Shrimp & crabs case method: 50 questions

7 a.m. in April. One of 12 cherry shrimp in a 20 L tank is lying on its side on the substrate. On closer look, half of the old shell on its back is still peeled up and attached; it only twitches its legs now and then and cannot swim. Last night the water looked a little cloudy, so you did a larger-than-usual 50% water change. The other shrimp are grazing on algae on the moss as usual.

What is the most appropriate first action for this animal?

1. Gently peel off the remaining shell with tweezers to help it finish molting
2. Do not touch it; place it beside a hiding spot, keep the tank dark and quiet, add mineral supplement at the recommended dose and watch until the next day
3. It is weak, so move it to a separate container of fresh tap water and keep it warm
4. Observe it while frequently repositioning it with a net so the other shrimp cannot pick at it

AnswerB. Do not touch it; place it beside a hiding spot, keep the tank dark and quiet, add mineral supplement at the recommended dose and watch until the next day

ExplanationMolting failure is often triggered by sudden changes in water quality or osmotic pressure, such as a large water change. Peeling off the shell by hand tears the soft body and is usually fatal, so never do it. The correct answer is not to touch it, place it by a hiding spot in a dark, quiet environment, add mineral supplement at the recommended dose, and watch until the next day. Tap water with residual chlorine is lethal, and shrimp do not need warming. Moving it repeatedly with a net causes limb loss and exhaustion. If it cannot move for more than a day, contact a hospital that treats invertebrates (a call-now sign).

IssuesPanicking over cloudy water, the owner did a 50% water change that abruptly changed the water chemistry and triggered the molting failure. They lacked the knowledge that shrimp need small changes of 1/4 or less, and the rule never to interfere with a molting animal.

ImprovementChange 1/4 or less once a week using dechlorinated water at the same temperature. Keep food and supplements containing minerals and calcium on hand, and provide more moss and ceramic tubes than there are shrimp for molting cover. If you see signs of an upcoming molt (inactivity, not eating), postpone the water change.

3 p.m. in early August. You keep 8 Amano shrimp in a 30 cm tank in a room without air conditioning. The thermometer reads 29°C. For two days the abdominal muscle of one shrimp has been turning white and opaque; today it is sluggish and not eating algae. Two others also look faintly white in the abdomen. The water is slightly cloudy and leftover food has settled on the bottom.

When white muscle disease (muscle necrosis) is suspected, what is the most appropriate response?

1. Add a fish ich medication at half the recommended dose and observe
2. Put ice directly into the tank to drop the temperature to 22°C at once
3. Use a cooling fan and a frozen water bottle to lower the temperature 1°C per hour to 25°C or below, stop feeding and add aeration
4. Remove only the white shrimp and let them recover in a small container on a sunny windowsill

AnswerC. Use a cooling fan and a frozen water bottle to lower the temperature 1°C per hour to 25°C or below, stop feeding and add aeration

ExplanationWhite muscle disease is caused by high water temperature and poor water quality and kills within days. Fish medications are lethal to shrimp and must not be used. Chilling with ice causes a sudden temperature swing that triggers molting failure or shock, so lower the temperature gradually, 1°C per hour. Stop feeding to prevent further water fouling and add aeration to offset the low oxygen of warm water. A small container on a windowsill gets even hotter and worsens things. Animals whose whitening progresses should be discussed with an invertebrate-treating hospital the same day, but fixing the environment comes first.

IssuesThe owner neglected summer temperature control in a room without air conditioning and was slow to notice the dangerous 29°C. Leftover food was left to foul the water. They lacked the knowledge that shrimp need 25°C or below and the habit of checking temperature daily.

ImprovementInstall a cooling fan or chiller from June, check the thermometer daily and keep the water at 25°C or below. Feed less in summer and remove leftovers immediately. Avoid overcrowding and prepare heat-wave measures (frozen bottles, shade, room air conditioning) in advance.

10 p.m., three days after adding 15 cherry shrimp to a tank you set up only a week ago because you could not wait. The shrimp, fine until the evening, have left their hiding places and are clustered on the glass near the surface, legs twitching. A few lie motionless on the bottom. You have not yet bought a water test kit.

What is the most appropriate first action?

