Catfish & plecos case method: 50 questions

You have kept 6 cory catfish in a 60 cm tank for 3 months. The bottom is covered with large, sharp-edged gravel chosen for its looks. Observing at night after lights-out, two fish have barbels that are clearly shorter than before, and their snouts are red and raw. When you drop in food tablets they cannot find them, and the other fish eat them. You change water about once every 2 weeks.

Which is the most appropriate first action?

1. Barbels grow back on their own, so increase the food and wait
2. Replace the gravel with fine, smooth sand, siphon the dirt off the bottom, and change water
3. Add double the labeled dose of fish medication for the red snouts to cure it quickly
4. Switch to floating food so they do not need to use their barbels

AnswerB. Replace the gravel with fine, smooth sand, siphon the dirt off the bottom, and change water

ExplanationCory catfish use the barbels around their mouth to probe the bottom for food. Sharp gravel and dirt accumulated on the bottom injure the barbels and snout, and bacterial infection erodes the barbels. It will not heal unless the cause is removed, so the first response is to switch to fine sand, clean the bottom, and change water. More food means more waste and makes it worse. Catfish are sensitive to medication; a double dose causes poisoning. Floating food never reaches bottom-dwelling fish and leads to starvation. In a clean environment the barbels gradually regrow, but if the snout turns white and crumbles and the fish cannot eat, consult a fish-knowledgeable shop or vet within a few days.

IssuesThe owner chose gravel for looks without knowing bottom-dweller biology, and settled for water changes every 2 weeks, which let dirt build up on the bottom. They did not notice the fish could not find food, so chronic malnutrition was also present.

ImprovementGive cory catfish a thin layer of smooth field sand or river sand, and siphon the bottom during a weekly 1/3 water change. Feed sinking tablets before lights-out and check daily that everyone is eating by looking at barbels and belly fullness.

You have kept one sailfin pleco with angelfish in a 90 cm tank for six months. You were told the pleco eats algae off the glass and does not need food, so you have never given it a dedicated diet. Lately the glass is always spotless and the pleco comes out and roams during the day. On close inspection, its belly is caved inward and its eyes are sunken.

Which is the most appropriate assessment of this situation?

1. Getting slim on algae is a sign of health, so continue as is
2. Dump in a large amount of food at once and let it eat until its belly swells
3. Judge it to be near starvation and feed vegetable tablets and boiled vegetables every day after lights-out
4. Being active in daytime means disease, so treat with a medicated bath

AnswerC. Judge it to be near starvation and feed vegetable tablets and boiled vegetables every day after lights-out

ExplanationAlgae alone does not provide enough nutrition for a pleco, and once the tank's algae is gone it starves. A sunken belly and hollow eyes are signs of imminent starvation, and roaming during the day is desperate food-seeking behavior. The only remedy is to feed vegetable tablets, boiled vegetables, and driftwood to rasp on every day after lights-out. Dumping in a large amount at once leaves uneaten food that fouls the water and further burdens a weakened body. Calling it a sign of health is wrong, and a medicated bath is unnecessary and highly toxic to a weakened fish. If it does not eat after several days of feeding, consult a fish-knowledgeable shop or vet the same day.

IssuesThe owner believed the myth that plecos are algae cleaners, gave no dedicated food, and missed the progressive weight loss. They had no habit of watching a nocturnal fish eat and did not know to judge nutritional status by belly fullness.

ImprovementFeed plecos vegetable tablets every day before lights-out and keep cured driftwood in the tank at all times. Once a week view the belly and eyes from the side; if you see weight loss, reconsider feeding amount and frequency. Treat algae as a snack, not a diet.

At 5 a.m. on a summer morning, the redtail catfish (40 cm) and two plecos in a 120 cm tank are near the surface, moving their gills violently and listing sideways. Last night you fed a large amount of frozen fish and leftovers remain on the bottom. The water is slightly cloudy and smells fishy. A nitrite test strip shows the darkest color.

Which is the most appropriate first action?

1. Replace all the water with fresh tap water to remove the dirt completely
2. Do a 1/3 water change with dechlorinated water at the same temperature, turn aeration to maximum, and siphon out the leftovers
3. Add several times the labeled dose of bacteria supplement to break down the nitrite
4. Take the fish out into a bucket of fresh water and scrub the whole tank

AnswerB. Do a 1/3 water change with dechlorinated water at the same temperature, turn aeration to maximum, and siphon out the leftovers

ExplanationLarge catfish produce a lot of waste and leftovers, so they easily suffer nitrite and ammonia poisoning. Violent breathing at the surface and rolling over are that sudden crisis; the correct response is a 1/3 water change with same-temperature dechlorinated water, maximum aeration, and siphoning out the leftovers. Stop feeding and do another 1/3 change the next day. A full water change or scrubbing the tank loses the filter bacteria, and the sudden change in water quality and pH finishes off weakened fish. Overdosing bacteria supplement has no immediate effect and increases oxygen consumption. Tap water in a bucket is dangerous because of chlorine and the temperature difference. If any fish is still rolling after the water change, phone a fish-knowledgeable vet right now.

IssuesFiltration capacity and water-change frequency were inadequate for the waste output of large fish. The owner left the leftover frozen fish from a heavy night feeding and missed the warning signs of cloudy, smelly water. Nitrite was never measured regularly.

ImprovementFor large catfish, do a 1/3 water change twice a week and always siphon leftovers the next morning. Test nitrite weekly with strips and record it. Upgrade the canister filter and run aeration at all times. Feed only as much frozen fish as will be finished.

In November you put a bristlenose pleco that arrived by mail order straight into a 60 cm tank without quarantine. Four days later, white spots are scattered over the pleco and the cory catfish, and they are rubbing against the driftwood. Water temperature is 23°C. You read online that white spot disease is treated with fish medication, and you have goldfish medicine on hand.

Which is the most appropriate response?

1. Add the goldfish dose to the tank and wait until tomorrow
2. Raise the temperature 1–2°C per day to 27–28°C, do a 1/3 water change, and start medication at half the labeled dose while watching
3. Remove the white spots with tweezers
4. Raise the temperature to 30°C at once to kill the parasites the same day

AnswerB. Raise the temperature 1–2°C per day to 27–28°C, do a 1/3 water change, and start medication at half the labeled dose while watching

ExplanationWhite spot disease (ich) breaks out with falling temperatures and new arrivals. The basics are raising the temperature 1–2°C per day to 27–28°C and doing a 1/3 water change to reduce free-swimming parasites. Catfish and plecos have few scales and are sensitive to medication, so if you use fish medicine start at half the labeled dose, and dilute with a water change if breathing becomes labored. Adding the full goldfish dose risks fatal poisoning. The spots are embedded in the skin and cannot be removed with tweezers; you will only cause wounds. Jumping to 30°C causes temperature shock. If there is no improvement or it spreads over the whole body, consult a fish-knowledgeable shop or vet the same day.

IssuesThe owner added the newcomer to the main tank without quarantine and spread the infection to the existing fish. Temperature management for the November cooldown was lax, and they did not know catfish are sensitive to medication.

ImprovementObserve new arrivals in a separate container for 1–2 weeks before adding them. In autumn keep 25–27°C stable with a heater. Confirm with the shop in advance how to medicate catfish and plecos, and keep a quarantine container ready.

The redtail catfish (3 years old, 60 cm) in a 150 cm tank has not eaten for 2 days and sits motionless on the bottom. This morning its belly is bulging on both sides, there are red hemorrhagic spots on the body, and the fin bases are congested. You skipped a water change last week and dirt has built up on the bottom.

Which is the most appropriate first action?

1. Stop feeding, change water, take photos and video, and phone a vet who sees fish the same day
2. Press on the belly with your hands to expel the contents and relieve the swelling
3. Mix human antibiotics into the food and feed it
4. Put in its favorite frozen fish every day until its appetite returns

AnswerA. Stop feeding, change water, take photos and video, and phone a vet who sees fish the same day

ExplanationAbdominal swelling, hemorrhagic spots, and raised scales indicate a serious bacterial infection such as Aeromonas, triggered by poor water quality. Large fish are hard to isolate, so first stop feeding, change water with same-temperature dechlorinated water to clean the environment, take photos and video, and consult a vet who can see fish the same day. Pressing the belly damages the organs, and the spines and bite can injure the owner. Human medicine is dangerous because the dose for fish is unknown. Continuing to put frozen fish in with a weakened fish leaves leftovers that further foul the water. Treating a large fish requires calculating bath volumes, so leave it to a professional rather than guessing.

IssuesThe owner neglected water changes matching the waste output of a large fish and left dirt on the bottom. They did not act at the early sign of 2 days without eating and noticed only after it became severe. They had not looked up a vet who could see large fish.

ImprovementFor large catfish, strictly keep a 1/3 water change and bottom cleaning twice a week. If it skips a day of eating, test the water; if it continues 2 days, seek advice. Find a vet who sees large fish at the time of purchase and post the phone number near the tank.

A midsummer evening, a 45 cm tank in a room without air conditioning. Eight cory catfish dash to the surface several times a minute to gulp air, and move their gills rapidly once back on the bottom. The thermometer reads 31°C. There is no aeration, only the flow from a hang-on filter. The water is clear and test strips detect no nitrite.

Which is the most appropriate first action?

1. Cory catfish breathe air, so this is normal behavior; nothing needs to be done
2. Put ice directly in the tank to drop the temperature quickly
3. Add aeration, lower the temperature gradually with a cooling fan, and turn off the lights
4. Add fish medication to treat a respiratory disease

AnswerC. Add aeration, lower the temperature gradually with a cooling fan, and turn off the lights

ExplanationCory catfish can breathe air through the gut, but surfacing several times a minute is a sign of low oxygen in the water. A high temperature of 31°C reduces dissolved oxygen and raises the fish's oxygen demand. Add aeration, lower the temperature gradually with a cooling fan or room air conditioning, and turn off the lights to limit heating and stimulation. Putting ice straight in causes localized rapid cooling and temperature shock. If you mistake this for normal behavior and leave it, oxygen drops further overnight and the fish die by morning. With no nitrite and clear water this is not an infection; medication is unnecessary and only adds stress. If there is no improvement the same day, consult a fish-knowledgeable shop.

IssuesThere was no cooling equipment or aeration against midsummer heat, and the owner lacked the knowledge to tell air-breathing from distress. Checking the temperature daily was not a habit.

