Cichlids case method: 50 questions

A May evening. An office worker keeps 12 Lake Malawi mbuna in a 90 cm tank. On coming home, one yellow male is sitting still behind a rock, its belly distended, with a thin white thread-like string of feces hanging from the vent. When food is added it takes it into its mouth and spits it right back out. Breathing is rapid. Water 26°C, pH 8.2. The other fish are swimming normally.

Which is the most appropriate first action?

1. Feed frozen bloodworms to restore its appetite and build it up
2. Move it to a quarantine container right away, stop feeding, keep temperature and pH the same as the main tank, and seek advice the same day
3. Since the other fish are fine, wait and watch until next week's water change
4. Hold the fish in your hand and press its belly to release the gas

AnswerB. Move it to a quarantine container right away, stop feeding, keep temperature and pH the same as the main tank, and seek advice the same day

ExplanationA swollen belly, white stringy feces, spitting out food and rapid breathing are classic Malawi bloat (overgrowth of intestinal flagellates with enteritis), which often kills within days of onset. As soon as it is found, move the fish to a quarantine container, stop feeding, keep the same temperature and pH as the main tank to reduce the load on the gut, and consult a fish-savvy shop or an animal hospital the same day. Animal-based foods such as bloodworms do not suit the mbuna gut and are the biggest driver of worsening. Waiting means it is too late within days. Pressing the belly can rupture the gut or swim bladder. Caught early, there is room for recovery with medication, so do not waste time.

IssuesThe owner did not know that white stringy feces are an early sign of bloat and only noticed once the belly was clearly swollen. No quarantine container was kept on hand, so it had to be set up in a rush at night.

ImprovementCheck the color and shape of feces at every feeding and quarantine the moment white stringy feces appear. Keep a quarantine container with a spare heater and aeration permanently set up so it can be used at once with water from the main tank.

November. A 28 cm oscar (5 years old) is kept alone in a 120 cm tank. Over the past month, small whitish pits have been increasing on the head and around the eyes, and some areas along the lateral line look like holes. It is fed frozen beef heart every day. Water changes are once a month, and the test strip shows nitrate at the darkest color level. Appetite is still present.

Which is the most appropriate way to handle this fish?

1. Dab antiseptic on the holes with a cotton swab to prevent infection
2. Give more beef heart to build strength and wait for the holes to close on their own
3. Repeat 1/3 water changes every few days to lower nitrate, and switch the food to an oscar pellet diet
4. Raise the water temperature to 32°C to kill the protozoa

AnswerC. Repeat 1/3 water changes every few days to lower nitrate, and switch the food to an oscar pellet diet

ExplanationHoles and pits on the head and lateral line are hole-in-the-head disease, common in oscars, triggered by water deterioration from nitrate buildup and an unbalanced diet. The response is to repeat 1/3 water changes every few days to lower nitrate and switch to a formulated food containing vitamins and minerals. Giving more of an unbalanced food like beef heart will not help and the fat damages internal organs. Antiseptic damages the mucous membrane and makes things worse. High temperature causes oxygen shortage and metabolic strain in a large fish. If the holes spread, white stringy feces appear or the fish keeps losing weight, consult a fish-treating animal hospital within a few days to decide whether treatment for protozoa is needed.

IssuesMonthly water changes were not enough for the waste output of a large fish, so nitrate accumulated chronically. Feeding beef heart alone had thrown off the nutritional balance.

ImprovementFor large cichlids, make a weekly 1/3 water change the baseline and test nitrate with a strip once a week. Use a formulated pellet as the staple and keep live food or beef heart to occasional treats. Check the skin on the head daily and increase water-change frequency as soon as pits appear.

March, day 5 after adding four angelfish to a 60 cm tank. This morning two of them have white spots like grains of salt scattered over the body and fins and are rubbing themselves against the driftwood. One spot is also visible on a resident corydoras. Water is 24°C with the heater left at its lowest setting. The fish were put straight into the main tank with no quarantine.

Which is the most appropriate first action?

1. Raise the heater 1–2°C per day to around 28°C, do a 1/3 water change, and watch the whole tank
2. Remove the white spots one by one with tweezers
3. Raise the temperature to 30°C all at once to wipe out the parasites
4. Bag only the two spotted fish and return them to the shop

AnswerA. Raise the heater 1–2°C per day to around 28°C, do a 1/3 water change, and watch the whole tank

ExplanationWhite spots and flashing (rubbing) are ich (white spot disease), triggered by new fish and low water temperature. The ich parasite multiplies more slowly at higher temperatures, so raise 1–2°C per day to around 28°C and do a 1/3 water change to reduce parasites in the water. Since a resident fish is already affected, treat the whole tank as the target. The spots cannot be removed with tweezers and doing so only damages the skin. Heating all at once causes temperature shock and kills weakened fish. Returning only the sick fish leaves the parasites in the tank. If it keeps spreading over several days, use a fish medication as directed and consult a fish-savvy shop or hospital the same day.

IssuesNew fish were introduced directly without quarantine in a treatment tank, spreading the disease to resident fish. The heater was left at its lowest setting in early spring, so the water was cold and immunity was lowered.

ImprovementAlways observe new fish in a separate container for two weeks before adding them to the main tank. Keep angelfish at 26–28°C year-round. For the first week after introduction, check the body and fins daily and start treatment the moment even a single spot appears.

August. A 20 cm flowerhorn (3 years old) kept alone in a 90 cm tank. Because its eager eating is so endearing, it is fed generous amounts of sinking pellets three times a day. For three days it has passed no feces, its belly bulges out on both sides and it sits still on the bottom. Its response to food is dull, though it still takes some. No wounds or hemorrhagic spots on the body. Water 28°C, pH 7.2.

Which is the most appropriate first action?

1. Increase the amount of food to get the gut moving and pass feces
2. Fast for 2–3 days, keep the temperature steady, do a 1/3 water change, and check daily for feces
3. Massage the belly by hand to push the feces out
4. Crush a small amount of a human laxative and mix it into the food

AnswerB. Fast for 2–3 days, keep the temperature steady, do a 1/3 water change, and check daily for feces

ExplanationFeeding a greedy flowerhorn large amounts three times daily leads to indigestion and constipation; the belly swells and the fish stops moving. First fast it for 2–3 days to rest the gut, keep the temperature steady, do a 1/3 water change to tidy up water quality, and check daily whether feces are passed. More food only burdens the gut further. Massaging the belly damages internal organs. A human laxative has unknown effects and dosing in fish and is dangerous. If no feces pass after fasting, white stringy feces appear, scales stand out, or the fish floats or sinks, enteritis or internal disease is possible; consult a fish-treating animal hospital within a few days.

IssuesThe owner enjoyed the fish begging and made overfeeding three times a day a habit. Feces were not checked routinely, so the problem was only noticed after three days.

ImprovementFeed once or twice a day, only what is eaten within 2–3 minutes, and set one fasting day per week. Check daily for feces and their shape; if none for two days, switch to fasting. Record belly width viewed from directly above.

June. Lake Malawi cichlids are kept in a 90 cm tank. One female has the underside of her mouth puffed out and has been hiding behind rocks for nearly three weeks without eating anything. She seems to be getting thin, which is worrying. At times something seems to move inside her mouth. No white spots or wounds on the body, breathing is calm. pH 8.3, water 26°C.

Which is the most appropriate way to handle this fish?

1. Force the mouth open, remove the contents, and make her eat
2. Judge it to be disease and add fish medication to the main tank
3. Recognize mouthbrooding, keep observing quietly, and if you want to save the fry move the female to a breeding box or separate container
4. Since she will not eat, force food into her mouth by hand

AnswerC. Recognize mouthbrooding, keep observing quietly, and if you want to save the fry move the female to a breeding box or separate container

ExplanationFemale Lake Malawi cichlids brood fertilized eggs and fry in the mouth for 2–4 weeks, eating almost nothing during that time. The puffed mouth, hiding behavior and movement inside are normal signs of mouthbrooding and need no treatment. Keep observing in a calm environment where she is not chased, and if you want to keep the fry, gently move the female to a breeding box or separate container. Forcing the mouth open kills the eggs or fry and injures the jaw. This is not a disease, so fish medication is unnecessary, and dosing the main tank harms the filter bacteria and other fish. Force-feeding is just as dangerous. However, if she still does not eat after brooding ends, or white stringy feces or belly swelling appear, suspect disease and seek advice the same day.

IssuesThe owner did not know about mouthbrooding, a reproductive behavior specific to cichlids, and nearly mistook it for disease. No breeding box or separate container had been prepared to protect the female.

ImprovementResearch the breeding habits of the species in advance and understand that the brooding period and fasting are normal. Create several rock shelters where the female can hide, and be ready to move her to a breeding box if males harass her heavily.

A Sunday morning in September. Two oscars (25 cm) are kept in a 120 cm tank. The smaller one's belly is swollen, its scales stand out like a pinecone when viewed from above, and it has red hemorrhagic spots on its flanks and bulging eyes. Last week its tail fin was torn in a fight between the two. Uneaten food has built up on the bottom and no water change has been done for three weeks. The fish is motionless on the bottom.

Which is the most appropriate first action?

1. Draw off the abdominal fluid with a syringe to relieve it
2. Isolate it and start a 0.3–0.5% salt bath, clean the bottom of the main tank and change water, and consult a fish-treating hospital the same day
3. Wait for it to regain strength on high-calorie food
4. Press the scales down by hand to flatten them back

AnswerB. Isolate it and start a 0.3–0.5% salt bath, clean the bottom of the main tank and change water, and consult a fish-treating hospital the same day

ExplanationA swollen belly, pinecone scales, hemorrhagic spots and bulging eyes are classic Aeromonas infection; the fight wound and dirty water were the entry point. Once advanced it is hard to save, so isolate the sick fish and start a 0.3–0.5% salt bath in clean water, siphon the uneaten food from the main tank and do a 1/3 water change, and consult a fish-treating animal hospital the same day for a treatment decision. An amateur sticking a needle into the belly damages organs and spreads infection. This is not a disease that food cures, and leftover food fouls the water further. Pressing the scales will not restore them and only damages the skin. Transport in tank water and report the pH and temperature.

IssuesThe fish injured in the fight was not isolated and was left for three weeks in unchanged water with accumulated food, inviting bacterial infection. Keeping two oscars, a setup that invites fighting, with no isolation provisions.

ImprovementIsolate a large cichlid with a wound the day it is found. Fix a weekly 1/3 water change and bottom cleaning, and siphon out leftover food right after feeding. Keep multiple oscars separated with a divider or separate tanks, and always have a quarantine container ready.

April. Eight small Lake Tanganyika cichlids are kept in a 60 cm tank. Two were added from a shop a week ago. This morning one of the new fish keeps its left gill cover closed and moves only the right one rapidly, mouthing near the surface. The part visible through the gill opening is swollen and dark red. The other fish are also breathing somewhat fast. Water 26°C.

Which is the most appropriate first action?