1. Change 1/3 of the water with dechlorinated water at the same temperature, increase aeration and stop feeding
2. Assume low oxygen, feed less and watch until morning
3. Add an extra-large dose of bacteria starter to mature the water overnight
4. Move them all into a cup of tap water and wash the tank tomorrow

AnswerA. Change 1/3 of the water with dechlorinated water at the same temperature, increase aeration and stop feeding

ExplanationIn a newly set-up tank the filter bacteria are immature and ammonia and nitrite spike. Gathering at the surface with twitching legs is a classic poisoning sign; left alone, the whole colony can die overnight. The correct answer is to change water with dechlorinated water at the same temperature to dilute the toxins, add aeration for oxygen, and stop feeding to reduce the pollution source. Bacteria starter does not act quickly, and tap water is lethal because of chlorine. Waiting until morning is dangerous; check values with a test kit the next day and repeat water changes as needed.

IssuesThe owner ignored the rule of waiting one month after setup and added shrimp without a test kit. They did not appreciate that shrimp are more sensitive to water quality than fish and had no way to measure it.

ImprovementGrow the bacteria for at least one month after setup before adding shrimp. Buy ammonia and nitrite test kits beforehand and test at least weekly for the first month after introduction. Always keep a stock of dechlorinated water for emergency changes.

An October evening. Your land hermit crab, in its third year in a 45 cm tank, buried itself in the sand two weeks ago and has not come out. The hygrometer reads 75% and a panel heater keeps the tank at 26°C. The fruit in the food dish is untouched. You are worried it may have died and feel tempted to dig up the sand to check. Its tankmate is walking on the climbing wood as usual.

What is the most appropriate response?

1. Gently dig up the sand, check whether it is alive and bring it, shell and all, onto the surface
2. Assume it is molting, never dig, keep temperature and humidity steady and wait while replacing food and water dishes
3. Pour seawater from the dish onto the sand to moisten it and encourage it to come out
4. Remove the tankmate and move the tank to a bright spot to observe

AnswerB. Assume it is molting, never dig, keep temperature and humidity steady and wait while replacing food and water dishes

ExplanationLand hermit crabs bury themselves to molt and may stay under for several weeks to over a month. During a molt the body is extremely soft, and digging it up kills it through drying or injury, so never dig. The correct answer is to maintain temperature and humidity and wait quietly, replacing food and both water dishes daily. Pouring water on the sand collapses the molting chamber, and moving the tank to a bright spot adds stress. If it has been under more than a month and a half and there is a foul smell on the sand, consult a hospital.

IssuesThe owner did not know hermit crabs bury themselves for long periods to molt and nearly dug it up thinking it was dead. They lacked the knowledge that digging up a molting animal is the most common cause of death in land hermit crab keeping.

ImprovementMaintain moist coral sand at least 10 cm deep for burrowing and note the date when it goes under. To protect a molting animal from a tankmate, provide several hiding places or have a separate container ready for temporary isolation.

A weekend in March. While cleaning, you replaced half the water in a 20 L tank with somewhat cold tap water treated with dechlorinator. The next morning, 5 of 10 cherry shrimp had molted, and 2 of them died mid-molt. The rest are sluggish. The water temperature has dropped from 22°C the day before to 18°C.

What should you do right now to protect the survivors?

1. Change another half of the water with fresh water to restore water quality
2. Raise the temperature to 25°C at once with a heater to speed recovery
3. Return the temperature to 22°C at 1°C per hour, stop further water changes, add hiding places and watch quietly
4. Move all the remaining shrimp to a new, separate tank

AnswerC. Return the temperature to 22°C at 1°C per hour, stop further water changes, add hiding places and watch quietly

ExplanationA large water change combined with a sudden 4°C temperature drop triggered mass molting, and the shrimp are dying of molting failure. The correct answer is to stop the sudden changes: return the temperature gradually, hold off on water changes to stabilize the water, and add places for molting shrimp to hide. Another water change causes yet another sudden shift, and rapid heating is a further shock. Moving them to a new tank adds a water-chemistry difference on top. If deaths continue the next day, seek advice the same day.

IssuesShrimp water changes should be 1/4 or less at the same temperature, yet half the water was replaced with cold water. The owner did not know that sudden temperature and water-quality changes trigger molting and upset the tank's stability for cleaning convenience.