ImprovementInstall a cooling fan or chiller in summer and act immediately if the water exceeds 30°C. Run aeration year-round. Watch daily how often the corys surface, and suspect low oxygen if it increases.

Winter, an unheated 90 cm tank with a Japanese catfish (Amur catfish, 35 cm). Last week while netting it, the pectoral spine got tangled and the base was scraped. Today there is cotton-like white fluff around that wound, and it is spreading a little. Water temperature has dropped to 12°C and water has not been changed for a month.

Which is the most appropriate response?

1. Scrub off the cotton-like growth with a brush and apply antiseptic to the wound
2. Change water to clean it, raise the temperature 1–2°C per day with a heater to 18–20°C, and let the wound heal
3. Japanese catfish are native and cold-hardy, so leave it until spring
4. Raise the temperature to 28°C at once to kill the fungus

AnswerB. Change water to clean it, raise the temperature 1–2°C per day with a heater to 18–20°C, and let the wound heal

ExplanationCotton-like white growth on a wound is water mold (fungus), which spreads in cold, dirty water. First change water to reduce organic matter, then raise the temperature 1–2°C per day with a heater to 18–20°C to boost the fish's healing, and let the wound recover. Japanese catfish tolerate cold, but with the combination of a wound and dirty water the fungus advances and the fish dies. Scrubbing with a brush strips the protective slime coat and spreads infection, and human antiseptics are toxic to fish. Jumping from 12°C to 28°C causes temperature shock. If the growth spreads to the mouth or gills, consult a fish-knowledgeable shop or vet the same day.

IssuesThe owner tangled the spine in a net and caused a wound, and the winter cold plus a month without water changes invited fungus. They over-trusted the Japanese catfish as a tough fish and neglected to watch the wound.

ImprovementMove catfish without a net, scooping them with water in a container. Install a heater to keep at least 15°C even in winter, and keep weekly water changes. If a fish is wounded, isolate it, check the wound daily, and act immediately if cotton-like growth appears.

The royal pleco (20 cm) in a 90 cm tank has come out from behind the driftwood and is rapidly moving only one gill. The gill cover stays slightly open and the inside looks whitish. The other fish are fine. Last week you added a cheap imported piece of driftwood; the water is a little brown and pH has fallen below 6.

Which is the most appropriate first action?

1. Open the gill cover by hand and clean inside with a cotton swab
2. Add pH adjuster all at once to bring it back to 7.0
3. Remove the new driftwood, do a 1/3 water change at the same temperature, increase aeration, take photos, and seek advice
4. The other fish are fine, so treat it as the pleco's quirk and keep watching

AnswerC. Remove the new driftwood, do a 1/3 water change at the same temperature, increase aeration, take photos, and seek advice

ExplanationMoving only one gill with a whitish interior indicates gill damage from parasites, bacteria, or water quality, and left alone it kills by respiratory failure. The likely cause is uncured driftwood that dropped the pH sharply and hurt the gills. Remove the driftwood, do a 1/3 water change at the same temperature, increase aeration, take photos or video of the gills, and consult a fish-knowledgeable shop or vet the same day. Prying the gill cover open destroys the delicate gills. Dumping in pH adjuster causes pH shock. Even if the other fish are fine, gill symptoms are urgent and waiting is dangerous.

IssuesThe owner added cheap, uncured driftwood and caused a sudden pH drop. Despite the warnings of discolored water and falling pH, they did not act and noticed only when the gill abnormality appeared.

ImprovementCure driftwood by boiling and soaking for several days, and test pH before adding it. For a week after adding any new item, check pH and the fish's breathing daily. Make a habit of watching gill movement and color, and remember that one-sided movement is an emergency.

While netting a cory catfish for cleaning, its hard pectoral spine pierced the mesh and got tangled. The fish is thrashing in the net and the spine is deeply caught. Pulling the net looks like it would bend the spine. The fish has already been out of the water for about 20 seconds.

Which is the most appropriate first action?

1. Return the fish to the water still in the net, then cut the mesh with scissors to free the spine
2. Pinch the spine with your fingers and twist it the opposite way to free it
3. Shake the net hard to drop the fish out
4. Let it dry while tangled and free it once it stops moving

AnswerA. Return the fish to the water still in the net, then cut the mesh with scissors to free the spine

ExplanationThe pectoral and dorsal spines of corys and plecos easily tangle in nets, and forcing them breaks the spine or tears its base, opening the door to fungus and bacterial infection. First return the fish to the water net and all to calm its breathing and thrashing, then cut the mesh with scissors to release the spine. Twisting with fingers breaks the spine and can pierce your own finger, causing secondary infection. Shaking tears the spine or drops the fish on the floor. Letting it dry to weaken it damages the slime coat and gills and risks death. After freeing it, isolate and watch the wound, and treat for fungus if cotton-like growth appears.

IssuesThe owner used an ordinary net without knowing the structure of catfish spines. They did not know how to handle a tangled fish and had no tools such as scissors at hand, so the time out of water dragged on.

ImprovementMove catfish and plecos without a net, scooping them with water in a plastic cup or container. If a net is unavoidable, use a fine-mesh vinyl one. Keep small scissors near the tank and decide in advance to cut underwater if tangled.

At 7 a.m. you find the pleco (15 cm) lying on the floor in front of the tank. You went to bed last night with the lid shifted. Its skin is somewhat dry and the fins are curled, but the gill cover is moving slightly. There is a small puddle on the floor; the tank is at 26°C and the other fish are swimming normally.

Which is the most appropriate first action?

1. Wrap it in a dry cloth to warm it before returning it to the tank
2. Judge it dead and put it in a trash bag
3. Pick it up with wet hands, return it to the tank, hold its mouth into the current to pass water over the gills, and increase aeration
4. Rinse the dust off its body under the tap before returning it

AnswerC. Pick it up with wet hands, return it to the tank, hold its mouth into the current to pass water over the gills, and increase aeration

ExplanationPlecos and catfish are active at night and prone to jumping out, but their slime-protected skin is relatively tolerant of drying. If the gill cover is moving there is a chance of recovery: pick it up with wet hands, hold it gently in the tank with its mouth facing the current so water passes over the gills, and set aeration to maximum. Do not give up for 30 minutes. A dry cloth strips the slime coat, and declaring it dead is premature. Tap water burdens a weakened fish with chlorine and a temperature difference. Afterward turn off the lights, watch for several days for fungus or red spots, and if they appear isolate the fish and keep the water clean.

IssuesThe owner knew the fish was nocturnal and prone to jumping yet left the lid shifted. There was no weight on the lid or gap-proofing, and no one in the family knew how to revive a fish that had jumped out.

ImprovementAlways close the lid and weight it down. Plug cable holes and gaps with sponge. Make a habit of checking the lid is closed before turning off the lights at night. Share the jump-out procedure with the family.

A 90 cm tank in winter. The pleco (12 cm) had been clinging behind an unguarded heater for a long time. One morning there is a white, burned-looking band on its underside and the skin is peeling. The pleco sits motionless in the shade of the driftwood and does not respond to tablets given after lights-out. The water is 26°C and water quality is normal.

Which is the most appropriate response?

1. Apply human burn ointment to the burned skin and return it to the tank
2. Keep it in an isolation container with clean water at 25–27°C, fit a heater guard, and seek advice the same day if it worsens
3. The wound heals on its own, so do nothing and leave the heater as is
4. Lower the water temperature to 20°C to cool the burn

AnswerB. Keep it in an isolation container with clean water at 25–27°C, fit a heater guard, and seek advice the same day if it worsens

ExplanationBottom-dwelling plecos and catfish press their bodies against heaters and get burned easily. The white burned area has lost its slime coat and becomes an entry point for fungus and bacteria. Keep it in an isolation container with clean water at 25–27°C and let the wound recover. At the same time fit a heater guard to prevent a recurrence. If red spots or cotton-like growth spread or it keeps refusing food, consult a fish-knowledgeable shop or vet the same day. Human burn ointment is toxic to fish and dissolves into the water. Without a guard it will be burned again. Lowering the temperature reduces immunity, slows healing, and invites fungus.

IssuesThe owner did not know bottom dwellers cling to heaters and used one without a guard. Because the fish hides by day there were few chances to see its underside, so the burn was noticed late.

ImprovementAlways fit a guard on the heater and place it where water flows past. Once a week after lights-out, check the fish's underside and body with a flashlight. Keep an isolation container and aeration on hand so an injured fish can be isolated at once.

You keep 5 cory catfish with a 20 cm bichir in a 90 cm tank. In the morning one cory has lost half its tail fin and has tooth-mark wounds on its side. Another is missing. The remaining corys huddle motionless in a corner, and the bichir rests under the driftwood with a swollen belly.

Which is the most appropriate first action?

1. Isolate the injured cory, move the rest to a separate tank, and let them recover in clean water
2. Rub fish medication directly into the wound
3. Feed the bichir more so it stops attacking the corys
4. The wounds are small, so keep watching and continue keeping them together

AnswerA. Isolate the injured cory, move the rest to a separate tank, and let them recover in clean water

ExplanationNocturnal large fish attack small bottom dwellers at night, and the missing fish was most likely swallowed. The correct response is to isolate the injured fish to recover in clean water and move the rest to a separate tank where they cannot be attacked. A cory's spines can lodge in a large fish's throat and kill both. Rubbing medication onto a wound damages the slime coat and does nothing. More food does not stop predatory instinct and fouls the water. Continuing to keep them together loses the remaining fish too. After isolation, if cotton-like growth or red spots appear on the wounds, consult a fish-knowledgeable shop or vet the same day.

IssuesThe owner kept fish together with a size gap that fit in the predator's mouth. They did not know large nocturnal fish attack small fish at night and never observed behavior after lights-out. No emergency isolation container was prepared.

ImprovementOnly keep fish together that cannot fit in each other's mouths; keep large catfish and carnivorous fish alone as a rule. Check behavior after lights-out for a week after introducing tankmates. Keep a spare tank and aeration ready for emergency isolation.

While holding down the redtail catfish (70 cm) in a 150 cm tank bare-handed to rearrange the layout, it thrashed and its dorsal spine pierced deep into your palm. When you pull your hand the spine catches and will not come out, and the fish keeps thrashing at the surface. You have started bleeding.

Which is the most appropriate first action?