1. Test ammonia and nitrite, do a 1/3 water change with water of the same temperature and pH, add aeration, and isolate the sick fish
2. Scrub inside the gill with a cotton swab to clean off the dirt
3. Since it is near the surface, feed it to calm it down
4. Only add aeration and wait for the new fish to recover on its own strength

AnswerA. Test ammonia and nitrite, do a 1/3 water change with water of the same temperature and pH, add aeration, and isolate the sick fish

ExplanationOne gill held shut with rapid breathing and a swollen dark-red gill is classic gill disease or gill parasites, arising when new fish and water deterioration coincide. First test ammonia and nitrite with a strip, do a 1/3 water change with water of the same temperature and pH, add aeration to secure oxygen, and move the sick fish to a quarantine container. Gills are delicate; scrubbing with a swab causes bleeding and leads straight to suffocation. A fish in respiratory distress will not eat and the food fouls the water. Left alone, parasites spread to the other fish. If there is no improvement after isolation, bleeding from the gills, or several fish worsen at once, consult a fish-savvy shop or hospital the same day and consider antiparasitic treatment.

IssuesNew fish were put into the main tank without quarantine, and the gill parasites they carried began spreading to resident fish. The early sign of fast breathing in the other fish was also missed.

ImprovementObserve new fish in a separate container for two weeks before adding to the main tank. Watch the movement of both gill covers daily and isolate at once any fish holding one side shut. Test ammonia and nitrite with a strip once a week.

July. Fifteen mbuna in a 90 cm tank. Since last week they have been fed generous amounts of frozen bloodworms daily. Today three are motionless behind rocks; two of them have swollen bellies and white stringy feces, and one spits out food. Yesterday one died suddenly. pH 8.0, water 27°C, ammonia and nitrite zero. The filter is working normally.

Which is the most appropriate response to this situation?

1. Water quality is normal, so keep feeding, remove the dead fish and watch
2. Add double the recommended dose of fish medication to the whole main tank to cure it fast
3. Stop bloodworms immediately and fast the whole tank, isolate the three symptomatic fish, watch the rest, and consult a fish-treating shop or hospital the same day
4. Lower the pH to 7.0 to settle the gut

AnswerC. Stop bloodworms immediately and fast the whole tank, isolate the three symptomatic fish, watch the rest, and consult a fish-treating shop or hospital the same day

ExplanationFeeding herbivorous mbuna animal-based bloodworms daily causes intestinal flagellates to multiply and Malawi bloat breaks out across the group. Its hallmark is that it occurs because of diet even when water quality is normal. Stop bloodworms immediately and fast the whole tank, isolate symptomatic fish, and because a death has occurred, consult a fish-savvy shop or animal hospital the same day to decide on treatment. Continued feeding spreads the outbreak. Double-dosing medication causes poisoning and filter collapse. pH 7.0 is unsuitable for Lake Malawi fish and a sudden pH change adds a further blow. Match the quarantine container to the main tank at around pH 8 and the same temperature to minimize stress.

IssuesThe owner lacked the species-specific knowledge that mbuna are herbivores vulnerable to animal-based food and fed bloodworms daily. The cause was not considered when the first fish died, delaying the response until a group outbreak.

ImprovementFeed Lake Malawi herbivores a spirulina-based formulated food as the staple and never give bloodworms or beef heart. On any sudden death, immediately review food and water quality and check the feces of all fish. Research and record the diet of each species before keeping it.

October. Ten mbuna in a 90 cm tank. Of two males of the same blue color, the smaller has been cornered near the surface in a corner of the tank since morning and its color has darkened. Its tail fin is half torn, and several scales on its flank have come off, exposing white flesh. The larger male flares its fins and charges whenever it approaches. There are only three rocks for shelter.

Which is the most appropriate first action?

1. It is natural rank-setting, so do not intervene and watch until it is settled
2. Isolate the losing male with a divider or in a separate container and give a 0.3–0.5% salt bath in clean water
3. Hit the larger male to punish it and stop the attacks
4. Trim the torn fin with scissors to even out its appearance

AnswerB. Isolate the losing male with a divider or in a separate container and give a 0.3–0.5% salt bath in clean water

ExplanationMales of the same color fight fiercely over territory; the loser is driven into a corner, darkens, and dies from bacterial infection of its wounds. The basic response is to isolate the losing male immediately with a divider or in a separate container and give a 0.3–0.5% salt bath in clean water to prevent secondary infection. Left alone, it will be chased relentlessly in a tank with no escape and die of exhaustion. Hitting a fish does not stop the fighting and causes other injuries. Cutting the fin only adds wounds and is pointless. If white cotton appears on the wounds, treat as fungus; if pinecone scales or hemorrhagic spots appear, consult a fish-treating hospital the same day. Rebuild the main tank with more rocks to block lines of sight.

IssuesBeyond the stocking error of putting in two same-colored males, there were only three shelters for ten fish and no escape. Noticing the darkening, a sign of a loser, came late.

ImprovementKeep mbuna as one male with several females and do not double up same-colored males. Build rockwork with more gaps than fish and walls that block sight lines. Check every morning for darkened color and hiding in corners, and protect with a divider the day it is found.

A February night. A 30 cm oscar in a 120 cm tank was startled right after the lights went off and crashed into the rockwork. On inspection, only the right eye is bulging out markedly, with congestion around it. The left eye is normal. Water quality is good after last week's change, ammonia zero. The fish can swim but nearly bumps into the wall on its right side.

Which is the most appropriate way to handle this fish?

1. Push the bulging eye back in with a finger
2. Since it is not both eyes, judge it is not disease and leave it
3. Isolate it, keep clean water and dim lighting, remove sharp rocks, and consult a fish-treating hospital the same day
4. Put in one drop of human eye drops

AnswerC. Isolate it, keep clean water and dim lighting, remove sharp rocks, and consult a fish-treating hospital the same day

ExplanationProtrusion of just one eye is usually traumatic, from a collision or fight; protrusion of both eyes suggests infection or internal disease. Even with trauma, infection around the eyeball can lead to blindness or death, so keep clean water in a quarantine container, dim the lights for rest, remove sharp rocks to prevent another collision, and consult a fish-treating animal hospital the same day. Pushing the eye back destroys the eyeball and optic nerve. Leaving it misses progressing infection. Human eye drops are meaningless underwater and the ingredients are unsuitable. Recovery takes several weeks; keep the water clean with daily changes and go back if the eye clouds or enlarges.

IssuesSharp rockwork was placed in a large fish's tank without anticipating the risk of a startled crash when the lights went off. The owner did not know that sudden darkness panics fish.

ImprovementChoose rocks and driftwood without sharp edges for large cichlid tanks and keep open swimming space in the center. Turn lights off in stages with the room light still on. Move slowly when approaching the tank of an easily startled fish.

1 a.m. Woken by a noise, the owner goes to the living room and finds the lid of the 90 cm tank shifted and the 22 cm flowerhorn lying on the floor. Its body is still damp but the fin edges are starting to dry, and the gill covers barely move. The tank's water level is close to the lid, and it is unknown how many minutes have passed since it fell.

Which is the most appropriate first action?

1. Return it gently with wet hands, support it where the current is gentle so water flows over the gills, and wait several hours even if it does not move
2. Wipe its body with a dry cloth before returning it to the tank
3. If the gills are not moving it cannot be saved, so dispose of it
4. Hold it right away against the strong filter outlet to wake it up

AnswerA. Return it gently with wet hands, support it where the current is gentle so water flows over the gills, and wait several hours even if it does not move

ExplanationA jumped fish has room to recover if the gills are moving even slightly. Dry hands strip the slime coat, so pick it up with wet hands, return it to the tank, and support it head-upstream where the current is gentle so water passes over the gills. Keep watching for several hours even if it does not move, and add a slime-coat protectant at the recommended dose for the dried fins. Wiping with a dry cloth strips the entire slime coat and the fish later dies of fungus. Many fish recover even with weak gill movement, so do not give up early. A strong current topples a weakened fish and exhausts it. After recovery, withhold food for a few days, check daily for white cotton or lost scales, and seek advice if it worsens.

IssuesThe jumping power of a large fish was not anticipated; a light lid was used shifted, and the water level was raised close to the lid. Responding promptly to the nighttime noise was lucky; a later discovery would have meant death.

ImprovementUse a heavy glass lid or one with clips for large cichlids and block gaps with plastic sheet. Keep the water level several cm below the lid. Keep a slime-coat protectant on hand and share the post-jump procedure with the family.

May. Five angelfish in a 60 cm tank. The branchy driftwood added yesterday has sharp tips, and this morning one fish's long ventral fin is torn in the middle and hanging down, with redness at the base. No other fish are attacking. Water 27°C, pH 6.8. The fish eats, but its fin snags every time it goes near the driftwood.

Which is the most appropriate way to handle this fish?

1. A torn fin regrows, so leave the driftwood as it is
2. Remove the driftwood and file down the sharp parts; isolate the fish and give a salt bath in clean water while the fin regrows
3. Glue the torn part back together
4. Raise the water temperature to 32°C to speed regrowth

AnswerB. Remove the driftwood and file down the sharp parts; isolate the fish and give a salt bath in clean water while the fin regrows

ExplanationAn angelfish's long fins easily snag and tear on sharp driftwood or rocks. Remove the offending driftwood and file down or discard the sharp tips; isolate the fish and give a 0.3–0.5% salt bath in clean water to prevent secondary infection while the fin regrows. Fins regrow in a few weeks, but if the cause remains it will tear again and infection leads to fin rot. Glue is toxic and destroys tissue. 32°C is too high for South American species and weakens them through oxygen shortage and metabolic strain. If the redness at the base spreads, the fin dissolves and shortens, or white cotton appears, consult a fish-savvy shop or hospital the same day.

IssuesThe sharpness of the new decor's tips was not checked before adding it. The risk of a long-finned angelfish snagging on decorations was not considered, and the day-after check was late.

ImprovementRun a finger over driftwood and rocks and file down sharp spots before adding them. Choose tall plants and rounded driftwood for angelfish. Check all fish's fins the day after introduction and remove anything they snag on at once.

December. A 27 cm oscar in a 120 cm tank was startled when a visitor tapped the glass and crashed into it. Since then its mouth stays half open and will not close, and the upper lip is split and peeled back white. It drops any food it takes in. Breathing is fast but both gills are moving. Water quality is good.

Which is the most appropriate way to handle this fish?

1. Close the mouth with your fingers and hold it back in position
2. Since it cannot eat, force food deep into its mouth
3. Isolate it for rest, offer small soft food while watching, and consult a fish-treating hospital within a few days
4. Dissolve a human painkiller in the water to ease the pain

AnswerC. Isolate it for rest, offer small soft food while watching, and consult a fish-treating hospital within a few days

ExplanationMouth injury from a collision can involve jaw dislocation or fracture. Isolate the fish away from stimulation, offer a small amount of small, soft food to see whether it can eat, and if the mouth stays open consult a fish-treating animal hospital within a few days. Pushing the jaw back with fingers further damages bone and joint. Force-feeding widens the mouth wound and causes aspiration. Human painkillers are harmful to fish and the dose is unknown. Bacteria entering the split lip can progress to mouth-rot-like symptoms, so keep the quarantine water clean with daily 1/3 changes. A large fish can tolerate a few days without eating, but always seek advice if it exceeds a week.