ImprovementChange 1/4 or less once a week, checking with a thermometer that the water is the same temperature and adding it slowly. Draw the water the day before and let it reach room temperature. Spread cleaning tasks out; do not do a large substrate cleaning and water change on the same day.

A June morning. Your Japanese freshwater crab, kept alone in a 30 cm tank, has molted. But three days later its carapace is still soft and floppy and it moves weakly. You feed only fish food every other day and change the water daily with dechlorinated tap water. After previous molts the shell hardened by the next day.

What is the most likely cause, and what should you do?

1. Suspect calcium deficiency: offer dried sardines, leave the molted shell for it to eat, add mineral supplement and watch without handling
2. Put it on dry land in sunlight to harden the shell
3. The water is too cold, so heat it to 30°C to boost metabolism
4. While waiting for the shell to harden, crush a human calcium tablet and dissolve it in the water

AnswerA. Suspect calcium deficiency: offer dried sardines, leave the molted shell for it to eat, add mineral supplement and watch without handling

ExplanationHardening the new shell requires calcium and minerals, which fish food alone often lacks. The correct answer is to offer a calcium source such as dried sardines, leave the molted shell for a few days to be eaten, use a shrimp/crab mineral supplement at the recommended dose, and not handle it while soft. Sunbathing is dangerous due to drying and heat. Freshwater crabs need 18–25°C; 30°C is lethal. Human supplements have unknown composition and concentration and ruin water quality. If the shell has not hardened and it is not eating after a week, consult a hospital.

IssuesThe diet was fish food only, with no thought given to calcium and mineral supplementation. The molted shells were probably being thrown away. The owner did not understand that a molt is only complete once the nutrients to harden the shell are available.

ImprovementRotate dried sardines, vegetables and crab food, and leave molted shells for a few days. Keep mineral supplement on hand, and when signs of molting appear (reduced appetite, hiding), prepare land and hiding areas. Record molt dates and the days taken to harden.

8 a.m. in January. In the living-room tank, your land hermit crab has left its shell and is huddled naked on the sand, not moving. The heating was switched off last night and the room is 15°C; the panel heater is on but the hygrometer reads 45%. Its body surface is dry and dull, and its legs move slightly when touched. Three spare shells are in the tank.

What is the most appropriate first action?

1. Push its body back into its original shell
2. Raise humidity with a mister and warm the tank, place it on moist sand with several shells beside it, keep dark and quiet, and consult a hospital today if it does not move
3. Submerge it in the water dish to rehydrate it
4. Wrap it in plastic wrap to prevent drying and put it somewhere warm

AnswerB. Raise humidity with a mister and warm the tank, place it on moist sand with several shells beside it, keep dark and quiet, and consult a hospital today if it does not move

ExplanationLand hermit crabs breathe with gills on land and need 70–80% humidity; at 45% the body dries, they cannot breathe, and they leave the shell and weaken. The correct answer is to restore humidity and temperature quickly, place it on moist sand, and set several shells beside it so it can choose one itself. Forcing it into a shell injures the soft abdomen. Submerging it drowns it, and plastic wrap suffocates it. Out of the shell and motionless is an emergency; if the response is weak, consult a hospital the same day.

IssuesSwitching off the heating on a winter night and letting humidity fall to 45% was the direct cause. The owner looked at the hygrometer but did not understand why 70–80% must be maintained. There was no lid that holds heat and humidity and no automated environment.

ImprovementIn winter, maintain 20°C or above and 70% humidity or above around the clock with a humidity-retaining lid and panel heater, and check the hygrometer every morning. Keep a mister handy and mist morning and evening during the dry heating season. Always keep several boiled, sterilized spare shells in the tank.

A May evening. The 5 Amano shrimp sharing a 60 cm tank with tropical fish have not eaten algae or food for a week and stay hidden behind the driftwood. Water temperature 24°C. Because the plants were growing poorly, you started adding liquid fertilizer daily a week ago. The fish are swimming normally.

What should you check and do first?

1. Assume they are bored with the food; switch types and feed more
2. They are just hiding, so do nothing and observe
3. Check the ingredients of the new liquid fertilizer; if it contains copper, stop it and do small water changes for several days
4. Assume the fish are chasing them and remove all the fish

AnswerC. Check the ingredients of the new liquid fertilizer; if it contains copper, stop it and do small water changes for several days

ExplanationWhen shrimp suddenly stop eating and stay hidden, first suspect anything newly added just before. Some aquarium plant fertilizers contain copper or heavy metals that are harmless to fish but lethal to shrimp in trace amounts. The correct answer is to stop dosing, check the ingredients, and do small water changes of 1/4 or less for several days to lower the concentration. More food fouls the water, and leaving them weakens them to death. Removing all the fish misses the cause. If they become sluggish or turn cloudy white, seek advice the same day.