1. Bear the pain and yank your hand off
2. Stop moving, return the fish to the water to calm it, then withdraw slowly along the direction it went in
3. Lift the fish out of the water onto the floor and remove the spine with both hands
4. Go to the hospital with the fish still attached

AnswerB. Stop moving, return the fish to the water to calm it, then withdraw slowly along the direction it went in

ExplanationCatfish spines have backward-facing serrations; yanking tears the wound and can snap the spine off inside you. First stop moving, return the fish to the water to calm its thrashing, then withdraw slowly along the direction of entry. Taking the fish out onto the floor dries it, breaks the spine, and causes more thrashing and more stab wounds. Carrying it still attached is dangerous for both fish and person. Afterward rinse under running water, squeeze out a little blood, and disinfect. Spine wounds easily pick up tank bacteria, so if swelling or throbbing pain persists, see a doctor and say the injury happened during aquarium work.

IssuesThe owner underestimated the danger of a large catfish's spines and held it bare-handed. They had no tools to guide the fish, thick gloves, or a divider ready for the layout change.

ImprovementWear thick gloves for any work touching a large catfish, and use a divider to confine it to one side first. Learn the procedure for a spine injury in advance and keep a first-aid kit and antiseptic near the tank. Do not work alone; ask for a helper.

In a 60 cm tank, one cory catfish has gone headfirst into a narrow gap in the driftwood and its spines have caught so it cannot get out. It spreads its pectoral fins and struggles to back out, and part of its skin is scraped white. You found it late at night after lights-out, and the other corys are swimming anxiously around it.

Which is the most appropriate first action?

1. Grab the tail and pull it out backward hard
2. Gently lift the whole driftwood underwater and widen the gap or tilt it so the fish can get out on its own
3. It will free itself by morning, so go to sleep
4. Take the driftwood out of the tank and remove the fish outside

AnswerB. Gently lift the whole driftwood underwater and widen the gap or tilt it so the fish can get out on its own

ExplanationA cory with spines spread cannot easily back out; pulling the tail breaks the spines and tears their bases, causing serious injury. The safe method is to gently lift the whole driftwood underwater and widen the gap, or tilt it to an angle where the fish can move forward and escape by itself. Left until morning, it may die from exhaustion, oxygen shortage, or fungus and bacterial infection in the scraped skin. Taking the driftwood out of the water dries the fish and digs the spines in. After escape, keep it in an isolation container with clean water, watch the scraped area for several days for cotton-like growth or red spots, and seek advice the same day if they appear.

IssuesThe owner added driftwood with gaps narrower than the fish's body without considering the trapping risk. They had no habit of observing after lights-out, so discovery came late at night.

ImprovementChoose hides and driftwood with openings well wider than the fish, and plug narrow gaps with filter wool or silicone. Provide more pipes or shelters than there are fish. Check everyone's position with a flashlight an hour after lights-out.

Late at night in January, a local power outage unrelated to a typhoon. The heater and filter on a 90 cm tank stopped, and 2 hours later the water has dropped to 17°C. The pleco and corys sit motionless on the bottom with slow gill movement. There is no word on when power returns; it is 5°C outside. The room heating is also off and the room keeps getting colder.

Which is the most appropriate first action?

1. Pour boiling water from the gas stove directly into the tank to restore the temperature
2. Cover the tank with a blanket, hold a hot-water bottle against the side to retain heat, and run a battery-powered air pump
3. Move the fish into warm bathwater in the bathtub
4. Do nothing and wait for power; plecos are tough so they will be fine

AnswerB. Cover the tank with a blanket, hold a hot-water bottle against the side to retain heat, and run a battery-powered air pump

ExplanationWhen the heater stops in an outage, tropical catfish become immobile in the cold, and with the filter off oxygen also runs short. The right response is to cover the tank with a blanket or foam, hold a hot-water bottle or bottles of warm water against the sides to warm it gradually, and supply oxygen with a battery-powered air pump. Pouring boiling water in kills fish with localized heat and sudden change. Bathwater is dangerous because of chlorine, temperature, and residues. Left alone the water keeps cooling, and even plecos die below 15°C. After power returns, recheck the heater, and if the water fell to 20°C or below, consult a fish-knowledgeable shop right away.

IssuesThere was no preparation for a winter outage; no battery air pump or insulation was on hand. The owner did not realize how fast the temperature plunges once the heater stops.

ImprovementKeep a battery-powered air pump, foam board, hot-water bottle, and disposable hand warmers near the tank. Write the outage procedure on paper and post it. Use a digital thermometer that can be read during an outage.

A redtail catfish bought 3 years ago at 10 cm now exceeds 90 cm and cannot even turn around in its 120 cm tank. A move means you can no longer keep it, and the family says releasing it in the nearby river would return it to nature. You searched online for someone to take it but found no one, and the move is only 2 weeks away.

Which is the most appropriate decision?

1. Release it in the river; even a South American fish can survive in a warm river
2. Release it in a pond; it is fine if no one sees
3. Understand that release is illegal and ask the shop, a rehoming service, an aquarium, or a specialist group to take it
4. Cut back food to stop its growth and keep it in the current tank

AnswerC. Understand that release is illegal and ask the shop, a rehoming service, an aquarium, or a specialist group to take it

ExplanationReleasing non-native fish destroys ecosystems and is banned under the Invasive Alien Species Act and local ordinances, and abandoning a kept animal violates the Act on Welfare and Management of Animals. The fish often dies in the Japanese winter, so release is also cruelty. The right choice is to consult the shop, a rehoming service, an aquarium, or a specialist group to find a taker, and never choose release however long it takes. A pond is as illegal as a river, regardless of whether anyone is watching. Starving it to stop growth leads to starvation and disease, and keeping it in a tank where it cannot turn around is abuse. Research maximum size and lifespan before buying and commit to lifelong care.

IssuesThe owner did not check at purchase that the species exceeds 1 m and lives over 20 years, and made no plans for life changes such as moving. The family lacked awareness that release is illegal and harms the ecosystem.

ImprovementBefore buying a large fish, confirm maximum size, lifespan, and required tank size, and do not buy if you cannot keep it for life. Line up the shop or a taker while you are still keeping it. Make sure the family understands that release is illegal.

A 120 cm tank (about 250 kg of water) has sat on a cheap retail storage cube for a year. One night the stand creaks, the tank tilts forward, and water is seeping out. Inside are one redtail catfish and two large plecos. The floor is tatami and already damp. You are home alone, and the fish are calm on the bottom as usual.

Which is the most appropriate first action?

1. Lift the tank with the fish inside and move it somewhere else
2. Drain 1/3 of the water to reduce the load, move the fish with tank water into a large container with aeration, and replace the stand
3. Prop up the tilt with a board as a stopgap and wait until tomorrow
4. Empty the tank and keep the fish in the bathtub

AnswerB. Drain 1/3 of the water to reduce the load, move the fish with tank water into a large container with aeration, and replace the stand

ExplanationA large tank weighs several hundred kilograms in water alone, and a stand without the load rating collapses. First drain 1/3 of the water to reduce the load, move the fish with tank water into a large lidded container with aeration, empty the tank, and set it up again on a proper rated stand with a reinforced floor. Lifting the tank with fish inside can crack it and injure both fish and people. A stopgap fix left overnight can collapse, flooding the room and killing the fish. The bathtub is dangerous because of chlorine, temperature difference, and detergent residue. The moved fish will puncture bags or thin containers with their spines, so use a thick container, keep it dark and quiet.

IssuesThe owner did not understand the weight of a large tank and put it on an unrated storage cube on tatami. The creaking warning may have been ignored for a year, and no emergency evacuation container was prepared.

ImprovementPut large tanks on a dedicated aquarium stand and check and reinforce the floor's load capacity. Keep a large container that can hold the fish with water and a battery-powered air pump. Inspect the stand for warping and the tank rim for damage monthly.

Late at night, a family member getting up for the bathroom stepped on something in the dark hallway and screamed. A Japanese catfish (30 cm) had jumped out of the tank, and its pectoral spine is stuck in the person's sole, which is bleeding. The catfish is thrashing violently on the floor and its skin is starting to dry. The tank lid was half off.

Which is the most appropriate first action?

1. Rinse the person's wound under running water and stop the bleeding, while picking up the fish with wet hands, returning it to the tank, and increasing aeration
2. Put the fish first, grabbing it with a dry towel to return it to the tank
3. A thrashing fish is dangerous, so leave it until it stops moving and treat the person first
4. Kick the fish into the corner of the hallway and take the person to the hospital

AnswerA. Rinse the person's wound under running water and stop the bleeding, while picking up the fish with wet hands, returning it to the tank, and increasing aeration

ExplanationFor the person's puncture, rinse under running water, squeeze out a little blood, disinfect, and stop the bleeding. At the same time pick up the fish with wet hands, return it to the tank, and increase aeration, saving both in parallel. A dry towel strips the fish's slime coat and the spines catch in the cloth. Leaving it until it stops moving dries and kills the fish, and the thrashing spines damage the floor and people. Kicking seriously injures the fish. Spine wounds easily pick up tank bacteria; if swelling, throbbing pain, or spreading redness occurs, see a doctor the same day and mention a fish spine from an aquarium. Watch the fish for several days for cotton-like growth or red spots.

IssuesThe tank of a nocturnal, jump-prone fish had a lid gap and no weight. The family did not know the spines were dangerous, and the tank sat on a path walked barefoot at night.

ImprovementClose the lid with no gaps, weight it down, and plug cable holes. Move the tank away from the route to the hallway or bedrooms. Tell the whole family about catfish spines and what to do if one jumps out (pick it up with wet hands), and install a night light in the hallway.

You have been using a canister filter without a sponge on the intake. In the evening a cory catfish is pinned belly-first to the intake and cannot move. Its gills are working, but when you try to free it the current pulls it back on. Its underside looks like it is starting to turn red.

Which is the most appropriate first action?

1. Pinch the fish with your fingers and pull it off by force
2. Switch off the filter, free the fish once the flow stops, then isolate and observe it
3. Point the intake upward and wait for the fish to drop off naturally
4. Turn the filter to high so the flow blows the fish off

AnswerB. Switch off the filter, free the fish once the flow stops, then isolate and observe it

ExplanationWhen a small fish is pinned by strong suction at the intake, its belly and slime coat are damaged and the pressure causes breathing difficulty. First switch off the filter to stop the suction, let the fish come free on its own or gently release it, and watch for injuries in an isolation container. Pulling with fingers while the filter runs tears the skin under suction. Pointing the intake up does not stop suction. High flow widens the injury. After release, fit a sponge cover on the intake before restarting. If the isolated fish shows belly redness, cotton-like growth, or rolls over, consult a fish-knowledgeable shop or vet the same day.