IssuesThe visitor was not stopped from tapping the glass, causing the startled fish to crash. It was not anticipated that a large fish's collision could cause serious mouth or eye injury.

ImprovementPost a "do not tap" sign on the tank and dim the lights or cover it with cloth when visitors come. Allow wide swimming space with a layout that is less likely to injure on impact. Check mouth movement and feeding daily and keep a container ready for isolation if anything is off.

January. Ten mbuna in a 90 cm tank. An uncovered heater was run through a gap in the rocks. This morning one fish has a white band of discoloration on its flank with scales peeled back and flesh showing. Last night that fish was seen sleeping wedged between a rock and the heater. Water is a normal 26°C. The fish can swim but keeps rubbing the discolored area.

Which is the most appropriate way to handle this fish?

1. Put a guard on the heater and move it away from the rocks; isolate the fish, keep clean water, and prevent infection with small daily water changes
2. It is a burn, so apply human burn ointment
3. Turn the heater off completely to lower the temperature
4. Remove and tidy the peeled scales with tweezers

AnswerA. Put a guard on the heater and move it away from the rocks; isolate the fish, keep clean water, and prevent infection with small daily water changes

ExplanationA fish in contact with an unguarded heater suffers a low-temperature burn: a white band of discoloration on the flank and peeling scales. First fit a guard on the heater and move it away from the rocks to prevent recurrence; isolate the fish and prevent infection with small daily water changes in clean water. Ointment washes off underwater and its oils foul the water. Turning the heater off weakens all the fish as winter water temperatures drop. Removing peeled scales enlarges the wound. If white cotton appears on the burn, give a salt bath for fungus; if it swells red or ulcerates, consult a fish-savvy shop or hospital the same day. Recovery takes several weeks.

IssuesNo heater guard was fitted, and the heater was run through a rock gap in a layout where a fish could get wedged against it. The habit of fish resting in narrow gaps at night was not considered.

ImprovementAlways use a guarded heater, placed away from the rockwork where there is water flow. Do not create gaps a fish can get wedged in. Check both flanks of every fish each morning and isolate at once on seeing white discoloration.

An April evening. The rockwork in a 90 cm tank collapsed after the fish dug in the sand. One fish is trapped under a rock with only its tail visible, moving slightly. Another rock is tilted and unstable and looks ready to collapse in a chain if touched. The other fish are huddled in a corner, startled. Reaching in requires lifting the rocks.

Which is the most appropriate first action?

1. Pull the fish out by its tail
2. Support the tilted rock with one hand while slowly lifting the rocks from the top down, free the fish, and isolate it
3. Wait for the fish to work its way out on its own
4. Shake the tank to shift the rocks

AnswerB. Support the tilted rock with one hand while slowly lifting the rocks from the top down, free the fish, and isolate it

ExplanationA trapped fish cannot breathe under the pressure and dies within minutes, so rescue it at once. However, putting a hand near unstable rocks risks a chain collapse that endangers both fish and hand, so support the tilted rock with one hand and slowly lift the rocks from the top down to free it. Pulling the tail strips scales and breaks bones. Waiting for it to escape means death by crushing. Shaking the tank drops other rocks that crush the fish and can crack the glass. After rescue, isolate it in clean water to rest; if it swims tilted or there is visible bruising on the flank, consult a fish-treating hospital the same day. To prevent recurrence, set rocks directly on the bottom glass and bond them in place.

IssuesThe owner did not know cichlids dig sand and topple rockwork, and had stacked rocks on top of the sand. The danger of a fish being pinned in a collapse and the risk of breaking the tank glass were not anticipated.

ImprovementSet rockwork directly on the bottom glass and fix it with aquarium adhesive or plastic sheet so it cannot collapse even when dug under. Do not lean large rocks against the tank walls. Check rock stability regularly when a fish is digging heavily.

July. In a 60 cm tank, a mbuna's mouthbrooding has finished and about 20 fry have begun swimming free. The canister filter intake has no sponge, and this morning three fry are stuck to it motionless, one of them still moving its fins. The flow at the intake is strong. Other fry are swimming close to being drawn in.

Which is the most appropriate first action?

1. Stop the filter, free the fry, fit a sponge on the intake, then restart
2. Wait for the fry to free themselves
3. Increase the intake flow to keep the other fry away
4. Pull the fry off hard with your fingers

AnswerA. Stop the filter, free the fry, fit a sponge on the intake, then restart

ExplanationFry are weak swimmers and get stuck to the filter intake and die from the pressure. First switch off the filter to remove the flow, then gently free and collect the fry. Fit a sponge on the intake before restarting to prevent recurrence. Waiting without stopping the flow leaves them stuck until they die, and increasing the flow draws in the other fry too. Pulling hard with fingers tears their tiny bodies. Move the collected fry to a breeding box or separate container and watch weak ones for a few hours. A brief filter stop does not affect filtration, but if it is off for tens of minutes or more, check that the water in the media has not gone foul before restarting.

IssuesThe owner did not anticipate fry emerging after mouthbrooding and had no sponge on the intake. It was not known that fry cannot swim against a canister filter's suction.

ImprovementAlways fit a sponge on the intake of a cichlid tank and prepare a breeding box or separate container before fry appear. Begin preparing for fry as soon as a mouthbrooding female is spotted, and check around the intake every morning.

A November morning. The lid of the 60 cm living-room tank was half open, with signs that the pet cat had dipped its forepaw in the water. One angelfish's dorsal fin is ripped, there are three parallel scratch marks on its flank, and it is sitting startled in a bottom corner. The cat is watching the tank intently.

Which is the most appropriate first action?

1. Scold the cat so it never goes near again
2. Give the injured fish a salt bath in clean water while observing, and fit a heavy lid with clips to physically keep the cat out
3. The wounds are small, so leave it and wait for natural healing
4. Move the fish to the bathroom where the cat cannot go and keep it there

AnswerB. Give the injured fish a salt bath in clean water while observing, and fit a heavy lid with clips to physically keep the cat out

ExplanationScratches from a cat's claws readily admit bacteria, so isolate the fish and give a 0.3–0.5% salt bath in clean water while checking daily for secondary infection. At the same time, fit a heavy glass lid with clips so the cat cannot open it. Scolding does not remove the hunting instinct; the cat will try again. Leaving it leads to infection, fin rot or fungus. A bathroom is hard to heat and light and worsens the fish's environment. If white cotton appears, the wound swells red, or the fin dissolves, consult a fish-savvy shop or hospital the same day. The cat also licks the paw that touched the tank water, so keep things clean on its side too.

IssuesIn a home with a cat, the lid was left half open and the risk of the tank becoming the cat's plaything was underestimated. The infection risk from bacteria on the cat's paw entering the fish's wounds was also not considered.

ImprovementIn a home with a cat, make a heavy glass lid with clips standard, and do not leave anything above the tank the cat can perch on. Enforce physical separation: put the tank in a cabinet, or in a room the cat cannot enter.

March. A 90 cm tank with 12 mbuna was placed on cheap furniture. At night a leg of the furniture buckled, the tank tilted, and water began seeping from a seam. The water level is slowly dropping and the floor is wet. The fish can still swim. The full tank weighs about 180 kg and cannot be moved by one person. There is no spare tank, but there is a large plastic container and a storage box.

Which is the most appropriate first action?

1. Try to lift the tank as it is and lower it to the floor
2. The leak is small, so watch until morning
3. Unplug the heater and filter, transfer the tank water to the plastic container, evacuate the fish and filter media into it, and deal with the tank once it is lighter
4. Fill the plastic container with fresh tap water and move only the fish

AnswerC. Unplug the heater and filter, transfer the tank water to the plastic container, evacuate the fish and filter media into it, and deal with the tank once it is lighter

ExplanationA tilted full tank risks collapse and electric shock, so first cut the power to prevent the heater running dry as the level drops and any electrical leakage. Next transfer the tank water to the plastic container and evacuate the filter media and fish into it. Using the tank water avoids sudden pH and temperature changes, and including the media preserves the bacteria. Lifting a 180 kg tank injures your back and shattering glass makes it a major accident. Waiting until morning risks collapse, total loss and flood damage. Fresh tap water shocks mbuna with chlorine and temperature and pH differences. Add aeration to the evacuation container and set up again the next day or later on a stand rated for the load.

IssuesThe owner put a 90 cm tank on furniture not rated for the load without considering its full weight. No emergency container or aeration was prepared, so the nighttime response was delayed.

ImprovementSet the tank on a dedicated stand rated for its full weight and check the floor's strength as well. Keep a large lidded container for evacuating fish plus a spare air pump and heater on hand. Inspect the stand for warping and the glass seams monthly.

August. A 120 cm tank with one 25 cm oscar. The canister filter's plug was pulled out while vacuuming and not noticed until the following night. The water is cloudy white and smells slightly. The oscar is mouthing near the surface and its color has darkened. A test strip shows ammonia. The heater is working, water 28°C.

Which is the most appropriate first action?

1. Restart the filter as it is and wait for the cloudiness to clear
2. Replace all the water with fresh water to reset
3. Discard the water inside the filter, rinse the media lightly, then restart; do a 1/3 to 1/2 water change with same-temperature water, add aeration, and stop feeding
4. Feed to build strength and change the water tomorrow

AnswerC. Discard the water inside the filter, rinse the media lightly, then restart; do a 1/3 to 1/2 water change with same-temperature water, add aeration, and stop feeding

ExplanationInside a canister filter stopped for a full day the oxygen is gone and foul, decomposed water has collected. Restarting as is dumps that rotten water into the tank and weakens the fish at once, so discard the water inside, rinse the media lightly in tank water, then restart. At the same time, do a 1/3 to 1/2 water change with same-temperature water, add aeration to address ammonia and oxygen shortage, and stop feeding to avoid adding waste. A full water change loses the bacteria and causes long-term water collapse. Food fouls the water and worsens respiratory distress. Even one large fish produces a lot of waste, so test ammonia and nitrite again tomorrow and keep changing water. If gasping continues or the fish lies on its side, seek advice the same day.

IssuesThe possibility of the plug coming out during cleaning was not anticipated, and the stopped filter went unnoticed until the next day. There was no daily habit of checking that the equipment was running.

ImprovementGroup the tank's power connections where they cannot be pulled out and always check equipment after cleaning. Make a morning routine of checking the filter outflow and heater lamp. Keep a spare air pump and test strips so measurements can be taken at once when something is wrong.

A June afternoon. Four angelfish in a 60 cm tank. Half the water was changed in a hurry, and 10 minutes later the owner realized the dechlorinator had been forgotten. The fish are gasping hard at the surface, their gills are red and congested, and one is darting around frantically. The temperature was matched. Liquid dechlorinator is on hand.

Which is the most appropriate first action?

1. Immediately add the recommended dose of dechlorinator directly to the tank, mix it in, add aeration, and observe
2. Do another 50% change with tap water to dilute it
3. Net the fish and move them to a bucket of tap water
4. It is already too late, so do nothing and watch

AnswerA. Immediately add the recommended dose of dechlorinator directly to the tank, mix it in, add aeration, and observe

ExplanationChlorine in tap water destroys the gill membranes, causing respiratory distress and frantic swimming. Adding the recommended dose of dechlorinator directly to the tank and mixing it neutralizes the chlorine immediately, so add it without hesitation, add aeration, and observe. Another change with tap water adds more chlorine and worsens it. Moving fish to a bucket of tap water is the same. After 10 minutes recovery is very likely; this is no time to give up. For fish whose gills remain congested after neutralizing, feed lightly for a few days and keep the water clean; if breathing does not settle or a fish lies on its side, consult a fish-savvy shop or hospital the same day.

