything to other tanks, maintain water quality with changes, and see a vet first thing tomorrow
2. Add the same medication to every tank to wipe them out at once
3. Raise the water temperature to 34°C until the parasites drop off
4. Cut off the fins to remove the parasites with them

AnswerA. Assign separate nets and buckets to each tank, stop carrying anything to other tanks, maintain water quality with changes, and see a vet first thing tomorrow

ExplanationMacrogyrodactylus spreads between tanks via equipment. The best you can do tonight is stop sharing equipment to prevent further spread, maintain water quality with temperature-matched changes to keep the fish strong, and see a vet first thing in the morning with photos and water-quality data. The type and dose of medication depend on the parasite and the fish's condition; self-prescribed dosing of every tank weakens the fish and can crash the filter. 34°C is a dangerously high temperature for Polypterus. Cutting fins invites infection through the wounds.

IssuesNets and buckets were shared across multiple tanks, spreading the parasite. The delayed quarantine of the first fish also caused the spread. The owner had no emergency (after-hours) animal hospital to consult, delaying the start of treatment.

ImprovementColor-code nets, buckets, and hoses and dedicate them to each tank. Always quarantine new arrivals, and if a parasite is found on even one fish, put every fish in that tank under observation. Identify in advance a vet who sees fish and an after-hours contact.

A lungfish (90 cm) kept for 10 years. Water changes were cut back to once a month starting last month. This morning the right eye is cloudy white and bulging, with redness around the rim. It eats, but has been bumping into the side walls more often. Fine bubbles linger on the surface and nitrate is high.

Which is the most appropriate first action?

1. The eye is only a cosmetic problem, so leave it
2. Put human eye drops directly into the fish's eye
3. Do a 1/3 water change with temperature-matched water, photograph the eye, and see a vet within a few days
4. Take the fish out of the water to push the eye back in

AnswerC. Do a 1/3 water change with temperature-matched water, photograph the eye, and see a vet within a few days

ExplanationA bulging, cloudy eye is a classic sign of bacterial infection such as Aeromonas on a background of poor water quality, consistent with the high nitrate from insufficient water changes. First improve the water with a 1/3 change of temperature-matched water, then see a vet within a few days with photos of the eye and water-quality data. Acting while it still has an appetite matters. Left untreated, it can progress to blindness or systemic infection. Human eye drops cannot be used on fish and foul the water. Taking it out and pressing the eye damages the eyeball and slime coat.

IssuesWater changes on a large fish's tank were cut to once a month and nitrate built up. The lingering bubbles, a sign of deteriorating water, were missed. Complacency from long experience led to neglect of water testing.

ImprovementLarge fish produce a lot of waste, so strictly keep to a weekly 1/3 water change. Learn to read lingering surface foam and odor as signs of poor water and change water immediately. Record eye and skin abnormalities with photos and treat redness or bulging as a criterion for seeing a vet.

In November, a datnoid (28 cm) is rubbing repeatedly against the driftwood with clamped fins. On closer inspection there are a dozen or so white dots on the pectoral fins and flank. A large water change was done a week ago without temperature matching. Current water temperature is 24°C and the heater is working normally.

Which is the most appropriate first action?

1. Wash the fish, leaving only the parts without spots
2. Stop temperature swings, dim the lights to keep it calm, take photos, and consult a vet about medication
3. If it seems fine, leave it for a few weeks to heal on its own
4. Replace all the water to flush out the parasites

AnswerB. Stop temperature swings, dim the lights to keep it calm, take photos, and consult a vet about medication

ExplanationWhite dots plus rubbing are classic ich, triggered by sudden changes such as a water change without temperature matching. First stabilize the temperature, dim the lights to keep it calm, take photos, and consult a vet who sees fish about medication and temperature management. Washing the body damages the slime coat, and the spots are embedded so they will not come off. Left alone, the spots multiply and spread to the gills, causing death from respiratory failure. A full water change crashes the filter, removes only part of the parasites in the water, and stresses the fish with sudden change.

IssuesTemperature matching was skipped during the water change, subjecting the fish to a sudden swing. There was little awareness that ich is common from autumn into winter. The early rubbing behavior was not immediately recognized as abnormal.

ImprovementAlways match new water to within 1°C of the main tank. In autumn and winter, check the thermometer daily and review heater settings. Learn that rubbing is a sign of parasites or poor water, and inspect the body the same day you notice it.

On a winter night, a Polypterus senegalus (30 cm) sits motionless on the bottom and has not taken an air breath for over 30 minutes, versus the usual every 5 minutes. The gill covers are moving slowly. The thermometer reads 26°C, but the end of the tank feels cold to the touch. The heater light keeps flicking on and off.

Which is the most appropriate first action?