IssuesThe owner ran a strong-suction filter without a sponge cover around small bottom dwellers. They did not know weakened fish are the ones that get stuck, and may have missed early signs of illness.

ImprovementAlways fit a sponge cover on the intake and avoid pairing small fish with strong flow. A fish that gets stuck is also a sign of poor health, so test the water and check the other fish.

The redtail catfish (80 cm) in a 150 cm tank gulped down bottom gravel and the heater's suction cup along with its food. Since then its belly is unnaturally swollen, it tries to regurgitate but nothing comes out, and it lists on the bottom. After 2 days there is no waste, and this morning it does not react even to its favorite frozen fish.

Which is the most appropriate response?

1. Reach into its mouth and pull out the foreign objects
2. Stop feeding, take photos and video, and phone a vet who sees large fish the same day
3. Feed oily food as a laxative to pass it
4. Massage the belly to push the objects into the intestine

AnswerB. Stop feeding, take photos and video, and phone a vet who sees large fish the same day

ExplanationLarge catfish gulp down anything in front of them, and gravel or equipment parts lodged in the gut cause a fatal blockage. Abdominal swelling, inability to regurgitate, and no waste are signs of blockage; stop feeding, take photos and video, and consult a vet who sees large fish the same day. Reaching into the mouth gets you bitten and seriously injured by spines and teeth, and damages the fish's esophagus. Oily food worsens the blockage and fouls the water. Massaging the belly damages the organs and the spines injure the owner. To prevent recurrence, go bare-bottom and move small items and heater parts out of the fish's reach.

IssuesThe owner did not know large catfish swallow substrate and equipment whole, laid gravel, and put a suction-cup heater within the fish's reach. They had not identified a vet who sees large fish.

ImprovementKeep large catfish in a bare-bottom tank and protect heaters and sensors with guards or run them externally. Feed directly with tongs or a feeding stick, away from equipment. Find a vet who can treat large fish in advance.

On a summer night a family member sprayed insecticide widely in the room with the tank because of mosquitoes. Room air is drawn in through the lid gap and the aeration. Thirty minutes later the cory catfish are breathing hard at the surface and the pleco has rolled over. The smell of the chemical still lingers in the room.

Which is the most appropriate first action?

1. Open the windows to ventilate, do a 1/3–1/2 water change with same-temperature dechlorinated water, add activated carbon, and increase aeration
2. Take the fish out and move them to a bucket of tap water in another room
3. Stop the filter to stop drawing in air
4. The chemical will break down with time, so observe without changing water

AnswerA. Open the windows to ventilate, do a 1/3–1/2 water change with same-temperature dechlorinated water, add activated carbon, and increase aeration

ExplanationInsecticide ingredients are highly toxic to fish and dissolve into the water via aeration and the surface. First ventilate to clear the chemical from the air, do a 1/3–1/2 water change with same-temperature dechlorinated water, put activated carbon in the filter to adsorb the chemical, and increase aeration. Tap water in a bucket is dangerous for weakened fish because of chlorine and temperature difference, and moving large species is itself a burden. Stopping the filter causes oxygen shortage and ammonia buildup. Doing nothing lets the poisoning progress to death. If rolling or breathing difficulty continues after the change, repeat a 1/3 change the next day, and consult a fish-knowledgeable shop or vet if there is no improvement.

IssuesThe family did not know insecticide in the tank room poisons fish. There was no sign on the tank banning insecticide, and no emergency supplies such as activated carbon were on hand.

ImprovementDo not use insecticide, mosquito coils, air fresheners, or deodorant sprays in the tank room, and tell the family. If use is unavoidable, cover the tank with plastic and pause aeration. Keep activated carbon on hand and store prepared water for changes.

While cleaning the canister filter on a 60 cm tank, you washed the media and hoses thoroughly with dish detergent, rinsed lightly with water, and put them back. The next morning fine bubbles linger on the surface, all the cory catfish are surfacing or lying down, and the pleco clings limply to the driftwood.

Which is the most appropriate first action?

1. Skim the bubbles off with a net and watch
2. Wash the media again with detergent to get it completely clean
3. Remove the detergent-contaminated media, do a 1/2 water change with same-temperature dechlorinated water, increase aeration, and replace with media rinsed in tank water
4. Add salt to help the fish recover

AnswerC. Remove the detergent-contaminated media, do a 1/2 water change with same-temperature dechlorinated water, increase aeration, and replace with media rinsed in tank water

ExplanationEven a trace of dish detergent damages fish gills and slime coat and wipes out the filter bacteria. Remove the media with detergent residue, do a 1/2 water change with same-temperature dechlorinated water to dilute the chemical, and increase aeration. Media should only be rinsed lightly in tank water, never with detergent. Skimming bubbles leaves the detergent in the water. Washing again with detergent makes it worse. Salt burdens catfish and does not remove the cause. Watch for foaming and the fish's breathing for several days after the change and do another 1/3 change the next day. Isolate any fish still rolling, and consult a fish-knowledgeable shop or vet if there is no improvement.

IssuesThe owner did not know the basic rule that media is only rinsed lightly in tank water, and used detergent. They did not understand that detergent kills bacteria and fish alike.

ImprovementRinse media lightly by squeezing in tank water during a water change and never replace it all at once. Never use detergent on aquarium equipment; keep a dedicated bucket and sponge. Post the equipment-cleaning method near the tank and share it with the family.

An August afternoon; with the air conditioning off while you were out, the water in a 90 cm tank reached 33°C. On returning, the pleco has rolled over and the cory catfish are breathing hard at the surface. The water is a little cloudy and the filter is running normally. There is no aeration, and the room is over 35°C.

Which is the most appropriate first action?

1. Pour in a large amount of refrigerator-cold water to drop it to 25°C at once
2. Turn on the air conditioning, set aeration to maximum, do a 1/3 change with dechlorinated water slightly cooler than the tank, and turn off the lights
3. Float ice directly in the tank
4. Take the fish out and move them to cold water in a cooler

AnswerB. Turn on the air conditioning, set aeration to maximum, do a 1/3 change with dechlorinated water slightly cooler than the tank, and turn off the lights

ExplanationWater at 33°C holds less oxygen and raises catfish metabolism, leading to suffocation and poisoning. Cool the room with air conditioning, set aeration to maximum, do a 1/3 change with dechlorinated water 2–3°C cooler than the tank to lower it gradually, and turn off the lights. The rule is no more than 2°C change per day; dumping in cold water or ice causes temperature shock that kills weakened fish. Cold water in a cooler is an even more sudden change. Do not isolate the rolled-over pleco; darken the tank and watch for 30 minutes to see if breathing stabilizes, and consult a fish-knowledgeable shop or vet if it does not improve.

IssuesThe owner turned off the air conditioning while out in midsummer, had no cooling equipment, and let the water reach 33°C. They did not know high temperature causes oxygen shortage, and aeration was lacking.

ImprovementRun the air conditioning continuously in summer or install a cooling fan or chiller to stay at or below 28°C. Run aeration year-round. Use a digital thermometer and consider one you can check remotely.

A strong (intensity 5) earthquake spilled half the water from a 120 cm tank, and the driftwood toppled onto the pleco, pinning it. The power is out, so filter and heater have stopped, and the floor is flooded. The redtail is thrashing in the remaining water. The family is safe, and aftershocks continue.

Which is the most appropriate first action?

1. First secure your own and your family's safety, then gently free the driftwood underwater, top up with dechlorinated water, and run a battery-powered air pump
2. Immediately put your hands in the tank to hold the redtail and calm it
3. Take all the fish out and bring them to the evacuation shelter
4. Adding water will just spill again in an aftershock, so leave it as is

AnswerA. First secure your own and your family's safety, then gently free the driftwood underwater, top up with dechlorinated water, and run a battery-powered air pump

ExplanationIn a disaster, secure people's safety first, check for broken glass and submerged outlets, and only then deal with the tank. Free the driftwood gently underwater, top up with dechlorinated water to restore the level, and supply oxygen with a battery-powered air pump. Holding a thrashing redtail bare-handed causes serious injury from spines and bites. Bringing a large fish to a shelter is not realistic; if you evacuate, insulate and aerate at home and do not feed until you return. Without topping up, oxygen shortage and rising ammonia kill the fish. After freeing the pinned pleco, isolate it, and seek advice if it has wounds or rolls over.

IssuesNo earthquake precautions had been taken: the tank and lid were not secured and the water level was not kept lower. No battery air pump or stored dechlorinated water was on hand for an outage.

ImprovementAnchor the stand to the wall and put anti-slip earthquake mats under the tank. Build driftwood low and secure it. Keep a battery-powered air pump, dechlorinator, and stored water, and share the outage procedure with the family.

A 5-hour drive for a move in February. You must transport a sailfin pleco (35 cm) and 6 cory catfish from a 90 cm tank. You fed them as usual up to the day before. You only have thin plastic bags, and it is 3°C outside. Departure is 8 a.m. with two rest stops planned, and the tank at the new home is not yet set up.

Which is the most appropriate transport preparation?

1. Stop feeding the day before, put the pleco in a thick lidded container and the corys in oxygen-filled double bags, insulate in a foam box, and keep dark
2. Feed well on the morning of departure, put everyone in one thin bag, and place it in front of the car heater
3. Leave the tank half full with the fish inside and drive it
4. Thin bags are fine, so add plenty of water and load them in the trunk

AnswerA. Stop feeding the day before, put the pleco in a thick lidded container and the corys in oxygen-filled double bags, insulate in a foam box, and keep dark

ExplanationWaste during transport fouls the water, so stop feeding 2 days beforehand. Pleco spines tear thin bags, so put it with tank water in a thick lidded container; put the corys in oxygen-filled double bags; place everything in a foam box for insulation, keep it dark, and drive gently. Feeding on the day fouls the water and causes poisoning. Everyone in one bag means the spines tear it, and the heater vent causes a dangerous temperature spike. Driving a tank with water in it risks cracks and leaks and the fish are injured by sloshing. The trunk is cold in winter and hot in summer. On arrival, acclimate the fish and hold off feeding until they settle.