IssuesThe owner did not know that shrimp are extremely sensitive to copper and chemicals and dosed fertilizer daily without checking the ingredients. Because the fish were fine, the shrimp's change was dismissed as just hiding and left for a week.

ImprovementCheck the ingredient list of every medication, fertilizer and additive before it goes in the tank, and never use copper-containing products in a shrimp tank. Record the date anything new is added and make a habit of linking it to any change. Observe the response to food every day.

A July evening. Your land hermit crab, kept for two years, now bulges far out of its shell and can no longer withdraw into it. The only spare shells are the two small ones that came with it at purchase, both smaller than its current shell. It increasingly sits motionless on the climbing wood and drags its shell as it walks.

What is the most appropriate response?

1. Take it out of its current shell and put it into a somewhat larger shell by hand
2. Boil and sterilize several shells one size larger, place them nearby and wait for it to choose one and move in on its own
3. The shell is just heavy, so break off part of the current shell to lighten it
4. It can live without a shell, so remove it and observe

AnswerB. Boil and sterilize several shells one size larger, place them nearby and wait for it to choose one and move in on its own

ExplanationLand hermit crabs choose and change shells themselves as they grow. Bulging out of the shell leaves the soft abdomen prone to drying and injury, prevents molting, and is dangerous. The correct answer is to boil-sterilize several shells one size larger, line them up, and wait for it to move on its own. Taking it out of or putting it into a shell by hand injures the abdomen, and breaking the shell destroys its home. Without a shell it dries out and dies quickly. If it has not moved and stops moving after several days, consult a hospital.

IssuesThe owner failed to provide shells matching its growth and had only the small ones from purchase. They did not know the basic rule that spare shells must be several, all larger than the current one, and did not notice until it was bulging out.

ImprovementAlways keep 3–5 boiled, sterilized shells one size larger than the current one in the shell area. Check body size every six months and update shell sizes. Never use painted shells.

A September morning. The cherry shrimp in your 20 L tank have bred, and there are now over 50 including babies. The weekly test shows high nitrite for the first time. The shrimp still look normal, but leftover food and droppings have built up on the bottom. The only filtration is one small sponge filter.

What is the most appropriate action to take before the shrimp show symptoms?

1. No symptoms, so do nothing until next week's test
2. Do a complete water change and wash all the substrate to bring nitrite to zero
3. Change 1/4 of the water every few days with water at the same temperature, feed less and remove leftovers, and work on adding a filter and reducing crowding
4. Add a nitrite-removing chemical at double the recommended dose

AnswerC. Change 1/4 of the water every few days with water at the same temperature, feed less and remove leftovers, and work on adding a filter and reducing crowding

ExplanationRising nitrite means pollution from overcrowding and leftover food has exceeded filter capacity. Shrimp are more sensitive than fish, and by the time symptoms appear it is too late. The correct answer is to repeat small water changes every few days to lower the level, feed less, add filtration and reduce crowding. A complete water change and substrate washing loses the bacteria, abruptly changes the water and triggers molting failure. Double-dosing chemicals can harm shrimp depending on ingredients and does not solve the root cause. If shrimp start gathering at the surface, switch to immediate water changes.

IssuesDespite the population growing through breeding, the owner did not review filtration or feeding and exceeded filter capacity. By the guideline of 20 L for 10 shrimp this was clearly overcrowded, with no plan for managing numbers or rehoming.

ImprovementKeep testing weekly and increase water-change frequency when nitrite appears. Run two filters, and consider an additional tank or rehoming when baby shrimp multiply. Feed every other day, only as much as is finished, and remove leftovers each time.

A November evening. The water in a 30 cm tank with 20 cherry shrimp has suddenly turned cloudy white, and most of the shrimp, lively this morning, are now motionless on the bottom. A few are twitching their legs. Three days ago you washed the filter sponge thoroughly under tap water and replaced the filter media with new. The temperature is unchanged at 22°C.