1. Fewer air breaths means it is relaxed, so there is nothing to worry about
2. Shake the fish to make it breathe
3. Measure the bottom and end temperatures with a separate thermometer; if the heater has failed, swap in a spare and warm up gradually, and see a vet the same day if no improvement
4. Drop food in front of it to see if it moves

AnswerC. Measure the bottom and end temperatures with a separate thermometer; if the heater has failed, swap in a spare and warm up gradually, and see a vet the same day if no improvement

ExplanationGreatly lengthened intervals between air breaths and lying motionless on the bottom signal a slowed metabolism from low temperature or weakness. If the thermometer measures only one part of the tank, there may be uneven temperatures, so check the bottom and the end with a separate thermometer. If the heater has failed, swap in a spare and warm up over several hours; if activity does not return, see a vet the same day. Never mistake fewer air breaths for reassurance. Shaking or feeding strains a hypothermic fish.

IssuesOnly one thermometer was installed, so the heater malfunction was not detected. Abnormalities in the direction of fewer air breaths are easy to miss; knowing the normal interval was the one saving grace. Whether a spare heater is on hand decides the response.

ImprovementInstall thermometers at two spots away from the heater and compare them daily. Split heating across two heaters so a single failure does not drop the temperature. Tell the family that air breathing can go abnormally down as well as up, and record the normal interval.

When fed a fillet with metal tongs, the datnoid (22 cm) lunged and the tip of the tongs struck the inside of its mouth. A little blood seeps from the corner of the mouth; it spat out the food and moved to a corner of the tank. Water quality is good and temperature is 26°C. There are no tankmates and it is fed 3 times a week.

Which is the most appropriate first action?

1. Catch the fish and open its mouth to check inside
2. Lower the water temperature to stop the bleeding
3. Offer food again right away to check its appetite
4. Stop feeding, dim the lights, record the mouth wound with photos for a few days, and see a vet if it turns white and starts dissolving

AnswerD. Stop feeding, dim the lights, record the mouth wound with photos for a few days, and see a vet if it turns white and starts dissolving

ExplanationA small mouth wound from a feeding tool usually heals on its own if the water is good. Stop feeding, dim the lights, keep it quiet, and photograph the wound for several days. If it turns cloudy white, spreads as if dissolving, or the mouth will not close, that is an infection such as columnaris, so see a vet the same day. Catching the fish and opening its mouth damages the jaw. Lowering the temperature does not stop bleeding and reduces immunity. Pushing food into an injured mouth enlarges the wound. Switch to a plastic feeding tool with a rounded tip.

IssuesSharp-tipped metal tongs were used on a fish that lunges at food, injuring the mouth. The tool was not chosen with the fish's speed at feeding in mind. The criteria for monitoring the wound were also vague.

ImprovementFeed with a rounded-tip plastic feeding stick or tongs, and release the food in front of the fish so it eats on its own. Feed in the same spot each time so the fish's movements are predictable. Record mouth wounds with photos and see a vet if they turn cloudy or enlarge.

For a move, a lungfish (70 cm) was bagged and driven for 2 hours. On arrival, the single-layer bag was nearly bitten through from the inside, several scales on the flank are torn off with abrasions, and mucus is abnormally heavy. The mouth stays open and it is breathing hard. The car was heated, but the bag was placed on the seat without a box.

Which is the most appropriate first action?

1. Match the bag water to the new tank temperature, transfer it quietly, increase aeration, photograph the wounds, and see a vet the same day
2. Put it in a strong salt bath for several hours to disinfect the wounds
3. Feed it right away to calm it down
4. Drop it straight into the new tank, skipping temperature matching

AnswerA. Match the bag water to the new tank temperature, transfer it quietly, increase aeration, photograph the wounds, and see a vet the same day

ExplanationThrashing and biting during transport tore off scales; heavy mucus and labored breathing indicate stress and skin damage. First match the bag water to the new tank temperature, acclimate, then transfer quietly, increase aeration, and dim the lights. Photograph the wounds and see a vet the same day to discuss infection control. A prolonged strong salt bath is a heavy burden on a weakened fish and dangerous without professional guidance. Feeding right after transport causes indigestion. Skipping temperature matching weakens it further with sudden change.

IssuesA single-layer bag was used without considering a lungfish's bite, and too much water made thrashing easy. Insulation and darkness were likely inadequate during the 2-hour trip. No vet or specialist shop was consulted about transport methods beforehand.

ImprovementTransport lungfish in at least a double bag with only enough water to cover the body, plenty of air, and in a dark, insulated styrofoam box. For long distances, consult a specialist transporter or a vet who sees fish. Decide in advance the acclimation procedure and quarantine observation period after arrival.

A Polypterus ornatipinnis (40 cm) that jumped 3 days ago was returned to the tank. It could swim at first, but today the dried parts of the skin are peeling white with red, swollen edges. The mucus is stringy and the air-breathing rate has increased. Ammonia reads zero.

Which is the most appropriate first action?

1. Remove all the peeling skin with tweezers
2. Take it out of the water to dry the affected area
3. Keep the water clean with temperature-matched changes, photograph the area, and see a vet the same day
4. It has recovered, so keep feeding as usual and watch

AnswerC. Keep the water clean with temperature-matched changes, photograph the area, and see a vet the same day

ExplanationSkin that dried out after a jump dies and peels a few days later, and bacteria or water mold easily infect it. Red swelling, stringy mucus, and increased air breathing are signs of secondary infection and weakening, so keep the water clean with temperature-matched changes and see a vet the same day to discuss treatment. Forcibly removing peeling skin damages healthy tissue too. Drying the area is fatal for a fish. Assuming recovery and leaving it lets the infection spread through the body. Daily observation for at least a week is needed after a jump.