IssuesThe water change was rushed and the dechlorinator step was skipped. The procedure was not fixed, so water was poured in without checking. The harm chlorine does to gills was also underestimated.

ImprovementWrite the water-change sequence (fill bucket, add dechlorinator, match temperature, pour) on paper and post it beside the tank. Keep dechlorinator next to the tank and point-and-check that it went into the bucket before pouring.

A September night. A mosquito was spotted in the living room and insect spray was sprayed for a few seconds. The 90 cm tank's lid was half open and an air pump is pushing room air into the water. Thirty minutes later several mbuna are thrashing at the surface, swimming with violent body twisting, and one has gone over on its side. Temperature and pH are normal.

Which is the most appropriate first action?

1. Since they are thrashing, turn off the lights and leave them until morning
2. Spray again to kill every mosquito in the room first, then deal with it
3. Open the windows to ventilate, do a 1/3 to 1/2 water change with same-temperature, same-pH water, put activated carbon in the filter, and move the air pump intake to a clean location
4. Net the fish and rinse them in a basin of tap water

AnswerC. Open the windows to ventilate, do a 1/3 to 1/2 water change with same-temperature, same-pH water, put activated carbon in the filter, and move the air pump intake to a clean location

ExplanationInsecticide ingredients are highly toxic to fish and dissolve into the water through the lid gap and the air pump intake. First ventilate to lower the concentration in the air, do a 1/3 to 1/2 water change with same-temperature, same-pH water to dilute the chemical, and put activated carbon in the filter to absorb it. Move the air pump intake to another room or a clean location. Left alone, the chemical keeps dissolving in and wipes out the tank. Spraying again is out of the question. Rinsing fish in tap water is fatal from chlorine and slime-coat damage. Continue water changes and carbon replacement the next day, and isolate any fish on its side in a dark, quiet place. If it does not recover, consult a fish-savvy shop or hospital the same day.

IssuesInsect spray was used in the room with the tank without understanding that the air pump pushes room air into the water. Entry of fumes through the lid gap was also not anticipated.

ImprovementDo not use insecticide, air freshener, deodorizing spray or paint in the room with the tank. If unavoidable, seal the tank and stop the air pump, and ventilate thoroughly before restarting. Keep activated carbon on hand for emergencies.

February. Ten mbuna in a 90 cm tank. The pH had dropped to 7.2, so four times the recommended dose of a pH-raising product was added all at once. Fifteen minutes later several fish are drifting on their sides, moving their gills rapidly. A measurement shows pH has shot up to 8.8. Water 26°C, ammonia zero. Stock water at the same temperature as the tank can be prepared.

Which is the most appropriate first action?

1. Now add a pH-lowering product to neutralize it
2. Mbuna like high pH, so there is no problem; wait for recovery
3. Do a 1/3 water change with pH 7.2 water to bring the pH back toward where it was, increase aeration, and afterwards adjust gradually by 0.2–0.3 per day
4. Do a full water change to reset completely

AnswerC. Do a 1/3 water change with pH 7.2 water to bring the pH back toward where it was, increase aeration, and afterwards adjust gradually by 0.2–0.3 per day

ExplanationMbuna prefer high pH, but a jump from 7.2 to 8.8 in under an hour is pH shock, and lying on the side with rapid breathing are its symptoms. The problem is not the number but the speed of change. Do a 1/3 water change with pH 7.2 water, close to the original, to reverse the change, increase aeration, and wait for recovery. Then raise it gradually by 0.2–0.3 per day. Adding a pH-lowering product on top causes a sudden drop and a second shock. Just waiting lets damage to the slime coat and gills progress. A full water change loses the bacteria and creates another problem. If fish stay on their sides for over an hour or bleed from the gills, consult a fish-savvy shop or hospital the same day.

IssuesIn a rush to hit the pH number, four times the recommended dose was added at once, changing it faster than the fish could tolerate. The underlying cause of the pH drop (insufficient water changes, exhausted coral sand) had not been investigated.

ImprovementLimit pH adjustment to 0.2–0.3 per day and follow the recommended dose. Stabilize a mbuna tank's pH naturally with coral sand or oyster shell, measure weekly, and change water as soon as it starts to drop. Keep stock water at the same pH as the tank for emergencies.

3 p.m. in August. In a room with no air conditioning, a 30 cm oscar in a 120 cm tank keeps mouthing at the surface. The thermometer reads 33°C. The filter is running but there is no aeration, and the surface is covered with an oily film. There is no cooling fan, but there are frozen plastic bottles and an electric fan.

Which is the most appropriate first action?

1. Put several frozen bottles directly into the water to cool it fast
2. Add aeration to agitate the surface and break up the film, aim the electric fan at the surface, open the lid slightly, and lower the temperature 1–2°C at a time
3. Make ice water and do a 50% water change
4. Feed to build strength and wait for the night-time drop in temperature

AnswerB. Add aeration to agitate the surface and break up the film, aim the electric fan at the surface, open the lid slightly, and lower the temperature 1–2°C at a time

ExplanationIn hot water dissolved oxygen drops, and a surface film blocks oxygen uptake, so a large fish is the first to suffer oxygen shortage. First add aeration to agitate the surface, disperse the film and take in oxygen, then aim the fan at the surface to lower the temperature 1–2°C at a time by evaporative cooling. Open the lid slightly to let heat escape. Several frozen bottles placed directly in the water cause localized rapid cooling and temperature shock, so if used, use one slowly or cool from outside the tank. An ice-water change is fatal from the sudden change. Food increases oxygen consumption and fouls the water. Waiting until night means death from oxygen shortage. If the fish lies on its side and responds poorly, seek advice the same day.

IssuesA large fish's tank was placed in a room without air conditioning with no preparation for summer heat. There was no aeration, and the oily film, a sign of oxygen shortage, was not noticed.

ImprovementInstall a cooling fan or chiller before summer and run aeration year-round. Post a rule on the thermometer to act above 30°C. When away during the day, run the air conditioner or prepare shading and a fan to limit the rise.

A January morning. All five angelfish in a 60 cm tank are sunk to the bottom with fins clamped and darkened color. The thermometer reads 18°C and the heater lamp is off. It was 26°C the night before. They do not respond to food. There is one spare heater. The room heating can be turned on.

Which is the most appropriate first action?

1. Put in the spare heater and bring it back to 26°C at about 1°C every 1–2 hours, withholding food until the temperature is back
2. Pour in hot water directly to get back to 26°C within minutes
3. Set the spare heater to maximum and take it straight up to 30°C to activate immunity
4. The water is cold, so feed more to warm their bodies

AnswerA. Put in the spare heater and bring it back to 26°C at about 1°C every 1–2 hours, withholding food until the temperature is back

ExplanationAn 8°C drop from heater failure is dangerous, but bringing it back all at once causes temperature shock. Put in the spare heater, return to the original 26°C at about 1°C every 1–2 hours, and assist with room heating. Withhold food until the temperature is back. Pouring in hot water causes localized overheating with burns and sudden change. 30°C is too high for South American angelfish and is also a sudden change. In cold water digestion stops and food rots in the gut. After recovery, watch for ich for a few days. If the low temperature lasted a long time, or a fish still lies on its side after warming, consult a fish-savvy shop or hospital the same day.

IssuesHeater lifespan and failure were not anticipated, and the temperature drop went unnoticed until morning. There was no temperature alarm or other way to know about an overnight problem.

ImprovementReplace heaters every 1–2 years and keep a spare. If possible, use two low-wattage heaters for redundancy. Check the thermometer every morning and install an alarm thermometer. Decide in advance how to keep warm during a winter power outage or failure.

10 p.m. in October. A 28 cm oscar in a 120 cm tank is lying on the bottom; the gill covers move slowly but it barely responds to touch. No wounds or white spots on the body. Nothing was done today, but a week ago during a big cleaning all the filter media were washed in tap water. Test strips show high ammonia and nitrite. Water 27°C.

Which is the most appropriate first action?

1. Support the fish by hand and keep it swimming
2. Do a 1/3 to 1/2 water change with same-temperature, same-pH water, turn aeration to maximum, turn off the lights, stop feeding, and contact a fish-treating hospital, bringing the fish in its tank water
3. Add fish medication right away and watch
4. Take the fish out and put it in a bucket of fresh tap water

AnswerB. Do a 1/3 to 1/2 water change with same-temperature, same-pH water, turn aeration to maximum, turn off the lights, stop feeding, and contact a fish-treating hospital, bringing the fish in its tank water

ExplanationWashing all the media in tap water killed the bacteria, and ammonia and nitrite built up to toxic levels. Life support for the fish is improving the water itself: do a 1/3 to 1/2 water change with same-temperature, same-pH water to dilute the toxins, turn aeration to maximum to secure oxygen, turn off the lights and stop feeding for rest. If there is no improvement, contact a fish-treating hospital and bring the fish in its tank water. Forcing a prostrate fish to swim exhausts it. Medication is pointless since the cause is water quality and burdens a weakened fish. Tap water adds a further blow from chlorine and pH difference. Keep measuring and changing water daily from the next day; if the gills are dark red or gasping continues, seek advice again.

IssuesThe owner made the worst mistake of washing all media in tap water, destroying the filter bacteria. For the week after, water quality was not tested with strips, and the problem went unnoticed until the fish was lying down.

ImprovementOnly rinse media lightly in tank water and never replace all of it at once. After a big cleaning, test ammonia and nitrite daily for a week and change water if they rise. Keep test strips and a spare air pump on hand, and write down the emergency water-change procedure.

September. Six angelfish in a 60 cm tank. The largest female has visibly wasted away over two weeks; the flesh along her back has gone and she is knife-thin. There are two white pits above the eyes on her head, and she trails white, semi-transparent feces. She comes to the food but lets go of it as soon as it is in her mouth. Water changes are every two weeks and nitrate reads at the high end of the color scale.

Which is the most appropriate way to handle this fish?

1. She is thin, so increase high-fat food to fatten her up
2. Scrub the pits with a cotton swab to clean them
3. The other fish are fine, so treat it as old age and watch
4. Isolate her, increase water changes to lower nitrate, photograph the white feces and head pits, and consult a fish-treating hospital within a few days

AnswerD. Isolate her, increase water changes to lower nitrate, photograph the white feces and head pits, and consult a fish-treating hospital within a few days

ExplanationHead pits, white semi-transparent feces and rapid wasting are hole-in-the-head disease, common in angelfish and discus, involving intestinal flagellates together with nitrate buildup and malnutrition. Isolate the sick fish in clean water and increase the main tank's water-change frequency to lower nitrate. The feces and pits are diagnostic clues, so photograph them and consult a fish-treating animal hospital within a few days to consider antiparasitic treatment. High-fat food cannot be absorbed and damages the gut further. Scrubbing the pits causes secondary infection. Progressive wasting kills within weeks, so do not dismiss it as old age. Offer small amounts of formulated food and do not force it if she will not eat.