What is the most likely cause, and what should you do now?

1. Filter cleaning destroyed the bacteria and the water quality crashed. Change 1/3 with water at the same temperature, increase aeration, stop feeding, and keep changing water while testing over the following days
2. White muscle disease has spread through the tank. Isolate all the shrimp and treat with fish medication
3. The water is just white, so wait until it clears
4. The new media is not working. Remove the filter and switch to natural filtration

AnswerA. Filter cleaning destroyed the bacteria and the water quality crashed. Change 1/3 with water at the same temperature, increase aeration, stop feeding, and keep changing water while testing over the following days

ExplanationWashing the sponge under tap water and replacing all the media wipes out the filter bacteria at once; ammonia and nitrite surge and the water turns cloudy. Shrimp lying still and twitching their legs is a poisoning sign and an emergency. The correct answer is a water change with dechlorinated water at the same temperature, strong aeration and no feeding, then continued small changes while testing over the following days. Fish medication kills shrimp. Ignoring the cloudiness can wipe out the tank overnight, and removing the filter makes it worse. If the number of motionless shrimp keeps rising, seek advice the same day.

IssuesThe owner did not understand that the filter houses the bacteria and that washing it under tap water or replacing everything stops filtration. They did not know that making things clean can harm the tank.

ImprovementRinse the sponge gently in tank water, and replace media a portion at a time every few weeks, never all at once. Do not clean the filter and change water on the same day. Test daily for a week after cleaning and keep water ready for changes.

An August evening. Of two land hermit crabs in a 45 cm tank, the one that just finished molting and emerged from the sand has had its shell taken by the other and is naked on the sand. Its body still looks soft, and the thief keeps trying on the new shell. No spare shells are in the tank.

What is the most appropriate first action?

1. Catch the thief, pull it out of the shell and return the shell to its owner
2. Isolate the naked crab in a separate container lined with moist sand and paper towel, keep humidity and temperature steady, and quickly add several suitable shells
3. It is nature's way, so leave the two together and do not intervene
4. Put the naked crab in the water dish to prevent drying

AnswerB. Isolate the naked crab in a separate container lined with moist sand and paper towel, keep humidity and temperature steady, and quickly add several suitable shells

ExplanationA freshly molted land hermit crab has a soft body and, without a shell, dies quickly from drying and attack by its tankmate. The correct answer is to isolate the naked crab in a separate container with moist sand or paper towel, maintain 70–80% humidity and around 25°C, and add several suitably sized shells for it to choose from. Pulling the thief out of the shell injures both. Left alone, the naked crab will be attacked; in the water dish it drowns. If it cannot get a shell and stops moving, seek advice the same day.

IssuesNo spare shells were provided, creating an environment where the two crabs fought over shells. The owner did not know hermit crabs are solitary and defenseless after molting, and had no plan to isolate the freshly molted animal.

ImprovementAlways keep several shells of various sizes that fit each crab. When one buries to molt, be ready to use a divider or isolation container to protect it from the tankmate. For multiple crabs, ensure ample space and hiding places, and separate into different tanks if fighting continues.

11 p.m. in June. In a 20 L tank with 20 cherry shrimp, one that had just molted was swarmed by the others. You hurriedly shooed them away by hand, but that shrimp is missing two legs and a little pale bluish fluid is seeping out. The only cover is a bit of moss; there are no tubes or driftwood.

What is the most appropriate response for this shrimp?

1. Apply human antiseptic to the wound with a cotton swab to prevent infection
2. Isolate it in a separate container of fresh tap water until the wound heals
3. Move it to a hiding place, keep the water clean and watch without touching. The legs regrow at the next molt
4. The bleeding will not stop, so press the wound with your finger to stop it

AnswerC. Move it to a hiding place, keep the water clean and watch without touching. The legs regrow at the next molt

ExplanationRight after molting the body is soft and tankmates may attack. A shrimp's pale bluish fluid stops on its own in clean water, and lost legs regrow over several molts. The correct answer is to move it to a hiding place, keep the water clean and not touch it. Antiseptic is lethal even in trace amounts, and tap water kills through chlorine. Pressing a tiny shrimp with a finger crushes it. Place food nearby, and if it remains motionless and not eating, seek advice the same day.