IssuesThe owner had not prepared thick transport containers, oxygen, or a foam box, and kept feeding until the day before. They did not realize catfish spines tear bags or how important insulation is in winter.

ImprovementOnce a move is decided, gather transport supplies (thick containers, foam box, oxygen can, hand warmers) 2 weeks ahead. Stop feeding 2 days before. Move the tank empty, set it up with new water on arrival, and acclimate the fish before adding them.

Into a newly set up 60 cm tank, you added 10 cory catfish and 2 plecos all at once after one week. From day 3 they went still on the bottom one by one, and this morning two were dead. The water is clear, but the remaining fish are moving their gills fast and gathering near the surface. A test strip shows high ammonia.

Which is the most appropriate first action?

1. Add fish medication to prevent infection
2. Replace the filter with a new one to clean the water
3. Leave the dead fish and feed the survivors more to build their strength
4. Remove the bodies, do a 1/3 water change daily with same-temperature dechlorinated water, cut feeding, and spread the fish out

AnswerD. Remove the bodies, do a 1/3 water change daily with same-temperature dechlorinated water, cut feeding, and spread the fish out

ExplanationA freshly set up tank has no established filter bacteria, and adding many fish at once sends ammonia soaring and poisons them. Dead bodies rot and worsen the water further, so remove them immediately, do a 1/3 water change daily with same-temperature dechlorinated water, cut feeding, and if possible spread the fish into separate containers. Fish medication targets infections, which are not the cause, and hinders bacteria from establishing. A new filter loses what few bacteria exist. More food means more ammonia. Toxicity is invisible even in clear water, so test daily until the readings fall, and if fish keep weakening consult a shop or vet the same day.

IssuesThe owner added 12 fish at once before the filter was cycled, ignoring catfish waste output and the tank's processing capacity. They judged safety by clear water and only started measuring ammonia after fish died.

ImprovementAfter setup, start with a few hardy fish and add more gradually over 2–4 weeks. Test ammonia and nitrite daily and add fish only after consistent zero readings. Seeding with media from an established tank speeds cycling.

You keep a Japanese catfish (40 cm) in a large outdoor plastic tub. Prolonged rainy-season rain overflowed the tub and washed in leaves and mud. A week later a white, mucus-like film is spreading on the catfish's back and there are red spots at the fin bases. It responds poorly to food and often floats near the surface.

Which is the most appropriate first action?

1. Rub off the white film by hand and watch, leaving the muddy water
2. Replace all the water to reset the environment
3. Remove the mud and leaves, do a 1/3 change with same-temperature water, set up aeration, take photos, and seek advice
4. Lower the water level and raise the temperature to give it a sunbath

AnswerC. Remove the mud and leaves, do a 1/3 change with same-temperature water, set up aeration, take photos, and seek advice

ExplanationWater fouled with mud and rotting leaves breeds bacteria and parasites; a white film on the body signals excess mucus or parasites, and red spots signal bacterial infection. Remove the mud and leaves, do a 1/3 change with same-temperature water, set up aeration to add oxygen, photograph the symptoms, and consult a fish-knowledgeable shop or vet the same day. Rubbing by hand strips the slime coat and spreads infection. A full water change kills a weakened fish with sudden pH and temperature swings. Lowering the level and raising the temperature causes oxygen shortage and bacterial growth. An outdoor tub needs a lid and an overflow drain to keep rainwater out.

IssuesThe outdoor setup had no protection against rainwater, and the mud and leaves were left for a week. There was no aeration, and inspections were too infrequent for rainy-season water deterioration.

ImprovementFit outdoor tubs with a lid, rain cover, and overflow outlet. After heavy rain always check for cloudiness and the fish's condition, and do a 1/3 change by the next day if fouled. Install permanent aeration.

You keep 3 bristlenose plecos in a 90 cm tank. For 3 days the plecos have been rubbing hard against the driftwood, and a thin, cloudy white film has appeared on their skin. No white spots are visible. You recently bought live bloodworms from a shop and fed them. Water is 26°C and no nitrite is detected.

Which is the most appropriate response?

1. No white spots means parasites are unlikely; just change water and watch
2. Add double the labeled dose of salt to shed the parasites
3. They have few scales so medication cannot be used; nothing can be done, so leave it
4. Stop live food, do a 1/3 change, take video and seek advice, and run any medicated bath in a separate container starting at half dose

AnswerD. Stop live food, do a 1/3 change, take video and seek advice, and run any medicated bath in a separate container starting at half dose

ExplanationEven without white spots, rubbing and cloudy slime point to irritation from microscopic skin parasites or bacteria brought in with live food. Stop the live food, do a 1/3 water change to reduce parasites in the water, take video, and consult a fish-knowledgeable shop or vet. If a medicated bath is needed, run it in a separate container starting at half the labeled dose, and dilute with a water change if breathing becomes labored. Scaleless plecos are sensitive to medication but can be treated when it is used properly; leaving it only makes things worse. Double-dose salt puts heavy osmotic stress on catfish and can kill. Water changes alone cannot eradicate parasites, which spread to other fish.

IssuesThe owner fed live food without quarantine and lacked the knowledge to prevent parasite introduction. They assumed no white spots meant no parasites and had not confirmed in advance how to medicate catfish.

ImprovementSwitch to frozen or prepared food; if live food is used, rinse well in tank water and hold it in a separate container for a few days. Confirm with the shop how to run medicated baths for catfish and plecos, and keep a separate container and aeration ready. Record video immediately when rubbing appears.

December; you keep a sailfin pleco (20 cm) in a 60 cm tank with no heater. Room temperature falls to 10°C at night and the thermometer reads 14°C. The pleco has not eaten tablets for over a week and sits motionless in the shade of the driftwood. Its skin looks normal and water quality is fine.

Which is the most appropriate response?

1. The cause is low temperature; install a heater and raise it 1–2°C per day to 25–27°C
2. It has gone into hibernation, so stop feeding and leave it until spring
3. Appetite has dropped, so treat with fish medication
4. Not moving means disease, so quickly raise the temperature to 30°C

AnswerA. The cause is low temperature; install a heater and raise it 1–2°C per day to 25–27°C

ExplanationPlecos are South American tropical fish and do not hibernate; at 14°C digestion and metabolism shut down, they cannot eat, and they weaken. Install a heater and raise the temperature 1–2°C per day to 25–27°C. Mistaking this for hibernation and leaving it until spring leads to starvation, or low immunity in the cold brings fungus and bacterial infection. With normal skin and water, medication is unnecessary and only a burden. Jumping to 30°C causes fatal temperature shock. If it still does not eat several days after warming, check for a sunken belly and consult a fish-knowledgeable shop or vet. It is important to understand the difference between the native Japanese catfish and tropical plecos.

IssuesThe owner kept a tropical pleco without a heater and let winter temperatures fall. Even after more than a week without eating they did not recognize temperature as the cause and nearly acted on the false belief in hibernation.

ImprovementKeep plecos, corys, and redtails at 25–27°C year-round with a heater. Have a thermostat and spare heater, and check the temperature every morning. Decide in advance to act immediately if the water falls below 20°C in case of heater failure.

At night, a child in the tank room screamed, startled by fireworks. The redtail catfish (70 cm) in a 150 cm tank panicked and crashed into the glass; its upper lip is split and bleeding. It is still thrashing in agitation in a corner, and part of a barbel is broken.

Which is the most appropriate first action?

1. Put your hand in and press on the mouth wound to stop the bleeding
2. Take the fish out and press a dry cloth on it to stop the bleeding
3. Slap the surface to drive the fish to the bottom until it calms down
4. Turn off the lights, keep quiet, do not touch the wound, keep the water clean, and wait for the bleeding to stop

AnswerD. Turn off the lights, keep quiet, do not touch the wound, keep the water clean, and wait for the bleeding to stop

ExplanationLarge catfish are sensitive to sound and vibration and injure their mouths and barbels crashing when startled. A fish's bleeding cannot be pressed on underwater, and putting your hand in with an agitated large fish gets you hurt by spines and bites. Turn off the lights to reduce stimulation, leave the wound alone, and keep the water clean; a small laceration stops bleeding on its own. Taking it out and pressing with cloth strips the slime coat, and drying plus thrashing widen the wound. Slapping the surface agitates it further and causes another crash. Watch the wound for several days; if cotton-like growth or red spots spread or it stops eating, consult a vet who sees large fish the same day. Barbels regrow gradually in a clean environment.

IssuesThe family did not understand that large catfish crash when startled by sound and vibration, and shouted in the tank room. There was little driftwood or shelter to cushion the glass, leaving no escape.

ImprovementPlace the tank where there is little foot traffic or loud noise, and explain to the family why quiet matters. Provide a large shelter the fish can hide in, and dim the lights in stages at night. Cover the tank with cloth during fireworks or thunder.

While moving 8 cory catfish to a bucket for a tank reset, one got tangled in the net and you yanked it free in a panic. Back in the tank, that fish's dorsal spine is broken at the base and bent, and the base is red and swollen. It can swim but mostly sits still on the bottom.

Which is the most appropriate response?

1. Trim the broken spine with scissors to tidy it
2. Push the bent spine back into position by hand
3. Keep it in an isolation container with clean water at a stable temperature, check the wound daily, and seek advice if cotton-like growth appears
4. The spine wound is small, so do nothing and return it to the community tank

AnswerC. Keep it in an isolation container with clean water at a stable temperature, check the wound daily, and seek advice if cotton-like growth appears

ExplanationThe base of a broken spine bleeds and swells and becomes an entry point for fungus and bacteria. Keep it in an isolation container with clean water at 25–27°C, check the wound daily, and consult a fish-knowledgeable shop or vet the same day if cotton-like growth or red spots spread. Cutting the spine creates a new wound and damages tissue with nerves and blood vessels. Pushing it back tears it further. In the community tank other fish peck at it and unstable water slows healing. A broken spine does not grow back, but once healed it does not affect daily life. The net was the cause, so from now on scoop with water in a container.

IssuesThe owner used a net on a catfish and yanked in a panic when it tangled. They did not know the infection risk after a broken spine and had no criteria for isolation. No isolation container was prepared.