IssuesWater changes every two weeks let nitrate accumulate and lowered immunity. The color of the feces was not checked when she began to lose weight, and the cause was not considered until the back muscle was gone.

ImprovementMake a weekly 1/3 water change the baseline for an angelfish tank and test nitrate twice a month. Get in the habit of checking feces color at feeding (brown is normal; white or clear is abnormal), and move to isolation and consultation as soon as wasting or head pits are seen.

April. Twelve mbuna in a 90 cm tank. A week ago three were added from a shop, bag water and all, straight into the main tank. This morning more than 10 of the 15 fish have white spots spreading over body and fins, and many are rubbing against the rocks. Several have clamped fins and rapid breathing. Water 25°C, pH 8.2. The owner has no treatment container.

Which is the most appropriate response to this situation?

1. Bag only the spotted fish and return them to the shop
2. Ich clears up on its own, so feed more and watch
3. Raise the main tank 1–2°C per day to around 28°C, do 1/3 water changes every few days, and if the spread does not stop use a fish medication as directed and consult a shop or hospital
4. Take all the fish out at once, disinfect the tank with boiling water, then put them back

AnswerC. Raise the main tank 1–2°C per day to around 28°C, do 1/3 water changes every few days, and if the spread does not stop use a fish medication as directed and consult a shop or hospital

ExplanationAdding the bag water introduced the ich parasite, which spread through the whole tank in a week. When most of the fish are affected, treat the main tank itself: raise 1–2°C per day to around 28°C and repeat 1/3 water changes every few days to reduce parasites in the water. If it still spreads, use a fish medication as directed and consult a fish-savvy shop or hospital the same day. Returning only the sick fish leaves parasites in the water. Ich does not clear on its own; left alone it spreads to the gills and suffocates the fish. Removing all fish and sterilizing with boiling water wipes out the bacteria, and the fish weaken in their holding container. Oxygen drops while heating, so add aeration.

IssuesNew fish were added to the main tank without quarantine, bag water included, bringing pathogens straight in. With no treatment container, there was no way to isolate individually.

ImprovementAlways observe new fish in a separate container for two weeks and never add bag water to the main tank. Keep a quarantine/treatment container with a heater and air pump on hand. For the first week after introduction, check every fish's body each morning and act as soon as a spot appears.

June. Eighteen mbuna in a 90 cm tank. Since three days ago one or two have died each day, four lost so far. The dead fish had swollen bellies, and several of the survivors are passing white stringy feces and spitting out food. Water is pH 8.1, ammonia and nitrite zero. Recently they were fed frozen bloodworms and dried daphnia daily. With so many fish, shelter is in short supply.

Which is the most appropriate response to this situation?

1. Water quality is normal, so treat the cause as unknown and watch
2. Add three times the recommended dose of fish medication to the main tank to cure all the fish at once
3. Remove the dead fish, switch to a spirulina-based food, and feed as usual
4. Stop animal-based food immediately and fast the whole tank, isolate symptomatic fish, and because deaths continue, consult a fish-treating shop or hospital the same day

AnswerD. Stop animal-based food immediately and fast the whole tank, isolate symptomatic fish, and because deaths continue, consult a fish-treating shop or hospital the same day

ExplanationFeeding herbivorous mbuna animal-based food daily makes intestinal flagellates multiply and Malawi bloat breaks out across the group. Stress from overcrowding and lack of shelter accelerates it. Its hallmark is that it occurs from diet and environment even when water quality is normal. Stop animal-based food immediately and fast the whole tank, and isolate symptomatic fish. At the stage of daily deaths, medication is often needed, so consult a fish-savvy shop or animal hospital the same day. Watching leads to total loss. Overdosing medication causes poisoning and filter collapse. Changing the food but continuing to feed without fasting lets the enteritis progress. Match the quarantine container to the main tank at around pH 8 and the same temperature.

IssuesThe owner did not know mbuna are herbivores and used animal-based food as the staple. Overcrowding at 18 fish with too little shelter made stress chronic, and the cause was not investigated when the first fish died.

ImprovementFeed Lake Malawi herbivores only a spirulina-based formulated food. At the first death, check food, water quality and feces all at once. Relieve overcrowding and build rockwork with more hiding places than fish. Keep a quarantine container on hand and isolate the day white feces are seen.

November. A 25 cm flowerhorn (4 years old) kept alone in a 90 cm tank. There is a red, raw ulcer on the side of its forehead hump with a white rim. It is where it scraped itself hitting the lid a week ago. Appetite has dropped and it spends more time still on the bottom. Uneaten food has built up in the substrate and the last water change was three weeks ago.

Which is the most appropriate way to handle this fish?

1. Siphon out the leftover food and do a 1/3 water change, observe while giving a 0.3–0.5% salt bath in clean water, and consult a fish-treating hospital the same day if the ulcer spreads
2. Apply human antibiotic ointment to the ulcer
3. The hump is fat, so leaving it is no problem
4. Raise the water temperature to 32°C to speed healing

AnswerA. Siphon out the leftover food and do a 1/3 water change, observe while giving a 0.3–0.5% salt bath in clean water, and consult a fish-treating hospital the same day if the ulcer spreads

ExplanationThis is the classic course of a scrape becoming bacterially infected in dirty water and turning into a red ulcer. Siphon out the leftover food and do a 1/3 water change to clean the water, and observe daily while a 0.3–0.5% salt bath suppresses secondary infection. If the ulcer spreads, scales stand out, or hemorrhagic spots or bulging eyes appear, suspect progressing Aeromonas infection and consult a fish-treating animal hospital the same day. Ointment washes off underwater, does nothing, and fouls the water. A wound on the hump is an infection entry point that cannot be ignored. Heating to 32°C is counterproductive through metabolic strain and oxygen shortage. Since it is kept alone, treating in the main tank is acceptable, but a quarantine container that allows daily water changes makes water management easier.

IssuesThe scrape from the collision was left for a week, and bacterial infection set in from water full of leftover food. Going three weeks without a water change is a fatal lapse for a large fish.

ImprovementStart water changes and a salt bath the day a wound is found. Even for a single large fish, fix a weekly 1/3 water change and siphoning of leftover food. Leave room between the lid and the surface to reduce collisions when startled.

March. Fourteen mbuna in a 90 cm tank. The largest male has claimed half the tank as his territory and chases the other fish. This morning three fish have lost scales and have shallow wounds on their flanks, and two are darkened in a corner. There are few rocks and no refuge outside the dominant male's territory. There is only one container for isolating the losers one at a time.

Which is the most appropriate response to this situation?

1. Isolate only the three injured fish in turn and leave the main tank as it is
2. Get rid of the dominant male to make a peaceful tank
3. Things settle once the hierarchy is set, so do not intervene
4. Temporarily isolate the dominant male, add rocks and rebuild the layout to block sight lines before returning him, and observe the injured fish in clean water

AnswerD. Temporarily isolate the dominant male, add rocks and rebuild the layout to block sight lines before returning him, and observe the injured fish in clean water

ExplanationWhen several fish are injured at once, the cause lies in the dominant male and the territorial structure. Temporarily isolate the dominant male, and while he is out add rocks to create walls and gaps that block sight lines, resetting the territories before returning him. In the new layout his dominance fades and aggression softens. Observe the injured fish in clean water and give deep wounds a salt bath. Isolating only the losers just creates the next target. Disposal is unnecessary; this is an environmental design problem. Leaving it leads to infected wounds and death from exhaustion. If white cotton appears on wounds or pinecone scales develop, consult a fish-savvy shop or hospital the same day. Aim for more hiding places than fish.

IssuesThere were few rocks for 14 fish, with no territorial boundaries or refuges. The owner did not understand that mbuna divide a tank into territories and left overcrowding and lack of shelter unaddressed.

ImprovementStack rocks across the whole mbuna tank to create a structure with no clear sight lines. Introduce new fish or change the layout for several fish at once to reset territories. Check flank scales and fish in corners every morning, and rethink the structure on seeing darkened color.

July. Lake Malawi cichlids in a 90 cm tank. A female holding eggs in her mouth has been relentlessly chased by another male, and this morning she has spat out some of the eggs and the edge of her mouth is split and red. She is weakened, hiding behind rocks and breathing fast. She has not eaten for nearly two weeks since she began brooding. A breeding box and quarantine container are ready.

Which is the most appropriate first action?

1. Take all the remaining eggs out of her mouth and make her eat
2. Hit the chasing male to punish him and leave the female where she is
3. Put the spat-out eggs back into her mouth
4. Gently move the female to a quarantine container with the same water as the main tank, keep it dark and quiet, watch the mouth wound, and try a small amount of food she can manage

AnswerD. Gently move the female to a quarantine container with the same water as the main tank, keep it dark and quiet, watch the mouth wound, and try a small amount of food she can manage

ExplanationA female fasting while mouthbrooding is already low on strength, and if she is chased and her mouth injured she can weaken and die. Gently move her to a quarantine container with the same pH and temperature as the main tank, keep it dark and quiet, and watch the mouth wound. Leave it to her whether to keep brooding or release the fry; if she releases them, try a small amount of small, soft food. Forcing out the remaining eggs injures the jaw and kills the eggs. Hitting the male does not stop the chasing and causes other injuries. Returning spat-out eggs is impossible and widens the mouth wound. If the wound turns white and soggy, she still cannot eat, or pinecone scales appear, consult a fish-treating hospital within a few days.

IssuesThe mouthbrooding female was not moved to a place where she would not be chased, and was exposed to fighting in a weakened state. A breeding box was ready but was not used when brooding was confirmed.

ImprovementOnce mouthbrooding is confirmed, move the female early to a breeding box or separate container. Add rock shelters to the main tank so females can escape male aggression. Check a brooding female's condition and breathing daily and isolate at once if she is too thin or being chased.

May. To change the layout of a 60 cm tank, the mbuna were netted out one by one with a coarse-mesh net into a bucket. The day after returning them, two have lost scales on their flanks and the skin looks faintly clouded white as if the slime coat has come off. One had its fin spines tangled in the net and was freed by force. Temperature and pH are normal.

Which is the most appropriate way to handle these fish?

1. Add a slime-coat protectant at the recommended dose, keep clean water, isolate the injured fish, and check daily for white cotton or redness
2. The white cloudiness is dirt, so rub it off with a finger
3. Scales regrow, so nothing needs to be done
4. Add fish medication to the main tank as a disinfectant

AnswerA. Add a slime-coat protectant at the recommended dose, keep clean water, isolate the injured fish, and check daily for white cotton or redness

ExplanationA coarse net tangles in a cichlid's fin spines and scales, causing scale loss and slime-coat damage. The slime coat is the body's first barrier against pathogens; once stripped it becomes the entry point for fungus and bacterial infection. Add a slime-coat protectant at the recommended dose, keep clean water, isolate the injured fish, and check daily for white cotton or redness. The white cloudiness is already-stripped slime coat; rubbing damages it further. Scales do regrow, but without care to prevent infection the fish worsens within days. Preventive medication burdens uninjured fish and the bacteria. If white cotton appears, give a salt bath for fungus; if there is red swelling, seek advice the same day.