IssuesReassured that it could swim right after the jump, the owner skipped the vet. The owner did not know that dried skin dies and becomes infected a few days later. No observation period or vet criteria had been set for after a jump.

ImprovementAfter a jump, see a vet the same day even if the fish can swim, and photograph the skin daily for the following week. Treat red swelling, white peeling, and changes in mucus as criteria for a vet visit. Review lid gap sealing and water level so jumping itself does not recur.

Two datnoids (30 cm and 25 cm) are kept in a 120 cm tank. The smaller one has been driven into a corner, its tail fin torn almost to the base, with abrasions on the flank. The larger one shows crisp stripes and keeps chasing; the smaller one has turned jet black and is not eating. The only hide is a single piece of driftwood, and water quality was good.

Which is the most appropriate first action?

1. Hit the stronger one to discipline it
2. Watch for a few days and wait for the pecking order to settle
3. Feed both more to reduce fighting
4. Move the smaller one to a quarantine tank, keep the water clean, photograph the wounds, and see a vet the same day

AnswerD. Move the smaller one to a quarantine tank, keep the water clean, photograph the wounds, and see a vet the same day

ExplanationStrongly territorial datnoids relentlessly attack the weaker fish when there is a size difference. A tail fin torn nearly to the base and abrasions are entry points for infection, and the jet-black color and food refusal show severe stress. Move the smaller fish to a quarantine tank, let it recover in clean water, photograph the wounds, and see a vet the same day. While waiting for the order to settle, the weaker fish can waste away and die. Hitting a fish is abuse and does nothing. More food does not reduce territorial fighting and fouls the water.

IssuesDatnoids of different sizes were housed together in a tank with few hides and the fighting was left unchecked. The owner read the color signs of crisp stripes and darkening but was slow to decide on isolation. No quarantine tank was ready.

ImprovementHouse datnoids only with same-sized fish, provide multiple hides, and lay out the tank to break lines of sight. Record color changes daily and set a rule to isolate after 2 days of darkening and food refusal. Keep a quarantine tank and heater on hand.

While cleaning the tank, the owner tried to move a Polypterus delhezi (30 cm) to another container with a net. The dorsal fin spines caught deep in the mesh, the fish thrashed violently, and one spine bent at the base. Several scales are stuck in the mesh. The fish is thrashing in the air. The tank is 90 cm with no other fish.

Which is the most appropriate first action?

1. Shake the net hard to drop it since it is thrashing
2. Submerge the whole net to calm the fish, then cut the mesh threads to free it
3. Pull the spines out of the net
4. Straighten the bent spine on the spot

AnswerB. Submerge the whole net to calm the fish, then cut the mesh threads to free it

ExplanationPolypterus dorsal spines tangle easily in nets, and thrashing in the air worsens spine and fin damage. First submerge the whole net to restore breathing and calm, then cut the mesh threads with scissors to free it. Pulling, shaking, or straightening the spine causes spine loss, fractures, and skin damage. Once freed, check for torn scales or bleeding, keep the water clean, and see a vet if the wounds turn cloudy white within a few days. From then on, scoop with a container instead of a net.

IssuesThe owner chose to net a spiny Polypterus, a method prone to tangling. No container or plastic bag was prepared for moving it, and the owner did not know what to do when it thrashed.

ImprovementMove Polypterus by scooping them with water in a plastic container or bag rather than a fine net. If a net must be used, choose a soft, fine-mesh material, and if it tangles, submerge the net and cut the threads. Keep scissors beside the tank at all times.

A heavy book placed on the lid as a jump deterrent fell into the tank, lid and all, during an earthquake. It struck the lungfish (80 cm) on the back, and the fish is bent in a V shape on the bottom, barely moving. The gills are moving, but it cannot rise to breathe air and is gaping.

Which is the most appropriate first action?

1. Take the fish out of the water to check its spine
2. Tempt it with food until it perks up
3. Quietly remove the fallen objects, lower the water level so it can breathe air more easily, set aeration to maximum, and contact an emergency (after-hours) animal hospital
4. Leave it as is until the shaking stops

AnswerC. Quietly remove the fallen objects, lower the water level so it can breathe air more easily, set aeration to maximum, and contact an emergency (after-hours) animal hospital

ExplanationA heavy object striking the back, leaving the fish bent in a V, unable to move or rise to breathe, is a critical state suggesting spinal or internal injury. First quietly remove the fallen objects to stop further pressure, lower the water level so the air-breathing lungfish's mouth can reach the surface, set aeration to maximum, and contact an emergency (after-hours) animal hospital. Taking it out of the water to feel the spine worsens the injury. Tempting with food is pointless, and left alone it will die unable to breathe.

IssuesAn object that is dangerous if it falls was used as a lid weight, with no thought to it falling in an earthquake. The jump deterrent caused a different accident. The owner needed to understand how serious it is when an air-breathing fish cannot surface.