ImprovementMove cory catfish by scooping them with water in a plastic cup or bowl. If using a net, use fine vinyl mesh and cut it underwater with scissors if tangled. Keep an isolation container, aeration, and dechlorinator on hand and isolate immediately on injury.

You tried to peel a pleco (25 cm) off the glass by hand for cleaning. When you pulled hard the edge of its mouth split, and the area around the mouth is red and swollen. Since then the pleco cannot attach to the driftwood and lies on its side on the bottom. It does not respond to food.

Which is the most appropriate response?

1. Apply human ointment to the mouth wound and return it to the tank
2. Skip cleaning the glass and clean it once the pleco recovers
3. Keep it in an isolation container with clean water, place soft food nearby, and seek advice the same day if it does not eat for several days
4. Lying on its side is swim bladder disorder, so add fish medication

AnswerC. Keep it in an isolation container with clean water, place soft food nearby, and seek advice the same day if it does not eat for several days

ExplanationA pleco's sucker mouth is delicate, and forcing it off while attached splits the mouth edge. A mouth wound prevents both feeding and attaching and is an entry point for infection. Keep it in an isolation container with clean water at a stable temperature, place soft boiled vegetables or soaked tablets by its mouth, and check whether it can eat. If it cannot eat for several days, consult a fish-knowledgeable shop or vet the same day. Human ointment is toxic to fish and fouls the water. Lying on its side is from mouth pain and exhaustion, not swim bladder disorder; medication only adds stress. To move an attached pleco, stop the flow and wait for it to let go, or lift it gently underwater from the tail end.

IssuesThe owner did not know how the sucker mouth works and forced the attached pleco off. They had not thought in advance about how to move the fish for cleaning and did not recognize the risk of injuring it.

ImprovementDo not move the fish while cleaning; work around the area it is attached to. If it must be moved, stop the flow and wait for it to let go on its own. Keep soft pleco food and an isolation container on hand and isolate immediately if the mouth is abnormal.

The rockwork in a 90 cm tank collapsed and the pleco (30 cm) is pinned under a rock. Only the tail fin is visible, and it is moving. The rock is heavy, and lifting it by hand risks pressing on the fish even more. The other fish are startled and gathered in a corner, and the water is slightly cloudy.

Which is the most appropriate first action?

1. Pull the fish out by the tail
2. Lift the rock gently with both hands underwater, and once the fish comes out on its own, isolate it and check for injuries
3. Drain all the water first so the rock can be taken out of the tank
4. Wait several hours for the fish to free itself

AnswerB. Lift the rock gently with both hands underwater, and once the fish comes out on its own, isolate it and check for injuries

ExplanationPulling a pinned fish by the tail catches the spines on the rock and tears their bases, causing serious injury. Lift the rock gently with both hands underwater, wait for the fish to come out on its own, then keep it in an isolation container with clean water and watch for several days for internal bleeding from crushing or skin wounds. Draining the water dries the fish and the crushing continues during the work. Waiting hours lets organ damage and suffocation progress. After isolation, if it rolls over, the belly reddens, or it keeps refusing food, consult a fish-knowledgeable shop or vet the same day. Secure rockwork with adhesive or a base and leave no gaps a pleco can burrow under and topple.

IssuesThe rocks were stacked unsecured, without considering that a pleco could burrow under and topple them. There was no procedure for moving heavy rocks safely underwater and no isolation container for an injured fish.

ImprovementSecure rockwork with aquarium-safe adhesive and set it directly on the tank bottom so there are no gaps for fish to burrow under. Keep heavy items away from the tank walls. Keep an isolation container and aeration on hand.

At night, the power strip sitting on top of the tank shifted with vibration and fell into the water. The heater and filter are plugged into it, and the strip is submerged. The fish are moving on the bottom, but bubbles are rising at the surface. You stopped a family member who was about to grab it with wet hands.

Which is the most appropriate first action?

1. Quickly reach in and pull the strip out
2. Put on dry rubber gloves and lift the strip out
3. Take the fish out first, then cut the power
4. Unplug at the wall outlet or cut the breaker, then remove the strip and check the fish and aeration

AnswerD. Unplug at the wall outlet or cut the breaker, then remove the strip and check the fish and aeration

ExplanationA live power strip underwater is an electrocution hazard; before any hand goes in, the top priority is unplugging at the wall or cutting the breaker. Once power is off, remove the strip, check the fish and whether the filter and heater work, and run a battery-powered air pump in place of any stopped equipment. Rubber gloves still conduct when wet, and taking the fish out first also means putting your hands in, which is dangerous. Fish may have died from electrocution, but if they are moving, watch for recovery. Replace the equipment because of leakage risk, and mount the strip higher than the tank, fixed to the wall where it cannot fall.

IssuesThe owner put the power strip on top of the tank without considering that vibration could knock it in. They lacked electrical safety knowledge, and a family member tried to grab the strip with wet hands.

ImprovementFix the power strip to the wall above the tank, and route cords with a drip loop so water cannot run down them. Use a strip with a ground-fault breaker. Tell the family the rule of never touching electrical devices in water.

While feeding the redtail catfish (80 cm) in a 150 cm tank, the moment your fingers entered the water your whole hand was sucked in and bitten. The inside of its mouth is lined with rasp-like teeth; pulling back drives the bite deeper, and the skin is scraped and bleeding. The fish keeps its mouth shut and will not let go.

Which is the most appropriate first action?

1. Yank your hand out by force
2. Hit the fish on the head to make it open its mouth
3. Lift the fish out of the water to open its mouth
4. Stop moving, wait for the fish to open its mouth, and gently withdraw your hand underwater

AnswerD. Stop moving, wait for the fish to open its mouth, and gently withdraw your hand underwater

ExplanationA redtail mistakes a hand for food and tries to swallow it whole, scraping the skin with rasp-like teeth. Pulling by force tears off a large patch of skin and splits the fish's mouth. The right response is to stop moving, wait for the fish to open its mouth, and gently withdraw your hand underwater. Hitting the head makes the fish thrash, deepens the bite, and drives spines in. Lifting it out of the water causes violent thrashing and serious injury to both owner and fish. After release, rinse the wound under running water and disinfect; if swelling, throbbing pain, or fever develops, see a doctor the same day and say you were bitten by an aquarium fish. Always feed with a feeding stick or tongs and keep fingers out of the water.

IssuesThe owner underestimated a large catfish's suction and teeth and fed it bare-handed. They did not use tools like a feeding stick and did not know what to do when bitten.

ImprovementFeed large catfish with a long feeding stick or tongs, and for any work that puts hands in the water, confine the fish behind a divider first. Share with the family that when bitten you stay still and wait, and keep a first-aid kit near the tank.

After a move you temporarily housed a redtail (50 cm) with 5 cory catfish in a 90 cm tank. The next morning only 2 corys remain, and the redtail is drifting near the surface in distress with its mouth half open. Something appears to be lodged at the back of its mouth.

Which is the most appropriate first action?

1. A cory's spines may be lodged in its throat; take photos and video and contact a vet who sees large fish right now
2. Reach into the back of its mouth and pull the lodged fish out
3. Give the redtail another food item to push it down
4. It will digest with time, so watch and wait

AnswerA. A cory's spines may be lodged in its throat; take photos and video and contact a vet who sees large fish right now

ExplanationWhen swallowed, a cory spreads its pectoral spines and lodges in the predator's throat, often killing both. A redtail in distress with its mouth half open likely has spines stuck in its throat; take photos and video and phone a vet who sees large fish right now. Reaching into the mouth gets you bitten and breaks the spines off in the throat. Another food item cannot push spines down and widens the wound. Left alone it dies from suffocation or infection. Move the remaining corys to a separate container immediately. Even temporarily, never house fish that fit in another's mouth together; keep a divider or small spare tank ready.

IssuesThe owner housed bite-sized corys with a large catfish because it was only temporary. They did not know cory spines lodge in a predator's throat and had no spare containers ready for the move.

ImprovementNever house large catfish with small fish, even temporarily. For moves or tank resets, prepare enough spare containers for everyone plus a divider. Confirm the contact details of a vet who sees large fish in advance.

You keep 2 Japanese catfish in a large plastic tub in the garden. The day after the neighbor sprayed pesticide on their field, rain fell; now an oily film floats on the surface, the catfish are gasping at the surface and listing. There is no lid, so rainwater runs straight in. There is no aeration, and the water smells chemical.

Which is the most appropriate first action?

1. Blot up the oily film with paper towels and watch
2. Replace more than half the water, add activated carbon and aeration, and fit a lid to prevent further inflow
3. Release the fish into the river to recover in clean water
4. Add salt to help the fish detoxify

AnswerB. Replace more than half the water, add activated carbon and aeration, and fit a lid to prevent further inflow

ExplanationPesticides are highly toxic to fish; the surface film, breathing difficulty, and listing are signs of poisoning. Replace more than half the water with same-temperature dechlorinated water to dilute the chemical, adsorb it with activated carbon, add oxygen with aeration, and fit a lid to keep rainwater out. Blotting the film leaves the chemical in the water. Releasing into the river disrupts local genetic lineages even for a native catfish, and releasing weakened fish counts as abandonment. Salt does not detoxify and only adds stress. Repeat a 1/3 change the next day, and consult a fish-knowledgeable shop or vet if listing continues. Ask the neighbor to tell you spraying dates in advance.

IssuesThe outdoor setup had no lid, so rainwater and surrounding chemicals ran straight in. The owner was unaware of the neighbor's spraying and had no activated carbon or stored water for changes.

ImprovementFit outdoor containers with a rain lid and overflow outlet. Check neighbors' spraying schedules and cover with plastic on spraying days. Keep activated carbon, stored water, and an air pump on hand, and always check the surface and the fish after rain.

For 2 months you have fed 6 cory catfish only goldfish floating flakes. Lately they gulp air every time they eat at the surface, and some then get a swollen belly and float, unable to sink to the bottom. Their barbels have shortened and they are getting thin overall. Water is 26°C, water quality is normal, and there are no white spots or red marks.

Which is the most appropriate response?