IssuesA coarse net was used on cichlids with hard fin spines, and tangled spines were freed by force. The owner did not know the risk of slime-coat damage when moving fish.

ImprovementMove fish by scooping them in water with a container or bowl, or use a soft fine-mesh net. If spines tangle, submerge the net and wait for them to free themselves. After moving, add a slime-coat protectant at the recommended dose and watch the skin closely for three days.

October. Three angelfish share a 60 cm tank with five tiger barbs added last week. This morning the tips of all the angelfish's long dorsal and ventral fins are ragged, and one is nipped down to the base with red congestion. The barbs have been seen repeatedly following the angelfish and pecking at their fins.

Which is the most appropriate response to this situation?

1. The angelfish will fight back eventually, so leave it
2. Feed the barbs more so they have no need to nip fins
3. Move the barbs to another tank to end the mix, and give the angelfish a salt bath in clean water while the fins regrow
4. Trim the ragged fins straight with scissors

AnswerC. Move the barbs to another tank to end the mix, and give the angelfish a salt bath in clean water while the fins regrow

ExplanationFin-nipping species such as tiger barbs are natural enemies of slow-moving, long-finned angelfish. Unless the aggressors are moved to another tank and the mix ended, the injuries will keep increasing. Give the angelfish a 0.3–0.5% salt bath in clean water and wait for the fins to regrow. Nipping is a habit, not hunger, so more food will not stop it. Left alone, bacterial infection at the fin base leads to fin rot. Cutting with scissors only adds wounds. If redness at the base spreads or fins dissolve and cloud white, consult a fish-savvy shop or hospital the same day. Research compatibility before choosing tankmates.

IssuesThe tankmates' habits were not researched, and fin-nippers were housed with angelfish. The pecking was observed, yet nothing was done until fins were nipped to the base.

ImprovementBefore adding new fish, check compatibility with the species kept and avoid fin-nippers and fast swimmers. Check fin edges daily after introduction and separate at the first sign of pecking. Keep a spare tank or quarantine container ready.

An August afternoon. A 5-year-old put about half a bag of oscar pellets into the 90 cm tank. Pellets cover the entire bottom and the water is already turning cloudy white. The oscar (25 cm) ate for a while but is now mouthing near the surface. It was discovered two hours after the pellets went in. Water 29°C.

Which is the most appropriate first action?

1. The oscar is eating, so wait until it finishes everything
2. Remove all the sunken pellets with a net or siphon, do a 1/3 to 1/2 water change with same-temperature water, and add aeration
3. Do a full water change to reset completely
4. Turn up the filter and wait for the cloudiness to clear

AnswerB. Remove all the sunken pellets with a net or siphon, do a 1/3 to 1/2 water change with same-temperature water, and add aeration

ExplanationA large amount of leftover food rots within hours, producing ammonia, and the decay bacteria consume oxygen and cause oxygen shortage. Gasping is the early sign. First physically remove all the sunken pellets with a net or siphon, do a 1/3 to 1/2 water change with same-temperature water, and add aeration. Even a large fish cannot eat that much, and overeating causes indigestion and enteritis. A full water change loses the bacteria so ammonia cannot be processed from the next day. The filter alone cannot keep up with the speed of decay. Test ammonia and nitrite again tomorrow and keep changing water, and stop feeding for 2–3 days. If the fish lies on its side or the gills are dark red, seek advice the same day.

IssuesFood was kept within a child's reach with nothing to prevent it going into the tank. Discovery took two hours, during which decay progressed and caused oxygen shortage and rising ammonia.

ImprovementStore food out of children's reach and hand over single portions in a small container. Teach children by feeding together. Explain to the whole family how to report changes in the tank (cloudiness, smell, gasping).

9 p.m. in January. A diagonal crack has been found in the lower corner of the front glass of a 120 cm tank, with water slowly seeping out. Two oscars (25 cm) are swimming in it. The crack seems to be lengthening over time. There is no spare tank, but there are two large storage boxes, a spare air pump and one heater.

Which is the most appropriate first action?

1. Tape over the crack and wait until morning
2. Unplug the heater and filter, transfer the tank water and media into the storage boxes, house the oscars one per box with the heater and air pump, and empty the tank
3. Drain most of the water, leave the fish in, and stop the crack from spreading
4. Put both fish in the same bucket until the next morning

AnswerB. Unplug the heater and filter, transfer the tank water and media into the storage boxes, house the oscars one per box with the heater and air pump, and empty the tank

ExplanationA lengthening crack is the prelude to a burst; a 120 cm tank bursting means flood damage, electric shock and total loss of fish. First cut the power to prevent the heater running dry as the level drops and any electrical leakage, transfer the tank water to the storage boxes to preserve pH and temperature, and add the media to maintain the bacteria. Oscars fight, so house them one per box, secure warmth and oxygen with the heater and air pump, and empty the tank. Tape will not stop a crack. Draining the water and leaving the fish causes oxygen shortage and temperature drop in shallow water, and the remaining pressure still advances the crack. The same bucket is dangerous from fighting and oxygen shortage. From the next day, return the tank water and media to a new tank and restart.

IssuesThe aging of the tank glass and any warping of the base were not inspected. Having large emergency containers was good, but there was no provision for housing two large fish separately.

ImprovementInspect the tank glass and seams monthly and check the stand is level. For large fish, keep enough evacuation containers, heaters and air pumps for each fish. Write the emergency procedure (power, tank water, media, fish) on paper and keep it beside the tank.

April. While cleaning the substrate of a 60 cm tank, a small Lake Tanganyika cichlid (4 cm) was sucked into the siphon hose and dropped into the drain bucket. The bucket holds dirty tank water. The fish is on its side at the bottom of the bucket, gills moving. A few scales on its flank have come off.

Which is the most appropriate first action?

1. Rinse it under the tap right away and return it to the tank
2. It is on its side, so judge it cannot be saved and leave it
3. Grab it in your hand and throw it into the tank
4. Gently scoop it up with a container, bucket water and all, return it to the tank, observe it where the current is gentle, and add a slime-coat protectant at the recommended dose

AnswerD. Gently scoop it up with a container, bucket water and all, return it to the tank, observe it where the current is gentle, and add a slime-coat protectant at the recommended dose

ExplanationA fish sucked through a hose has its slime coat and scales damaged by pressure and impact, but if the gills are moving there is room for recovery. Scoop it up in a container with the bucket water, return it gently to a spot in the tank with gentle current, observe, and add a slime-coat protectant at the recommended dose to protect the wounds. The bucket water is tank water, so returning it as is causes no problem. Rinsing under the tap is fatal from chlorine and temperature difference. Lying on its side is often shock from the impact, and many recover within hours. Grabbing and throwing adds impact and slime-coat damage. From the next day, if white cotton appears on the scale loss or the fish still swims tilted, consult a fish-savvy shop or hospital the same day.

IssuesA hose with no guard on the intake was used in a tank with small fish, and cleaning was done without watching where the fish were. The habit of fish approaching the intake during cleaning was not anticipated.

ImprovementFit a net or sponge on the substrate siphon's intake. Watch where the fish are while moving the intake, and use a weaker siphon when small fish or fry are present. Keep a slime-coat protectant on hand for use right after an accident.

June. A 27 cm oscar in a 120 cm tank took in a large piece of gravel with its food, and it is lodged at the back of the mouth where it cannot be spat out. The fish shakes its head with its mouth open and works its gill covers hard, looking distressed. The substrate is 1–2 cm gravel, and the fish has previously been seen taking it into its mouth and spitting it out.

Which is the most appropriate first action?

1. Support the fish underwater with wet hands; if the gravel is visible with the mouth open, gently remove it with blunt-tipped tweezers, and if not visible consult a fish-treating hospital the same day
2. Leave it to spit it out on its own
3. Take the fish out of the water, hold it upside down and tap it to knock it out
4. Push a finger deep into the mouth and shove it down

AnswerA. Support the fish underwater with wet hands; if the gravel is visible with the mouth open, gently remove it with blunt-tipped tweezers, and if not visible consult a fish-treating hospital the same day

ExplanationGravel stuck in the mouth blocks breathing and feeding, and if gill movement stops the fish suffocates. Support the fish underwater with wet hands and, if the gravel is in a visible position inside the mouth, gently remove it with blunt-tipped tweezers. If it is not visible, is deep in, or the fish struggles, do not force it; consult a fish-treating animal hospital the same day. Leaving it means suffocation within minutes if gill movement stops. Taking the fish out and tapping it upside down is dangerous from slime-coat damage and impact. Pushing with a finger lodges it in the esophagus or stomach. Afterwards, isolate the fish to rest, withhold food until the next day, and watch mouth movement and both gills. To prevent recurrence, change the substrate to rocks too large for the mouth or fine sand that can be passed.

IssuesGravel small enough to fit in the mouth was used as substrate, and the fish had been seen taking it in without any countermeasure. The owner did not know oscars habitually take gravel into their mouths.

ImprovementFor large cichlids, use substrate of large rocks that cannot fit in the mouth or fine sand that can be passed if swallowed. Do not place decorations that fit in the mouth. Check the mouth and breathing after feeding and keep tweezers and a quarantine container ready to act at once.

February. Four angelfish in a 60 cm tank developed ich, so a fish medication was added. Without reading the instructions or measuring, about five times the recommended dose was poured in by eye. An hour later all are lying on the bottom moving their gills rapidly. One is belly-up. The water is deeply colored. There are 20 L of dechlorinated stock water at the same temperature.

Which is the most appropriate first action?

1. It is proof the medication is working, so wait as is
2. Add more medication to cure the ich in one go
3. Move all the fish to a bucket of tap water to wash off the medication
4. Do a 50% water change with same-temperature, same-pH water to lower the concentration, put activated carbon in the filter, turn aeration to maximum, and observe

AnswerD. Do a 50% water change with same-temperature, same-pH water to lower the concentration, put activated carbon in the filter, turn aeration to maximum, and observe

ExplanationFish medication becomes toxic to the fish themselves above the recommended dose; lying down with rapid breathing is poisoning. Do a 50% water change with same-temperature, same-pH water to lower the concentration, put activated carbon in the filter to absorb the medication, and turn aeration to maximum to secure oxygen. After one hour there is a chance of recovery. Lying down is poisoning, not effect; waiting means death. Adding more is fatal. Tap water adds a further blow from chlorine and sudden change. Continue the carbon the next day, and after recovery redo the ich treatment at the recommended dose in a separate container. If fish stay down for hours or the belly-up fish stops responding, consult a fish-savvy shop or hospital the same day.

IssuesThe medication's instructions were not read and it was poured in by eye without measuring. There was no awareness that the drug is toxic to fish too, and a mistaken belief that more is better.

ImprovementCalculate the water volume and measure the recommended dose accurately with a measuring spoon or dropper. Medicate in a separate container if possible rather than the main tank. Keep activated carbon on hand to respond at once to a dosing accident. Record each dose with date and amount.

8 p.m. in January. A local power outage has stopped the heater, filter and air pump. Twelve mbuna in a 90 cm tank, water 26°C, and the room temperature is starting to fall with the heating off. When power will return is unknown. On hand: polystyrene foam board, blankets, a battery-powered air pump, disposable hand warmers, and a gas stove for boiling water.