IssuesWith 20 shrimp and only a little moss for cover, the freshly molted animal had nowhere to escape. Not knowing about shrimp body fluid and regeneration, the owner thought of human-style bleeding control and disinfection.

ImprovementPlace ceramic tubes, driftwood and dense moss in numbers exceeding the shrimp to create layered hiding places. When you find a molted shell, leave the tank undisturbed for a few days. Remember the rule: bleeding and lost limbs are handled with water quality, not handling.

An April afternoon. While trying to scoop up your Japanese freshwater crab with a net for tank cleaning, you pulled on the claw tangled in the mesh and the larger claw came off cleanly at the base. The crab is raising its remaining claw in threat. A little fluid is coming from the stump, but not much.

What is the most appropriate follow-up?

1. Reattach the claw with instant glue
2. Do not handle it; keep it quiet, keep the water clean and place food nearby. The claw regrows over several molts
3. Worried about infection, give it a medicated bath with fish medication
4. Put it on land and keep it out of water for a day to dry the wound

AnswerB. Do not handle it; keep it quiet, keep the water clean and place food nearby. The claw regrows over several molts

ExplanationCrabs self-amputate legs or claws when grabbed in order to escape. The stump seals naturally and the claw regrows over several molts. The correct answer is to leave it alone, keep the water clean to prevent infection and place food nearby. Glue is toxic and fish medication is lethal to crabs. Drying damages the gills and weakens it. With one claw it struggles to eat until the next molt, so cut food small. If several legs are lost and it cannot eat, seek advice the same day.

IssuesThe owner caught it forcibly with a net and pulled on the tangled claw. They did not know crabs self-amputate and had not thought about how to move it for each cleaning. They also lacked the understanding that regrowth requires molting.

ImprovementMove it not with a net but by scooping it with water in a container or cup it walks into on its own. Never grab legs or claws. Minimize how often it is moved for cleaning, and postpone cleaning during molting periods. Keep the water clean and wait for regrowth.

Late at night in September, a loud noise comes from the tank. You find your land hermit crab, fallen from the top of driftwood stacked 40 cm high, lying on a hard stone near the glass. The shell is cracked and half its abdomen is visible. Its legs move but it does not walk. Two spare shells are in the tank.

What is the most appropriate first action?

1. Remove the cracked shell by hand and put its body into a spare shell
2. Place several spare shells nearby, keep it on moist sand, dark and quiet, and consult a hospital immediately if it does not move
3. Repair the cracked shell with tape and put it back where it was
4. Put it in the water dish to rest and ease the shock

AnswerB. Place several spare shells nearby, keep it on moist sand, dark and quiet, and consult a hospital immediately if it does not move

ExplanationA cracked shell with the body exposed is an emergency with high risk of drying and injury. The correct answer is to place several boiled, sterilized spare shells nearby so it can move in on its own, and keep it on moist sand, dark and quiet. Removing the shell and transferring it by hand injures the soft abdomen. Tape adhesive is harmful, and in the water dish it drowns. Body exposed and not moving is a call-now sign: phone a hospital that treats invertebrates.

IssuesThe driftwood was stacked above the 30 cm climbing-height guideline and a hard stone sat at the landing point. The layout ignored the nocturnal habit of climbing actively at night and was not designed with falls in mind.

ImprovementKeep climbing wood under 30 cm with only soft, moist sand below. Move stones and hard decorations to the edges. Always keep 3–5 shells, in the current size and one size larger, so it can move in immediately if its shell cracks.

A July morning. In a tank where cherry shrimp have bred, you spot several tiny baby shrimp swimming inside the hang-on-back filter. There was no sponge on the intake. Some inside the filter are moving, others are not. The water is 25°C and the adults are on the moss as usual.

What is the most appropriate first action?

1. Stop the filter, take it apart, gently scoop the babies out with tank water and return them to the tank, then fit a sponge on the intake
2. Reverse the filter flow to push the babies back into the tank
3. The babies will die anyway, so leave them and keep the filter running
4. Drain the filter water and pick out only the surviving babies

AnswerA. Stop the filter, take it apart, gently scoop the babies out with tank water and return them to the tank, then fit a sponge on the intake

ExplanationBaby shrimp are easily sucked into filters and get battered and injured inside. The correct answer is to stop the filter first, take it apart, gently rescue them together with the tank water and return them to the clean tank. Injuries heal at the next molt. At the same time, fit a sponge filter on the intake to prevent recurrence. Reversing the flow injures them further, and draining washes them away to die. Left alone, they all die and rot inside the filter, fouling the water.