ImprovementUse a heavy glass lid that locks to the tank or one with stoppers, and put nothing on top. Anchor the stand to the wall and lay anti-tip mats. Set a post-earthquake procedure: first check fallen objects, the fish's posture, and whether it can breathe air, and post the emergency (after-hours) animal hospital's contact.

One leg of the stand under a 180 cm tank has sunk slightly, the tank is tilted, water is seeping from a seam, and the floor is wet. The water level is dropping visibly and the Polypterus and lungfish are huddled on the bottom. The stand is creaking and the load appears to be on one side of the tank only.

Which is the most appropriate first action?

1. Add water to restore the level
2. Cut the power, move the fish with their tank water into a large aerated container, then inspect the tank for damage
3. Lift the tank with the fish still in it and fix the stand
4. Wipe the floor with a cloth and watch

AnswerB. Cut the power, move the fish with their tank water into a large aerated container, then inspect the tank for damage

ExplanationA leak from a sinking, tilting stand is an emergency that can lead to the tank bursting or the stand collapsing. First cut the power to prevent electric shock, move the fish with their tank water into a large aerated container or storage bin, then inspect the tank and stand for damage. Adding water increases the load and the risk of bursting. Moving the tank with fish inside risks breakage or a fall, endangering both fish and people. Wiping the floor solves nothing. Cover the container to prevent jumping.

IssuesThe stand and floor were not strong enough for the weight of a large tank. Level and floor reinforcement were not checked at setup. An evacuation container and air pump for emergencies may not have been prepared.

ImprovementPlace large tanks on a dedicated sturdy stand, check the floor's load capacity, and reinforce if needed. After setup, check for tilt regularly with a spirit level. Keep a large evacuation container, battery-powered air pump, and spare lid on hand, and share the leak procedure with the family.

Several small fish were added to the tank of a Polypterus endlicheri (45 cm). At night, the endlicheri took a small fish in its mouth but it was too big to swallow; the tail is sticking out of its mouth, which is stuck open, and it looks distressed. It cannot breathe air properly either.

Which is the most appropriate first action?

1. Pull hard on the tail sticking out of its mouth
2. Leave it until it swallows or spits it out on its own
3. Press hard on the belly to make it spit the fish out
4. Watch for a few minutes first; if it cannot spit it out, slowly pull the tail out underwater from the head side, and see a vet the same day if it will not come out

AnswerD. Watch for a few minutes first; if it cannot spit it out, slowly pull the tail out underwater from the head side, and see a vet the same day if it will not come out

ExplanationFish that fit in the mouth get swallowed whole, and if too large they lodge in the mouth or throat and cause suffocation. Fish often spit prey out on their own, so watch for a few minutes; if it cannot and breathing looks labored, slowly pull the tail out underwater, working from the head side. Pulling hard tears the mouth or throat. Pressing the belly damages the organs. Leaving it too long leads to suffocation. If it will not come out, the mouth will not close, or there is bleeding, see a vet the same day. To prevent recurrence, never house fish that fit in its mouth.

IssuesSmall fish that fit in the mouth were housed with a predatory fish. Knowing that Polypterus hunt actively at night, the owner still chose a size indistinguishable from food. The owner also did not know the emergency procedure.

ImprovementKeep only tankmates too large for the Polypterus's mouth and house small fish in a separate tank. Observe nighttime behavior and separate immediately at any sign of predation. Look up the procedure for a lodged fish, write it down, and confirm a vet you can go to.

During a water change, the drain hose was left on the floor unattended, and a Polypterus (15 cm) was carried out with the tank water spreading across the floor. The family dog is nosing it with interest. The fish is flopping on the floor and the dog is trying to pick it up in its mouth.

Which is the most appropriate first action?

1. Grab the fish with dry hands while scolding the dog
2. Put the dog in another room, pick up the fish with wet hands, return it to the tank, check for injuries, and see a vet the same day
3. Wait until the dog loses interest and moves away
4. Wrap the fish in a dry towel to protect it

AnswerB. Put the dog in another room, pick up the fish with wet hands, return it to the tank, check for injuries, and see a vet the same day

ExplanationFirst move the dog to another room to stop contact with the fish, then pick up the fish with wet hands or a wet cloth and return it to the tank. Skin pushed by the dog's teeth or nose may be injured, and combined with drying there is a risk of infection, so see a vet the same day. Dry hands or a dry towel strip the slime coat, and scolding the dog while handling may excite it into grabbing the fish. While waiting, the fish is exposed to drying and being stepped on. Fit a net on the drain intake so fish cannot be carried out.

IssuesThe owner looked away while draining and did not anticipate a small fish being sucked into the drain hose. The movement of other pets during tank work was not managed.

ImprovementFit a net or sponge on the end of the drain hose so small fish cannot be sucked in. Put dogs and cats in another room during water changes and keep them away from water on the floor. Do not leave the tank during work; deal with phone calls beforehand.

During a rushed water change, the owner forgot the dechlorinator and added tap water for half the tank. 30 minutes later, the Polypterus senegalus (25 cm) is hovering at the surface, moving its gills rapidly and gulping air repeatedly. Its mucus looks cloudy white and its movements are unsteady.