1. It is swim bladder disorder, so give a medicated bath
2. Press the belly of floating fish to release the air
3. Switch to sinking cory tablets or frozen bloodworms and feed on the bottom before lights-out
4. Feed even more to make up the nutritional deficit

AnswerC. Switch to sinking cory tablets or frozen bloodworms and feed on the bottom before lights-out

ExplanationCory catfish forage on the bottom; eating floating flakes at the surface makes them gulp air, gas builds up in the gut, and they float. They also go undernourished, get thin, and their barbels deteriorate. The right response is to switch to sinking cory tablets or frozen bloodworms and let them eat on the bottom before lights-out. Floating is from swallowed air, not swim bladder disorder; medication is unnecessary and stressful. Pressing the belly damages the organs and the spines injure the owner. More floating food still never reaches the bottom and worsens water quality and the floating. If floating continues several days after the switch, consult a fish-knowledgeable shop.

IssuesThe owner did not know bottom-dweller feeding habits and fed only goldfish floating food for 2 months. They missed multiple signs: air gulping, weight loss, and deteriorating barbels.

ImprovementFeed corys sinking tablets or frozen bloodworms before lights-out and confirm everyone is eating on the bottom. Check the right type of food with the shop at purchase. Check belly fullness and barbel length weekly.

September; a major typhoon is forecast to hit tomorrow. You keep one redtail in a 150 cm tank and plecos and corys in a 90 cm tank, and the outage could last a full day. It is 28°C outside. You are considering what you can do tonight. Both tanks rely solely on mains-powered filtration and aeration, and the fish are healthy for now.

Which is the most appropriate preparation tonight?

1. Feed generously, enough to cover tomorrow too
2. Turn off the heater and filter tonight to get the fish used to the outage
3. Replace all the water to make it clean
4. Stop feeding, prepare a battery-powered air pump with batteries, stored dechlorinated water, and foam insulation, and do a 1/3 water change

AnswerD. Stop feeding, prepare a battery-powered air pump with batteries, stored dechlorinated water, and foam insulation, and do a 1/3 water change

ExplanationDuring an outage filtration and aeration stop, and the heavy waste of catfish fouls the water fast. Stop feeding to reduce waste, prepare a battery-powered air pump with spare batteries, stored dechlorinated water, and insulation such as foam, and do a 1/3 water change the day before to improve water quality. Generous feeding sends ammonia soaring during the outage. Shutting equipment off tonight is pointless and harms the filter bacteria. A full water change loses bacteria and destabilizes the water. During the outage run the battery air pump, cover with foam if the temperature drops, and after power returns test the water before resuming feeding.

IssuesThe owner had not thought about outage preparation until the day before the typhoon and had no battery air pump or stored water on hand. They were not aware that large fish's waste output raises the risk during an outage.

ImprovementKeep a battery-powered air pump and batteries, dechlorinator, a jerry can for stored water, and foam insulation on hand. When a disaster is forecast, change water and stop feeding the day before. Write the outage procedure on paper and post it near the tank.

Late on a January night, the thermostat heater fails and the water in a 90 cm tank has dropped to 18°C. The pleco and corys sit motionless on the bottom with slow gill movement. There is no spare heater and the pet shop is closed. The room is 8°C and the water keeps falling.

Which is the most appropriate first action?

1. Pour boiling water into the tank bit by bit to bring it back to 25°C
2. Take the fish out and put them in the bathtub water
3. Cover the tank with foam and a blanket, float bottles of hot water in the tank, heat the room, and raise it gradually
4. Put an electric heater close to the tank glass to warm it

AnswerC. Cover the tank with foam and a blanket, float bottles of hot water in the tank, heat the room, and raise it gradually

ExplanationTropical catfish whose water has fallen to 18°C from heater failure slow their metabolism and die below 15°C if left. Cover the tank with foam or a blanket to prevent heat loss, float bottles of hot water to warm it gently at about 1°C per hour, heat the room, and get a heater the next morning. Pouring in boiling water kills fish with localized heat and sudden change. Bathwater is dangerous because of chlorine, temperature difference, and detergent residue. An electric heater against the glass can crack it and is a fire risk. A change over 3°C per day from rapid warming causes temperature shock, so go carefully, and check water quality the next morning.

IssuesThere was no spare heater and no plan for a rapid temperature drop on a winter night. No emergency insulation or hot-water method was prepared, and the thermostat was not checked routinely.

ImprovementKeep a spare heater and thermostat, and split heating across two heaters to reduce failure risk. Check a digital thermometer every morning and keep foam and a hot-water bottle near the tank in winter. Replace heaters every 1–2 years.

With a hangnail on your hand, you cleaned the tank substrate and washed filter media bare-handed. Two weeks later a hard, reddish-purple lump formed at the base of your index finger, and a chain of small swellings is gradually spreading toward the wrist. The pain is mild, but over-the-counter ointment does not help.

Which is the most appropriate response?

1. Suspect a skin infection from the tank water, see a dermatologist, and mention the aquarium work
2. Keep using the over-the-counter ointment and wait
3. Lance the lump with a needle to drain the pus
4. Scrub the whole tank with disinfectant and dispose of all the fish

AnswerA. Suspect a skin infection from the tank water, see a dermatologist, and mention the aquarium work

ExplanationTank water and substrate harbor atypical mycobacteria, which enter through hand wounds and weeks later cause hard lumps that spread along the lymph vessels as a skin infection. Ordinary ointments do not cure it, and the aquarium history is key to diagnosis, so see a dermatologist and say you keep aquarium fish. Continuing ointment delays treatment, and lancing spreads the infection deeper. Scrubbing the tank or disposing of the fish is unnecessary; the bacteria are common in the environment, so prevention on the human side is what matters. From now on wear gloves when you have a hand wound and wash with soap after working.

IssuesThe owner worked in the tank bare-handed with a hand wound and did not know tank water harbors bacteria that cause skin infection. They self-treated with over-the-counter medicine and did not see a doctor until the lumps spread.

ImprovementWear waterproof gloves for aquarium work, without fail when you have a hand wound. Wash with soap and running water afterward. See a dermatologist early for any slow-healing skin problem after aquarium work and mention the fish-keeping history.

Your 2-year-old drank tank water with a cup from a bucket left on the floor during a water change. The bucket held substrate dirt and fish waste. From the next day the child has repeated vomiting and watery diarrhea with a fever of 38°C, is taking little fluid, and is becoming listless.

Which is the most appropriate response?

1. Give children's anti-diarrheal medicine and watch
2. Tank water is natural and harmless; this is not food poisoning
3. See a pediatrician, say the child drank aquarium water, and bring a photo of the stool
4. Judge the fish to be sick and treat them with fish medication

AnswerC. See a pediatrician, say the child drank aquarium water, and bring a photo of the stool

ExplanationAquarium water and substrate can contain bacteria such as Salmonella, and a toddler who drinks it can develop gastroenteritis. Vomiting, watery diarrhea, and fever are symptoms of bacterial enteritis, and dehydration progresses fast, so see a pediatrician the same day and report that the child drank tank water. Anti-diarrheals stop the bacteria from being cleared and make it worse. Dismissing it as harmless leads to dehydration and severe illness. The fish themselves are not sick; fish medication is irrelevant. Keep buckets out of children's reach during water changes, keep the child in another room, or finish quickly. Make sure the whole family washes hands after aquarium work.

IssuesA bucket of tank water was left on the floor within a toddler's reach during a water change. The owner did not know tank water can cause infection in people and was not watching the child during the work.

ImprovementDo water changes while the child naps or is in another room, and keep buckets up high or lidded. Everyone washes hands afterward. In homes with toddlers, fence off the tank area and teach them not to touch the water.

You keep cory catfish, plecos, and a Japanese catfish in three separate tanks. White spot disease (ich) broke out in the cory tank and is under treatment. The other two are healthy. You share the same net, bucket, and hose across all three, and use the same tweezers for daily feeding. After use, equipment is rinsed lightly with water and set aside.

Which is the most appropriate response?

1. Add medication to the other tanks as a precaution
2. Equipment can be shared without problem if rinsed lightly with water
3. Mix some water between the three tanks to build immunity
4. Keep separate equipment per tank; wash and fully dry anything that must be shared. Work on healthy tanks first

AnswerD. Keep separate equipment per tank; wash and fully dry anything that must be shared. Work on healthy tanks first

ExplanationIch parasites spread to other tanks via water droplets and equipment. Keep separate nets, buckets, hoses, and tweezers per tank, wash and fully dry anything shared before use, and work on healthy tanks first and the sick tank last. Precautionary medication puts needless stress on medication-sensitive catfish and harms the filter bacteria. A light rinse leaves parasites behind. Mixing water spreads the infection; fish cannot be expected to gain immunity. Keep equipment separate for 2 weeks after treatment and consider sharing only after the sick tank's fish have fully recovered. Wash your hands between tanks too.

IssuesThe owner shared equipment across tanks without considering how disease spreads between them. Basic hygiene knowledge such as work order and drying equipment was lacking.

ImprovementPrepare color-coded nets, buckets, and hoses per tank. Work in order from healthy tanks and wash hands at the end. Keep an isolation container on hand and separate equipment completely when disease appears.

Three cory catfish died in a 60 cm tank with symptoms that looked like Aeromonas infection. The remaining fish seem fine, but the bodies were left in the tank for a day. You are unsure how to dispose of the bodies and what to do with the remaining fish and the tank. The water is slightly cloudy and smells fishy.

Which is the most appropriate response?

1. Dump the bodies in the nearby river and disinfect the tank with chlorine bleach, fish included
2. Remove the bodies with gloves, bag and discard them, do a 1/3 water change, watch the remaining fish for several days, and wash and dry equipment
3. Leave the bodies in the tank as food for the other fish
4. Scrub the whole tank and replace the sand and filter media with new

AnswerB. Remove the bodies with gloves, bag and discard them, do a 1/3 water change, watch the remaining fish for several days, and wash and dry equipment

ExplanationDead bodies rot, rapidly foul the water, and breed bacteria, so remove them with gloves, bag them, and discard with burnable trash. Do a 1/3 water change to reduce organic matter, watch the remaining fish for several days, and isolate any that show symptoms. Wash and dry equipment. Dumping bodies in a river spreads pathogens into nature and is also illegal. Bleach in a tank with fish kills them. Leaving bodies as food spreads the infection. A full scrub and replacement loses the bacteria, and the water-quality crash kills the remaining fish. Aeromonas is triggered by poor water quality, so the root fix is to review water-change frequency and feeding amounts.

IssuesThe bodies were left for a day, inviting rot and bacterial spread. The owner lacked knowledge of proper disposal and tank disinfection and was torn between an extreme full replacement and doing nothing.