Which is the most appropriate first action?

1. Cover the tank with foam board and blankets, run the battery air pump for oxygen, float bottles of hot water if the temperature drops, and stop feeding
2. Put disposable hand warmers in the water to warm it
3. Pour hot water directly into the tank to maintain the temperature
4. Just wait for power to return and do nothing

AnswerA. Cover the tank with foam board and blankets, run the battery air pump for oxygen, float bottles of hot water if the temperature drops, and stop feeding

ExplanationDuring an outage the priorities are keeping warm and securing oxygen. Cover the tank with foam board and blankets to limit heat loss and run the battery air pump for oxygen. When the temperature starts to fall, float plastic bottles of hot water to add heat a little at a time. Stop feeding, since food fouls the water and consumes oxygen. Hand warmers do not work underwater and leak their contents. Pouring hot water in directly causes localized sudden change and burns. If nothing is done, the water sealed inside the filter goes foul and floods in when power returns, so after a long stop discard the filter's water before restarting. If the temperature falls to 20°C or below or fish lie on their sides, seek advice the same day once power is back.

IssuesA battery air pump was on hand for outages, but no warming procedure had been decided, leaving the owner unsure. The risk of restarting the filter after a stop was also not understood.

ImprovementFor winter outages, store foam board, blankets, a battery air pump and bottles for hot water as a set. Write the outage procedure (cover, oxygen, hot-water bottles, stop feeding, discard filter water on restart) on paper and keep it beside the tank.

A March night. A major earthquake struck; 30% of the water sloshed out of the 60 cm tank but the tank is intact. The four angelfish are swimming. The power is out and the municipality has issued an evacuation order to the shelter. Tanks cannot be brought into the shelter. On hand: a lidded bucket, a battery air pump, plastic bags and a blanket. The house may collapse in aftershocks.

Which is the most appropriate response to this situation?

1. Leave the fish behind and release them in a nearby river to survive
2. Move the fish with their tank water into the lidded bucket, add the battery air pump, wrap it in the blanket for warmth, take it along, and look for a shop or acquaintance near the shelter who can hold them
3. Do not evacuate; stay beside the tank to protect the fish
4. Carry the tank to the shelter

AnswerB. Move the fish with their tank water into the lidded bucket, add the battery air pump, wrap it in the blanket for warmth, take it along, and look for a shop or acquaintance near the shelter who can hold them

ExplanationHuman life comes first; once an evacuation order is issued you must not stay. Moved into a lidded bucket with their tank water, with the battery air pump for oxygen and a blanket for warmth, the fish can be kept for several days. Look for a shop, acquaintance or pet-friendly place near the shelter to hold them. Releasing them violates the Invasive Alien Species Act and local ordinances, and foreign cichlids can disrupt the ecosystem of Japanese rivers. Staying in a house that may collapse is life-threatening. A full tank is heavy, fragile and cannot be carried. Once home, discard the filter's water before power is restored, top up with same-temperature water, and restart.

IssuesNo plan had been made for how to carry the fish out in a disaster, nor was it anticipated that tanks are not allowed in shelters. There was also little awareness that releasing fish is illegal and destroys ecosystems.

ImprovementKeep a disaster carry-out kit for the fish (lidded bucket, battery air pump, blanket, dechlorinator) near the tank. Confirm in advance a shop or acquaintance who can hold the fish. Secure the tank with anti-seismic mats and tip-over prevention, and keep the water level below the lid to reduce spillage from shaking.

July. Returning in the evening from a three-day trip, the 90 cm tank in the room with the air conditioning switched off reads 32°C; two of the ten mbuna are gasping at the surface and one is lying on its side. The automatic feeder kept dispensing twice a day and leftover food has built up on the bottom. The water is slightly cloudy. An electric fan and aeration equipment are available.

Which is the most appropriate first action?

1. Add a lot of ice to bring it straight down to 26°C
2. First add food to make up for three days of poor nutrition
3. Turn aeration to maximum, siphon out the leftover food, do a 1/3 water change with same-temperature water, aim the fan at the surface to lower the temperature 1–2°C at a time, and isolate the fish on its side
4. Judge the fish on its side to be dead, remove it, and leave the rest

AnswerC. Turn aeration to maximum, siphon out the leftover food, do a 1/3 water change with same-temperature water, aim the fan at the surface to lower the temperature 1–2°C at a time, and isolate the fish on its side

ExplanationThis is oxygen shortage and ammonia from high temperature combined with rotting leftover food. First turn aeration to maximum to secure oxygen, siphon out the leftover food, and do a 1/3 water change with same-temperature water to dilute the waste. Aim the fan at the surface to lower the temperature 1–2°C at a time, and keep the fish on its side in a quarantine container, dark and quiet. Rapid cooling with ice is fatal from temperature shock. Adding food increases waste and worsens oxygen shortage; fish are fine without eating for several days. Even lying on its side, a fish with moving gills has room to recover, so do not give up. Test ammonia and nitrite again tomorrow and keep changing water. If a fish stays on its side or its gills are dark red, consult a fish-savvy shop or hospital the same day.

IssuesThe air conditioning was switched off during a summer absence with no cooling or aeration in place. The automatic feeder was not adjusted and was left set to a quantity that accumulates leftovers.

ImprovementWhen away in summer, run the air conditioner in the tank's room or keep a cooling fan and aeration running constantly. Set the automatic feeder to a small amount and test it beforehand. For an absence of a few days the fish are fine without food, so either skip feeding or ask family or a friend.

November. While rearranging the mbuna rockwork bare-handed, the owner scraped the back of a hand on a rock. Two weeks later a hard reddish-purple lump formed at that spot, growing slowly and beginning to spread toward the elbow as a line of bumps. Pain is mild and there is no fever. Over-the-counter antiseptic applied daily has not helped. The fish in the tank show nothing abnormal.

Which is the most appropriate response to this situation?

1. It is mild, so keep disinfecting and wait for it to heal naturally
2. Lance the lump with a needle and squeeze out the contents
3. See a dermatologist, explain the contact with tank water, and from now on wear gloves for tank work whenever you have a cut on your hand
4. The fish are the cause, so reset the tank and give up the fish

AnswerC. See a dermatologist, explain the contact with tank water, and from now on wear gloves for tank work whenever you have a cut on your hand

ExplanationA reddish-purple lump that appears weeks after a wound contacted tank water or rocks and then spreads is the classic course of a nontuberculous mycobacterial infection (fish tank granuloma). Ordinary antiseptic does not cure it; telling a dermatologist about the tank work speeds diagnosis and leads to appropriate treatment. Natural healing cannot be expected and it spreads if left. Lancing with a needle spreads the infection. The bacteria can be present in the water even when the fish show no symptoms, so there is no need to give up the fish, but always wear gloves for tank work when you have a cut and make a habit of washing with soap afterwards. People with weakened immunity or diabetes should take particular care and see a doctor early.

IssuesThe rockwork was handled bare-handed and tank work continued with an open scrape. The owner did not know that aquarium-related skin infections exist and did not seek care until the lump was spreading.

ImprovementMake long rubber gloves the rule for tank work and avoid working when you have a cut on your hand. Wash hands and arms with soap afterwards. If a wound or lump that will not heal appears after tank work, see a dermatologist early and mention the aquarium exposure.

April. While trying to move a 20 cm flowerhorn bare-handed, a hard dorsal spine was driven deep into the base of the index finger. It is bleeding and throbbing. The tank has not had a water change for two weeks. Antiseptic and adhesive bandages are available. The fish was moved safely, but the finger is starting to swell a little.

Which is the most appropriate response to this situation?

1. Wash the wound thoroughly under running water right away and disinfect it; see a dermatologist or surgeon promptly if swelling, redness or fever develops
2. Seal it with an adhesive bandage and do nothing
3. Soak the finger in the tank water to cool it
4. Suck the wound to draw out the poison

AnswerA. Wash the wound thoroughly under running water right away and disinfect it; see a dermatologist or surgeon promptly if swelling, redness or fever develops

ExplanationA cichlid's dorsal spines are hard, and a deep puncture carries bacteria from dirty tank water deep into the wound. Wash the wound thoroughly under running water right away, disinfect, and keep it clean. Deep punctures readily become infected inside; if swelling, redness, fever or pus develops, see a dermatologist or surgeon promptly and say the injury happened during tank work. Sealing alone traps bacteria inside. Soaking in tank water adds more bacteria. Sucking the wound puts mouth bacteria into it and tank-water bacteria into your mouth. From now on do not hold large fish bare-handed; move them in water with a container. The fish may have damaged its slime coat while struggling in pain, so check its skin the next day as well.

IssuesA large cichlid with hard spines was handled bare-handed. The injury happened at a tank unchanged for two weeks, a high-risk situation for bacteria entering deep into the wound.

ImprovementMove large cichlids in water with a container or bowl, never with a net or bare hands. Wear thick rubber gloves when working. Share the puncture-wound procedure (running water, disinfect, monitor, when to see a doctor) with the family and keep a first-aid kit near the tank.

May. Angelfish and mbuna are kept separately in two 60 cm tanks. The angelfish tank has ich and is under treatment, but the same net and bucket were used to clean both tanks. This morning one white spot is visible on one of the mbuna. There is no disinfecting equipment, and the net was just rinsed in tap water after use.

Which is the most appropriate response to this situation?

1. It is only one spot, so do nothing to the mbuna tank
2. Mix the water of both tanks to even out the conditions
3. Add double the recommended dose of fish medication to the mbuna tank as a preventive
4. Dedicate equipment to each tank, disinfect anything that was shared with boiling water or drying, and act early in the mbuna tank with heating and water changes

AnswerD. Dedicate equipment to each tank, disinfect anything that was shared with boiling water or drying, and act early in the mbuna tank with heating and water changes

ExplanationThe ich parasite and bacteria travel between tanks on nets, buckets and hoses. A rinse in tap water does not remove them, and touching a healthy tank with equipment from a tank under treatment makes carry-over unavoidable. Dedicate equipment to each tank and disinfect anything shared with boiling water or complete drying. Treat even one spot in the mbuna tank as early infection and act promptly with heating of 1–2°C per day and a 1/3 water change. Left alone it spreads through the tank within days. Mixing water transfers pathogens directly. Preventive double-dosing is poison to fish and bacteria. Work on the healthy tank first and the sick tank last, and wash hands afterwards. If it spreads, consult a fish-savvy shop or hospital the same day.

IssuesEquipment was shared between multiple tanks, carrying pathogens from the sick tank to the healthy one. The owner mistakenly believed that rinsing the net in tap water was disinfection.

ImprovementColor-code and dedicate a net, bucket and hose to each tank. Do the sick tank's work last and disinfect equipment with boiling water or complete drying. Wash hands before and after work and double-check before touching another tank.

August. An oscar with dropsy died in a 90 cm tank. It was removed bare-handed, the quarantine container's water was poured down the kitchen sink, and the container and the dishes were washed with the same sponge. Then dinner preparation began without washing hands. There are a toddler and an elderly person in the home. The dead fish was put in a trash bag.

What is wrong with this behavior, and what is the most appropriate response going forward?