Which is the most appropriate first action?

1. Fish adapt naturally, so wait
2. Take the fish out and rinse it under running water to wash the gills
3. Add the standard dose of dechlorinator to the tank immediately, increase aeration, and see a vet the same day if no improvement
4. Feed it to distract it

AnswerC. Add the standard dose of dechlorinator to the tank immediately, increase aeration, and see a vet the same day if no improvement

ExplanationChlorine in tap water damages the gills directly; rapid gill movement, cloudy mucus, and unsteadiness are classic chlorine poisoning. First add the standard dose of dechlorinator to neutralize the chlorine and increase aeration to secure oxygen. Severe gill damage may not recover, so see a vet the same day if there is no improvement. The gills keep being damaged while you wait. Rinsing under running water exposes it to more chlorine and is fatal. It cannot digest food, which fouls the water. To prevent recurrence, make a habit of adding dechlorinator to pre-stored water before use.

IssuesThe water change was rushed and the dechlorination step was skipped. The procedure was not written as a checklist, so haste put the fish's life directly at risk.

ImprovementDraw water for changes into a separate container beforehand, add dechlorinator, and match the temperature before use. Keep the dechlorinator bottle in a fixed spot beside the tank. Write the procedure on paper and follow it step by step, especially when in a hurry.

During a renovation, the walls of the room with the tank were painted with oil-based paint. The room was ventilated, but by night the lungfish (70 cm) shakes its head each time it breathes air and is opening and closing its mouth violently at the surface. The surface has an oily sheen and the room is full of paint fumes.

Which is the most appropriate first action?

1. Move the fish to a room free of fumes, do a large water change with temperature-matched water plus activated carbon filtration and aeration, and consult an emergency (after-hours) animal hospital if neurological signs persist
2. It will be fine once the paint dries, so wait
3. Seal the lid to keep the fumes out
4. Just remove the oily film from the surface with paper

AnswerA. Move the fish to a room free of fumes, do a large water change with temperature-matched water plus activated carbon filtration and aeration, and consult an emergency (after-hours) animal hospital if neurological signs persist

ExplanationVolatile components of oil-based paint dissolve into the water from the surface, and air-breathing lungfish are hit hard because they inhale the air at the surface directly. Head shaking and violent mouth movements indicate neurological effects. First move the fish to a room free of fumes, do a large change with temperature-matched water, adsorb with activated carbon, and secure oxygen with aeration. If symptoms persist, consult an emergency (after-hours) animal hospital. The chemicals keep dissolving while the paint dries. Sealing the lid traps the contaminated surface air. Removing the film alone leaves the dissolved chemicals.

IssuesVolatile paint was used in the room with the tank with no thought to its effect on an air-breathing fish. Ventilation alone was judged safe and the fish was not moved out beforehand. No emergency adsorbent such as activated carbon was prepared.

ImprovementFor painting, fogging, insecticides, or other volatile work, move the fish to a container in another room beforehand. Do not seal the tank, and ventilate for several days after the work before bringing the fish back. Keep activated carbon and pre-conditioned water on hand and set a procedure for chemical contamination.

A strong earthquake spilled half the water from a 120 cm tank, exposing the heater so it is running dry, and the filter has stopped. The lungfish (60 cm) is unharmed but moving restlessly in the lowered water, knocking its body against the tank walls. There is no power outage.

Which is the most appropriate first action?

1. Take the fish out and put it in a container on the floor in case of aftershocks
2. First switch off the heater and filter, add temperature-matched dechlorinated water little by little to restore the level, and close the lid securely
3. Pour tap water in all at once to fill the tank
4. Feed the fish to calm it down

AnswerB. First switch off the heater and filter, add temperature-matched dechlorinated water little by little to restore the level, and close the lid securely

ExplanationAn exposed heater running dry risks damage and fire, so switch it off first. Then add temperature-matched dechlorinated water little by little to restore the level and avoid sudden water-quality changes. A restless lungfish is prone to jumping, so close the lid securely and fix the weight. Pouring tap water in at once causes poisoning from chlorine and temperature difference. A container on the floor risks tipping in an aftershock and jumping by an air-breathing fish. Feeding during the upheaval causes indigestion and fouls the water.

IssuesEarthquake measures such as anchoring the stand, preventing the tank from tipping, and securing the lid were inadequate. The owner did not know the danger of an exposed heater running dry and had no procedure for a dropped water level.

ImprovementAnchor the stand to the wall and secure the lid with stoppers. Use a heater with dry-run protection and a filter that shuts off when the water level drops. Keep pre-stored dechlorinated water on hand and post a post-earthquake checklist.

A typhoon threatens to flood the house and an evacuation order has been issued. The lungfish and Polypterus in the 180 cm tank cannot be taken along. A power outage is likely, and the evacuation is expected to last from half a day to several days. Power is on for now, the water is 26°C, and the fish are healthy. There is 1 hour before departure.

Which is the most appropriate preparation before leaving?