ImprovementCount the fish every morning after lights-on and remove any bodies as soon as found. Keep disposal gloves and bags near the tank. From setup, make weekly water changes and bottom cleaning a habit to prevent Aeromonas, and review feeding amounts.

In the morning you find a cory catfish dried out on the floor behind the tank. The slime on its skin has dried white, its fins are shriveled, and it does not move, but on close inspection the gill cover is moving slowly. The tank is at 26°C. The other fish are fine, and there is no aeration.

Which is the most appropriate first action?

1. A dried fish cannot be saved, so bury it
2. Return it to the tank with wet hands, hold its mouth into the current, add aeration, and watch for 30 minutes
3. Rub the dried body hard with a wet cloth to remove the slime
4. Return it to the tank and feed it right away to encourage recovery

AnswerB. Return it to the tank with wet hands, hold its mouth into the current, add aeration, and watch for 30 minutes

ExplanationCory catfish can breathe air through the gut and their slime-protected skin is relatively tolerant of drying. If the gill cover is moving there is a chance to save it: pick it up with wet hands, return it to the tank, hold its mouth into the current so water passes over the gills, add aeration, and do not give up for 30 minutes. Burial is premature; a motionless fish with gill movement is alive. Rubbing with cloth strips the remaining slime coat and opens more entry points for infection. A weakened fish will not eat, and food only fouls the water. After recovery, turn off the lights and keep it quiet, watch for fungus or red spots for several days, and if they appear isolate it and keep the water clean.

IssuesA lid gap and lack of weight allowed the jump-out. The owner did not know a dried fish with gill movement can still be saved, and no aeration was installed.

ImprovementWeight the lid and plug gaps. Run aeration at all times. Write the jump-out rescue procedure (wet hands, face the current, watch 30 minutes) on paper, post it, and share it with the family.

The redtail catfish (70 cm) in a 150 cm tank lies on its side on the bottom, and its gill cover moves only about 20 times a minute. It barely reacts to touch. Using a test strip for the first time just now, pH is low at 5.5 and nitrite is detected. Water is 27°C and the filter is running.

Which is the most appropriate first action?

1. Add pH adjuster to bring it back to 7.0 all at once
2. Take the fish out and force water into its mouth like artificial respiration
3. Do a 1/3 change with same-temperature dechlorinated water, set aeration to maximum, darken and observe, and if no improvement phone a vet right now
4. Leave it for 2–3 days without food until it recovers

AnswerC. Do a 1/3 change with same-temperature dechlorinated water, set aeration to maximum, darken and observe, and if no improvement phone a vet right now

ExplanationNormal gill movement is 60–120 times a minute; 20 is critical. The cause is water deterioration from low pH and nitrite buildup; do a 1/3 change with same-temperature dechlorinated water to dilute the toxins, set aeration to maximum, darken the tank to reduce stimulation, and observe for 30 minutes. If there is no improvement, phone a vet who sees large fish right now. Dumping in pH adjuster causes pH shock and instant death. Taking a large fish out is a heavy burden, and forcing water into its mouth is dangerous by any method other than facing it into the current underwater. Leaving it means the toxins remain and it dies. Continue 1/3 changes the next day and test pH and nitrite daily.

IssuesInadequate water changes for a large fish's waste output let pH fall sharply and nitrite build up. The owner used a test strip for the first time only after the fish rolled over, with no routine water testing.

ImprovementFor large catfish, do a 1/3 change twice a week and test and record pH and nitrite weekly. Learn the normal gill rate and test the water immediately if breathing speeds up or slows down. Find a vet who sees large fish in advance.

The pleco (25 cm) in a 90 cm tank cut its side on a sharp edge of driftwood, and a thin trail of blood spreads from the wound into the water. The pleco hides behind the driftwood and does not move. The cut is about 2 cm long and some of the bony plates around it have come off. Water is 26°C and water quality is normal.

Which is the most appropriate first action?

1. Take the fish out to press on the wound and stop the bleeding
2. Apply human styptic or antiseptic to the wound
3. Remove the sharp driftwood, keep it in an isolation container with clean water, darken it for rest, and act if cotton-like growth appears
4. The bleeding stops on its own, so do nothing and leave it in the community tank

AnswerC. Remove the sharp driftwood, keep it in an isolation container with clean water, darken it for rest, and act if cotton-like growth appears

ExplanationA fish's bleeding cannot be stopped by pressure underwater, and taking it out damages the slime coat and worsens the bleeding. Remove the sharp driftwood that caused it, keep the fish in an isolation container with clean water at 25–27°C, and darken it for rest; a small wound stops bleeding on its own. Human styptics and antiseptics are toxic to fish and foul the water. In the community tank other fish peck at the wound and the water is less stable. Watch the wound for several days; if cotton-like growth (fungus) appears keep the water clean, and if red spots spread consult a fish-knowledgeable shop or vet the same day. Round off driftwood edges and file sharp parts before adding it.

IssuesThe owner added driftwood with sharp edges unprocessed, without considering that a pleco rubbing against it could be cut. They did not know how fish bleeding is handled and had no isolation container ready.

ImprovementRound off edges on driftwood and rocks, and run your hand over them before adding to check for sharp points. Keep an isolation container, aeration, and dechlorinator on hand, and prioritize isolation and rest when bleeding occurs. Decide in advance never to use human medicine on fish wounds.

For a redtail catfish (60 cm) with abdominal swelling and hemorrhagic spots, a vet who sees fish has asked you to bring it in. It is a 40-minute drive. You have only thin plastic bags and a bucket. It is winter and 5°C outside. The fish lies motionless on the bottom with its spines raised.

Which is the most appropriate way to transport it?

1. Put water and the fish in a thin plastic bag and carry it on your lap
2. Put tank water in a bucket without a lid and set it on the back seat
3. Wrap it in a wet towel without water
4. Put it in a thick lidded container of tank water, insulate in a foam box, keep dark, and run a battery-powered air pump

AnswerD. Put it in a thick lidded container of tank water, insulate in a foam box, keep dark, and run a battery-powered air pump

ExplanationA large catfish's spines tear thin bags, and thrashing spills the water. Put the fish in a thick lidded container of tank water, insulate with a foam box or blanket, keep it dark, and supply oxygen with a battery-powered air pump. A thin bag tears, and on your lap the spines stab you. In an open bucket a thrashing fish jumps out, and in winter the water cools rapidly. A wet towel alone lets the gills dry and the fish suffocates within 40 minutes. Bring the tank size, temperature, pH, nitrite reading, last water-change date, diet, and photos of the symptoms, and phone the water data ahead. Avoid hard braking on the way and hand over the whole container on arrival.

IssuesThe owner had no thick container, foam box, or battery air pump for transporting a large fish, only thin bags in an emergency. They did not recognize the danger of the spines or the importance of winter insulation.

ImprovementKeep a thick lidded container sized for the fish, a foam box, a battery-powered air pump, and hand warmers on hand. Confirm by phone in advance whether the vet will see the fish and how to transport it, and make a habit of recording water data.

At 2 a.m. a noise wakes you, and all the cory catfish and the pleco in a 60 cm tank are lying down with rapid gill movement. The air pump has stopped and its tubing has come off. Water is 26°C and clear. You do not know whether the after-hours emergency animal hospital sees fish, and the phone does not connect.

Which is the most appropriate first action?

1. Restore the air pump to supply oxygen, do a 1/3 change with same-temperature dechlorinated water, and observe for 30 minutes
2. Bag everyone up and head to the after-hours emergency hospital
3. Take the fish out and move them to a bucket of tap water
4. Wait until morning and check the situation then

AnswerA. Restore the air pump to supply oxygen, do a 1/3 change with same-temperature dechlorinated water, and observe for 30 minutes

ExplanationThe cause is oxygen shortage from the stopped air pump, and restoring it to supply oxygen is the first step in saving them. Do a 1/3 change with same-temperature dechlorinated water to raise dissolved oxygen, turn off the lights, and observe for 30 minutes. Saving fish centers on improving water and oxygen; CPR is not possible. Few after-hours hospitals see fish, and transport stress makes things worse. Tap water is dangerous because of chlorine and temperature difference. Waiting until morning means they all die of oxygen shortage. If any fish does not recover, consult a fish-knowledgeable shop or vet the next morning. Secure air tubing with a check valve and clips so it cannot come off, and keep a spare air pump.

IssuesThe owner never anticipated the air tubing coming off and had not secured it. They did not understand that after-hours emergency care for fish barely exists and that home first aid is everything.

ImprovementFit air tubing with clips and a check valve, and keep a spare air pump plus a battery-powered pump. Check that aeration and filtration are running before bed. Remember that fish rescue means water and oxygen, and post the procedure on paper.

An owner living alone must be hospitalized for 2 weeks with a sudden illness. There is a redtail catfish (70 cm) in a 150 cm tank and plecos and cory catfish in a 90 cm tank. Family live far away, know nothing about fish, and can visit once a week. Admission is tomorrow.

Which is the most appropriate preparation?

1. Put 2 weeks' worth of food into the tanks at once
2. Ask the family to feed generously every day
3. Set an automatic feeder to dispense large amounts daily
4. Do a 1/3 water change today, ask the family only to feed a little and check temperature and equipment on their weekly visit, and give them a shop or acquaintance to contact

AnswerD. Do a 1/3 water change today, ask the family only to feed a little and check temperature and equipment on their weekly visit, and give them a shop or acquaintance to contact

ExplanationHealthy large catfish and plecos tolerate 1–2 weeks without food, but water deterioration from leftovers and waste becomes fatal within days. Before admission, do a 1/3 water change to put the water in good shape, and ask the family to feed a little on their weekly visit, check temperature and equipment, and give them a contact for emergencies. Dumping in food at once rots and wipes everyone out with ammonia poisoning. Generous daily feeding or heavy automatic feeding likewise ruins the water. For family without fish knowledge, keep their tasks minimal and hand them a written note of emergency signs (fish lying down, gasping at the surface) and the contact for a shop or a fish-knowledgeable acquaintance.

IssuesThere was no care plan for the owner's absence in case of sudden illness, and basic fish knowledge had not been shared with the family. The owner had not considered that the family might believe more food is better.

ImprovementMake an absence manual (feeding amount, normal temperature, equipment checks, emergency signs, contacts) and post it near the tank. Show family or friends the routine at least once. Test an automatic feeder on a low setting in advance.