1. There is no problem. Fish water is clean, so pouring it down the kitchen sink is fine
2. Burying the dead fish in the garden solves the hygiene problem
3. Tank water contains bacteria, so never pour it in the kitchen, dedicate equipment, and wash hands with soap after work. Clean and disinfect the sink and sponge that were used
4. The toddler and elderly person cannot be infected as long as they do not go near the fish

AnswerC. Tank water contains bacteria, so never pour it in the kitchen, dedicate equipment, and wash hands with soap after work. Clean and disinfect the sink and sponge that were used

ExplanationTank water and sick fish can carry bacteria that infect people, such as Salmonella, Aeromonas and nontuberculous mycobacteria. Pouring the water in the kitchen contaminates dishes and food, with a risk of infection for people with weak immunity such as toddlers and the elderly. Dispose of tank water in the bathroom, toilet or outdoors, dedicate containers and sponges to the tank, and wash hands with soap after work. Wash the sink and sponge used this time with detergent and disinfect with boiling water or chlorine bleach. Burying in the garden does not solve the kitchen contamination. Pathogens travel via water and equipment, so keeping the toddler away from the fish is not enough. Dispose of the dead fish as burnable waste following municipal instructions.

IssuesTank water was mistaken for clean, poured down the kitchen sink, and a dish sponge was shared. The sick fish was handled bare-handed and cooking began without hand washing. There was no awareness of immunocompromised family members in the home.

ImprovementMake a family rule never to pour tank water in the kitchen. Color-code a tank-only sponge and bucket and never bring them into the kitchen. Always wash hands after work and handle sick fish with rubber gloves. Keep toddlers from touching tank water.

7 a.m. in September. All twelve mbuna in a 90 cm tank are crowded near the surface, mouthing hard. One is drifting on its side. The water is slightly cloudy and smells. Yesterday ten newly bought fish were added all at once. The filter is running but there is no aeration. Test strips show both ammonia and nitrite.

Which is the most appropriate first action?

1. Everyone is gasping, so judge it to be disease and add fish medication
2. Give the morning feed to calm them
3. Evacuate all the fish to a bucket of tap water
4. Do a 1/3 to 1/2 water change with same-temperature, same-pH water, add aeration, stop feeding, isolate the fish on its side, and repeat testing and water changes every few hours

AnswerD. Do a 1/3 to 1/2 water change with same-temperature, same-pH water, add aeration, stop feeding, isolate the fish on its side, and repeat testing and water changes every few hours

ExplanationAdding ten fish at once exceeded the bacteria's processing capacity; ammonia and nitrite spiked, causing oxygen shortage and poisoning in all the fish. Life support for the fish is improving the water itself. Do a 1/3 to 1/2 water change with same-temperature, same-pH water to dilute the toxins, add aeration to secure oxygen, and stop feeding to avoid adding waste. Isolate the fish on its side to rest, and repeat testing and water changes every few hours. The cause is water quality, so medication is pointless and burdens weakened fish. Food increases oxygen consumption and waste. Tap water adds a further blow from chlorine and pH difference. Test daily for several days until ammonia and nitrite settle, and consult a fish-savvy shop or hospital the same day for any fish that stays on its side.

IssuesTen fish were added at once without considering the bacteria's capacity, and overcrowding caused a sudden water-quality crash. There was no aeration and no preparation for the oxygen-shortage sign of fish crowding at the surface.

ImprovementAdd fish a few at a time, several weeks apart, and test ammonia and nitrite daily for a week after each addition. Run aeration constantly. Always keep dechlorinated, same-temperature stock water ready for an immediate water change in a crisis.

A December morning. An oscar (25 cm) with dropsy symptoms is to be driven 40 minutes to a fish-treating animal hospital. Outside temperature is 5°C. On hand: thick plastic bags, a polystyrene foam box, an air pump, disposable hand warmers and a bucket. The hospital has said, "Please bring it in its tank water."

Which is the most appropriate way to transport this fish?

1. Put tap water in a bag with the fish and set it on the seat of the heated car
2. Put tank water in a bag at a depth that keeps the fish from lying on its side, leave plenty of air, tie it off, place it in the foam box with hand warmers stuck on the outside, and carry it in the dark
3. Fill the bucket to the brim with tank water and carry it without a lid
4. Put a hand warmer directly inside the bag to keep it warm

AnswerB. Put tank water in a bag at a depth that keeps the fish from lying on its side, leave plenty of air, tie it off, place it in the foam box with hand warmers stuck on the outside, and carry it in the dark

ExplanationTransport stress can be fatal to a sick fish, so the top priority is not changing its environment. Put tank water in a bag at a depth that keeps the fish from lying on its side, leave plenty of air and tie it off to secure oxygen, and place it in a foam box kept dark and warm. Stick hand warmers on the outside of the box or where they do not touch the bag to avoid localized heating. Tap water shocks a sick fish with chlorine and pH difference. A brim-full bucket spills with motion, has no air layer so oxygen runs short, and the fish can jump out. A hand warmer in the bag causes localized overheating with burns and sudden change. Bring the pH, temperature and water-quality readings, diet, water-change history and photos of the symptoms to the appointment, and report the condition of tankmates too.

IssuesTransport had not been thought through in advance, and the reason for using tank water and how to keep it warm were not understood. The information for the hospital (readings, photos) was also not prepared.

ImprovementFind a fish-treating hospital in advance and keep a transport kit (thick bags, foam box, air pump, hand warmers) on hand. Record daily water quality and pH so they can be shown at the appointment. Make a habit of recording symptoms in photos and video.

A May morning. A mbuna (8 cm) was found on the floor and returned to the tank with wet hands. Its body is still damp, but once in the water the gill covers do not move and it sinks lying on its side. The eyes are not sunken. How long it has been out is unknown, but the water marks on the floor have not dried. The tank has aeration.

Which is the most appropriate first action?

1. The gills are not moving, so judge it dead and remove it right away
2. Take it out of the water and press its chest for cardiac massage
3. Hold it against the strong filter outlet to stimulate it
4. Support it by hand near the aeration with its head upstream, move it slowly back and forth to pass water over the gills, and keep going for tens of minutes waiting for a response

AnswerD. Support it by hand near the aeration with its head upstream, move it slowly back and forth to pass water over the gills, and keep going for tens of minutes waiting for a response

ExplanationCardiac massage is not realistic for a fish; resuscitation means passing water over the gills so it can take in oxygen. Support it by hand near the aeration with its head upstream and move it slowly back and forth to push water through the gills. If the water on the floor has not dried, not much time has passed since the fall and recovery is possible. Keep going for tens of minutes and wait for the gill covers or body to move again. Motionless gills do not necessarily mean immediate death; giving up is too hasty. Taking it out of the water and pressing its chest causes suffocation and organ damage. A strong outlet topples a weakened fish and exhausts it. Once it responds, rest it where the current is gentle, add a slime-coat protectant at the recommended dose, and observe for several days.

IssuesThe lid did not adequately prevent jumping, and by discovery enough time had passed for the gills to stop. Not knowing that fish resuscitation means passing water over the gills could have led to hesitation.

ImprovementPrevent jumping with a heavy glass lid and gap covers. Share the fish resuscitation procedure (water over the gills, head upstream, wait tens of minutes) with the family. Make a habit of checking the lid position and water level at night and before going out.

Midnight on Saturday. One mbuna in a 90 cm tank has a swollen belly and white stringy feces, is breathing fast and sits motionless behind a rock. The fish-treating animal hospital does not open until 9 a.m., and the emergency (after-hours) animal hospital does not accept fish. A quarantine container, heater and air pump are available. The other fish in the main tank are swimming normally.

Which is the most appropriate response to this situation?

1. Keep calling the after-hours emergency hospital and insisting they see it like a dog or cat
2. Move it to a quarantine container at the same temperature and pH as the main tank, stop feeding, keep it dark and quiet, stop feeding the main tank too, and contact the fish-treating hospital first thing in the morning
3. Do nothing until morning and watch in the main tank
4. Add fish medication to the main tank even at midnight to treat everything

AnswerB. Move it to a quarantine container at the same temperature and pH as the main tank, stop feeding, keep it dark and quiet, stop feeding the main tank too, and contact the fish-treating hospital first thing in the morning

ExplanationWith suspected Malawi bloat, the best an owner can do at night is isolate the sick fish and stabilize its environment. Move it to a quarantine container at the same temperature and pH as the main tank, stop feeding, and keep it dark and quiet to reduce gut load and stress. The other fish in the main tank may be pre-symptomatic, so stop feeding them too, watch their feces, and contact the fish-treating hospital first thing in the morning. Most after-hours emergency hospitals cannot treat fish, and repeated calls only waste time. Left in the main tank, the sick fish weakens and stresses its tankmates. Dosing the main tank at midnight without a diagnosis burdens the filter and other fish and makes the morning diagnosis harder. Record the symptoms in photos and video.

IssuesThe fish-treating hospital's hours and after-hours contacts had not been looked up in advance, causing panic at midnight. The early sign of bloat was missed during the day, so discovery came at midnight.

ImprovementPost the contacts and hours of a fish-treating animal hospital and a specialist shop beside the tank. Decide in advance that at night the plan is isolation and a stable environment until morning. Check feces and belly shape at morning and evening feedings, and seek advice about anything abnormal during the day.

February. Two oscars in a 120 cm tank. In a fight, the smaller one received a deep bite on its flank and blood keeps streaming out in a thread through the water. Several scales are gone and white flesh is showing. The fish can swim but the larger one keeps chasing it. A quarantine container, a divider and salt are available. Water 27°C.

Which is the most appropriate first action?

1. Press the wound with a finger to stop the bleeding by pressure
2. Watch in the main tank until the bleeding stops
3. Immediately move the losing fish to a quarantine container to rest, give a 0.3–0.5% salt bath in clean water, and if the bleeding continues consult a fish-treating hospital the same day
4. Apply a human styptic to the wound

AnswerC. Immediately move the losing fish to a quarantine container to rest, give a 0.3–0.5% salt bath in clean water, and if the bleeding continues consult a fish-treating hospital the same day

ExplanationBleeding in a fish cannot be stopped by pressure underwater; the first step is getting it away from the attack and at rest so blood flow settles. Immediately move the losing fish to a quarantine container and give a 0.3–0.5% salt bath in clean water to prevent secondary infection. If bleeding has not stopped after hours, there is bleeding from the gills, or it swims tilted, consult a fish-treating animal hospital the same day. Pressing the wound with a finger damages slime coat and scales, and the fish struggles and bleeds more. Watching in the main tank means continued chasing and exhaustion. A human styptic washes off underwater and its ingredients are harmful to fish. After isolation, keep the water clean with daily 1/3 changes and watch for white cotton or pinecone scales. The fundamental solution for two oscars is separate tanks.

IssuesTwo aggressive oscars were kept in the same tank and not separated until there was a wound. Not knowing that pressure cannot stop bleeding in fish could have led to hesitation.

ImprovementKeep multiple oscars in separate tanks or partitioned with a permanent divider. Keep a quarantine container and salt on hand and make it a habit to isolate the day a wound is seen. Understand that stopping bleeding in fish comes down to isolation, rest and clean water.