1. Feed generously and leave
2. Move all the fish to the bathtub and leave
3. Expecting the filter to stop in an outage, install a battery-powered air pump, secure the lid, stop feeding, cover the tank with insulation, and then evacuate
4. Replace all the tank water before leaving

AnswerC. Expecting the filter to stop in an outage, install a battery-powered air pump, secure the lid, stop feeding, cover the tank with insulation, and then evacuate

ExplanationSince a large tank cannot be taken, prepare to raise the odds of survival while you are away before evacuating. Assuming the filter and heater will stop in an outage, install a battery-powered air pump, secure the lid against jumping, stop feeding to prevent water deterioration, and cover with insulation. Ancient fish can go without food for several days. Generous feeding rapidly fouls the water with leftovers and waste. The bathtub carries risks of chlorine, detergent residue, and jumping. A full water change loses the filter bacteria and the water collapses while you are away.

IssuesThere was no preparation for a disaster in which large fish cannot be taken along. Stocks of battery-powered air pumps, insulation, and lid fasteners were lacking. The owner needs to know roughly how long the fish can go unfed and how to think about water quality during evacuation.

ImprovementKeep a battery-powered air pump with spare batteries, foam, and blankets near the tank. Make the lid lockable with stoppers. Post a written procedure for disasters (stop feeding, prioritize oxygen and insulation) and designate someone who can check on the fish after evacuation.

Late on a July night, the tank chiller failed and the water rose to 31°C. The Polypterus endlicheri (55 cm) is breathing air frequently, and the datnoid (30 cm) is gaping near the surface with faded color. Room temperature is 30°C, the air conditioner is usable, and a cooling fan is at hand.

Which is the most appropriate first action?

1. Put frozen plastic bottles directly in the tank to cool it fast
2. Lower the room temperature with the air conditioner, set the cooling fan and aeration to maximum, and do small changes with slightly cooler water to lower the temperature in stages
3. Move the fish to a bucket chilled in the refrigerator
4. Do nothing and let them endure until morning

AnswerB. Lower the room temperature with the air conditioner, set the cooling fan and aeration to maximum, and do small changes with slightly cooler water to lower the temperature in stages

Explanation31°C is a dangerous temperature due to oxygen shortage and metabolic strain; increased air breathing and gaping at the surface are signs of oxygen deprivation. First lower the room temperature with the air conditioner, use the cooling fan for evaporative cooling, and set aeration to maximum to add oxygen. Do small water changes with slightly cooler water, dropping 1–2°C at a time. Frozen bottles placed directly cause local rapid cooling and ill health. A refrigerator-chilled bucket is fatal from the large temperature difference. Left until morning, the fish risk dying of exhaustion.

IssuesNo backup was prepared for a chiller failure. With no habit of checking the water temperature on summer nights and no alarm, the problem may have been noticed late. Understanding the importance of oxygen supply is key to the response.

ImprovementInstall a thermometer with a high-temperature alarm and keep a cooling fan as a backup in summer. Run the air conditioner at night too, and set procedures for outages and chiller failure. Run aeration stronger throughout summer to increase dissolved oxygen.

A net used in the tank of a datnoid quarantined with columnaris was used, unwashed, in the Polypterus tank as well. 2 days later, the edge of the Polypterus's tail fin is starting to turn cloudy white and the area around its mouth is whitish. Water temperature is a stable 26°C.

Which is the most appropriate first action?

1. Disinfect the net with boiling water, stop sharing it, isolate the Polypterus and see a vet the same day, and dedicate equipment to each tank
2. Polypterus are hardy, so watch and wait
3. Replace all the water in both tanks to wash the disease away
4. Put the datnoid's medication straight into the Polypterus tank

AnswerA. Disinfect the net with boiling water, stop sharing it, isolate the Polypterus and see a vet the same day, and dedicate equipment to each tank

ExplanationColumnaris bacteria spread between tanks via equipment. Once the Polypterus shows cloudy white fins or mouth, infection is strongly suspected, and since it progresses fast, isolate it and see a vet the same day. Disinfect the net with boiling water or similar and dedicate equipment to each tank from now on. Leaving it because Polypterus are hardy can cost its life within days. A full water change causes water-quality collapse and sudden change, and the bacteria remain on the fish. Reusing the datnoid's medication on your own judgment is dangerous as species and symptoms differ; always follow the vet's instructions.

IssuesEquipment used in a sick fish's tank was used in another tank without disinfection, spreading the infection. The fish was isolated, but the infection route via shared equipment was overlooked. No disinfection procedure had been set.

ImprovementColor-code nets, buckets, hoses, and tongs and dedicate them to each tank. Treat equipment used in a sick fish's tank with boiling water or disinfectant immediately after use and dry completely before reuse. Always tend sick fish after the healthy tanks.

At every water change, tank water was poured down the kitchen sink and tank equipment was washed there too. Recently a family member developed diarrhea and fever, and the doctor raised the possibility of Salmonella. The home has lungfish and Polypterus tanks, and equipment and dishes were washed with the same sponge.

Which is the most appropriate course of action going forward?

1. Give up all the fish since they are the source of infection
2. Pour tank water down the toilet or an outdoor drain, wash equipment outside the kitchen with a dedicated sponge, wash hands with soap after work, and tell the doctor you keep fish
3. Disinfecting the dishes is enough
4. Boil the tank water before pouring it out

AnswerB. Pour tank water down the toilet or an outdoor drain, wash equipment outside the kitchen with a dedicated sponge, wash hands with soap after work, and tell the doctor you keep fish

ExplanationTank water, substrate, and equipment can contain bacteria such as Salmonella, so pouring it out in the kitchen or washing with the same sponge as the dishes contaminates food. Pour tank water down the toilet or an outdoor drain, wash equipment in the bathroom or outdoors with a dedicated sponge and container, and wash hands with soap after work. Tell the doctor you keep fish. There is no need to give up the fish; better hygiene prevents it. Disinfecting dishes alone leaves the root route in place. Boiling is impractical, and the habit of pouring into the sink itself must change.

IssuesTank water and fish equipment were handled in the kitchen without separation from food hygiene. Low awareness of zoonoses from fish put the family's health at risk.

ImprovementPour tank water down the toilet or outdoors, and wash equipment with a dedicated sponge and bucket in the bathroom or outdoors. Make hand washing after tank work a family rule. Households with small children or elderly members should be especially strict about hand washing and separating equipment.

At 11 p.m., a Polypterus endlicheri (50 cm) was found on the floor 2 hours after jumping. The skin is dry and the gill covers are barely moving, but when held with wet hands the mouth opens and closes slightly and the tail twitches faintly. The tank water is 26°C, and an air pump and the emergency (after-hours) animal hospital's contact are at hand.

Which is the most appropriate first action?

1. Press on the chest to perform cardiac massage
2. Blow air into its mouth like rescue breathing
3. It is dry, so conclude it is dead
4. Return it to the tank, set aeration to maximum, support it and move it slowly back and forth so water flows from the mouth over the gills, and contact an emergency (after-hours) animal hospital

AnswerD. Return it to the tank, set aeration to maximum, support it and move it slowly back and forth so water flows from the mouth over the gills, and contact an emergency (after-hours) animal hospital

ExplanationHuman-style cardiac massage and rescue breathing do not apply to fish; resuscitation is fundamentally about oxygen supply in the water. If the mouth or tail moves even slightly, return it to the tank, set aeration to maximum, and move it slowly back and forth so water flows from the mouth over the gills to take in oxygen, keeping the lights off and the fish quiet while contacting an emergency (after-hours) animal hospital. Pressing the chest damages the organs, and blowing into the mouth is pointless and carries an infection risk for you. Never declare a responsive fish dead.

IssuesIt took 2 hours from the jump to discovery, with no way to notice a nighttime jump. Lid and gap measures were inadequate. Knowing that fish resuscitation differs from human first aid is what separates life from death.

ImprovementSeal the lid gaps completely and keep the water level at least 5 cm below the lid. Make checking the lid and gaps a habit before bed. Write the fish resuscitation steps (support underwater and supply oxygen, keep quiet, see a vet) on paper and keep the air pump and contact beside the tank.

A lungfish (80 cm) slammed itself hard against the edge of a rock in the tank; scales over a wide area of the flank are torn off and bleeding. The water is faintly red and the fish is starting to tilt onto its side on the bottom. When the owner reaches in to press on the bleeding, the lungfish opens its mouth in threat. It is 8 p.m.

Which is the most appropriate first action?

1. Take the fish out and press gauze on the wound
2. Add human medication to the tank as a hemostatic
3. Without putting your hands in, quietly remove the rock, increase aeration, do a water change with temperature-matched water, take photos, and contact an emergency (after-hours) animal hospital
4. Do nothing until the bleeding stops

AnswerC. Without putting your hands in, quietly remove the rock, increase aeration, do a water change with temperature-matched water, take photos, and contact an emergency (after-hours) animal hospital

ExplanationBleeding in fish cannot be stopped with pressure as in humans; taking it out of the water worsens it through drying and thrashing, and a lungfish may bite. First, without putting your hands in, quietly remove the rock to prevent recurrence, increase aeration, and do a change with temperature-matched water to keep the water clean. A fish tilting over with continued bleeding needs a vet right now, so take photos and contact an emergency (after-hours) animal hospital. Human hemostatics cannot be used on fish and foul the water. Left alone it dies from blood loss and infection.

IssuesA rock with sharp edges was kept in a lungfish tank. The lungfish's habit of thrashing and striking its body was not considered, and layout safety was neglected. Trying to reach in and treat a biting fish was also a dangerous decision.

ImprovementFurnish a lungfish tank only with items it cannot be hurt on, such as smooth driftwood or PVC pipe, or keep it bare-bottom. Write down the bleeding procedure (hands out, oxygen and water quality, see a vet). Check in advance whether an emergency (after-hours) animal hospital that sees fish is available.

After calling an emergency (after-hours) animal hospital, the owner was told to bring in the lungfish (70 cm), which has a swollen abdomen and has rolled onto its side. The hospital is 40 minutes away by car. It is January and the outside temperature is 3°C. At hand are a large plastic bag, a styrofoam box, an air pump, and rubber gloves. The lungfish occasionally opens its mouth and tries to bite.

Which is the most appropriate transport method?

1. Take the fish out, wrap it in a wet towel, and carry it on your lap
2. Put a small amount of tank water in a double bag with plenty of air, insulate in the styrofoam box, keep it dark, and transport
3. Carry it in a bucket full of tank water with no lid
4. Put tap water in the bag and transport

AnswerB. Put a small amount of tank water in a double bag with plenty of air, insulate in the styrofoam box, keep it dark, and transport

ExplanationTo transport a lungfish, double-bag it in case of bite-through, use only enough tank water to cover the body with plenty of air, insulate in a styrofoam box, and keep it dark. Less water means less thrashing and it can still breathe air. Insulation matters so the water does not cool in the winter air. A wet towel on your lap risks drying, dropping, and bites. A full bucket spills with motion, and no lid means it can jump out. Tap water damages the gills with chlorine. On arrival, report water temperature and quality data and the course of symptoms.

IssuesThe bag and box were prepared, but the owner needed to know in advance about lungfish-specific bite-through and transport in shallow water. Winter insulation and darkness are also important points.

ImprovementKeep a transport kit (double bags, styrofoam box, air pump, rubber gloves, disposable heat packs) near the tank. Confirm the location of and travel time to the emergency (after-hours) animal hospital and write down transport precautions. Save water-quality data and symptom records on your smartphone.

A Polypterus senegalus (25 cm) is motionless on the bottom. Counting the gill cover movements gives about 20 per minute, clearly fewer than usual. It responds weakly to touch. No air breath has been seen for over an hour. Water temperature 25°C, ammonia and nitrite zero; in yesterday's water change the new water went in 5°C too cold.

Which is the most appropriate assessment and action for this state?

1. Slow gills mean it is resting, so do not touch it
2. Treat the reduced breathing rate and weak response as signs of serious weakening, stabilize the temperature, increase aeration, and see a vet the same day
3. Raise the water temperature to 30°C at once to make it breathe faster
4. Put food in front of it and watch its reaction

AnswerB. Treat the reduced breathing rate and weak response as signs of serious weakening, stabilize the temperature, increase aeration, and see a vet the same day

ExplanationGill cover movement clearly below normal, no air breath for over an hour, and a weak response are serious signs of slowed metabolism and weakening in a Polypterus. Yesterday's sudden 5°C drop is the likely trigger. First stabilize the temperature, increase aeration to secure oxygen, turn off the lights to keep it quiet, and see a vet the same day. Mistaking it for rest and leaving it means it will be too late. A sudden rise to 30°C piles one shock on another and worsens it. Testing with food is pointless; it cannot digest even if it eats.

IssuesThe new water was added 5°C too cold, causing a sudden change. Knowing the normal gill rate and air-breathing interval was good, but there was a risk of misreading the abnormality as 'calm.' No criteria for seeing a vet had been set.

ImprovementMatch new water to within 1°C of the main tank before adding it. Record the normal gill cover rate and air-breathing interval, and set a rule that half or less, or double or more, is abnormal. Write down the procedure for a weakened fish (stabilize temperature, oxygen, quiet, see a vet the same day).

At 1 a.m., a datnoid (30 cm) has rolled onto its side on the bottom; the gill covers move slowly but it cannot right itself. Its color is jet black, and it is a species that does not breathe air. The emergency (after-hours) animal hospital cannot see it until 6 a.m., but it will be seen first thing in the morning. Water temperature 26°C; a trace of ammonia was detected.

Which is the most appropriate care during the 5 hours before the visit?

1. Lay the fish in a container with a little water to float it near the surface
2. Do nothing; darken the room and leave it
3. Feed it to build strength
4. Set aeration to maximum, do a 1/3 water change with temperature-matched water to lower ammonia, turn off the lights to keep it quiet, and record the gill movements every 30 minutes

AnswerD. Set aeration to maximum, do a 1/3 water change with temperature-matched water to lower ammonia, turn off the lights to keep it quiet, and record the gill movements every 30 minutes

ExplanationA datnoid, which can only breathe through its gills, rolled over and sunk is critical, and the most important things before the visit are oxygen supply and water-quality improvement. Set aeration to maximum, do a 1/3 change with temperature-matched water to lower ammonia, and turn off the lights to keep it quiet. Recording gill movements every 30 minutes provides information for the vet. Laying it in a container with a little water leaves the gills out of the water and it suffocates. Doing nothing lets ammonia make it worse. It cannot digest food, which fouls the water further. Bring the water-quality data and records first thing in the morning.

IssuesA trace of ammonia was detected, possibly reflecting reduced filter capacity or overfeeding. The warning sign of darkening color was missed. In an area with limited after-hours options, advance preparation was important.

ImprovementReview water changes and feeding amounts so ammonia stays at zero at all times. Record the datnoid's color daily and make it a habit to test the water when darkening persists. Find out in advance whether a hospital that sees fish at night exists, and post a written procedure for care before the visit (oxygen, water quality, quiet, records).