IssuesThe owner did not anticipate breeding and left the intake unprotected. They did not know babies are especially easily drawn in, and the filter choice (a sponge filter is recommended) was inappropriate.

ImprovementAlways fit a sponge or strainer cover on the intake. Use a sponge filter for breeding tanks. Look inside the filter daily to check for baby shrimp, and check for them when cleaning too.

A May evening. The three Japanese freshwater crabs in your 30 cm tank fought fiercely; the edge of the smallest one's carapace is cracked and seeping pale bluish fluid, and it lost a leg. It sits motionless in a corner. The land area is small, the only hiding place is a single stone, and the two larger crabs are still fighting over it. Water temperature 21°C.

What is the most appropriate follow-up?

1. Isolate the injured crab in a separate container with a hiding place, keep the water clean and watch without handling. In future keep crabs singly or in a large tank
2. Cover the crack with a waterproof bandage and return it to the tank
3. To stop the fighting, calm all three together in a small container
4. Put it on a dry part of the land area and keep it out of water so the wound dries and heals

AnswerA. Isolate the injured crab in a separate container with a hiding place, keep the water clean and watch without handling. In future keep crabs singly or in a large tank

ExplanationFreshwater crabs are strongly territorial, and keeping several in a small tank leads to cannibalism. The pale bluish fluid stops on its own in clean water, and the leg regrows with molting. The correct answer is to isolate the injured crab in a separate container with cover and let it recover in clean water. Bandage adhesive is harmful, and crowding them into a small container intensifies fighting. Drying damages the gills and weakens it. If it does not eat or move for several days or the crack spreads, seek advice the same day.

IssuesThree crabs were housed together, exceeding the guideline of 1–2 per 30 cm tank, with only one hiding place. The owner underestimated crabs' territoriality and cannibalism and missed the signs of fighting.

ImprovementKeep freshwater crabs singly as a rule; if several, use a large container with more hiding places than crabs. Make the layout half land and half shallow water, and keep a spare container to isolate molting animals immediately. Separate them at the first sign of fighting (lost legs).

A Sunday afternoon. A school-age child was holding a Japanese freshwater crab in their hand when it clamped hard onto their index finger with its large claw. The child is crying and about to flail their hand. The crab will not let go; the fingertip is red and a little blood is showing.

What is the most appropriate first action?

1. Hold the crab's body and pry it off the finger
2. Shake the hand to fling it off
3. Put the hand, crab and all, into the tank water and hold still until the crab lets go on its own
4. Pour hot water on the crab to startle it

AnswerC. Put the hand, crab and all, into the tank water and hold still until the crab lets go on its own

ExplanationThe more a crab is pulled, the harder it pinches. Forcing it off makes the claw self-amputate and tears the finger further. The correct answer is to put the pinched hand into water and wait without moving. In water the crab calms down and lets go. If it does not, gently support the rear of its body to prompt movement. Shaking it off injures the crab in the fall, and hot water is lethal and still does not make it release. Afterward, wash the wound under running water, disinfect, and see a doctor if it swells or festers.

IssuesThe child was allowed to hold and play with the crab bare-handed. The family did not understand that crabs are timid and pinch defensively when grabbed, and had not shared what to do when pinched.

ImprovementFreshwater crabs are for observing, not for handling or play. When handling is necessary, an adult holds the back of the carapace. Teach everyone in the family: if pinched, put it in water and wait. Always wash hands after touching.

A March morning. Your land hermit crab is hanging in midair with a leg caught between the sliding lid and the glass rim. Last night you had just narrowed the gap to prevent escapes. The leg is bent and pinched, and the crab is struggling to withdraw into its shell. You do not know how long it has been stuck.

What is the most appropriate first action?

1. Hold the shell and pull downward to free the leg
2. Slowly open the lid to widen the gap, wait for it to free itself, then place it on moist sand and keep quiet
3. Cut off the trapped leg at the base with scissors to free it
4. Leave it and wait for it to work itself free

AnswerB. Slowly open the lid to widen the gap, wait for it to free itself, then place it on moist sand and keep quiet

ExplanationPulling on a trapped leg causes self-amputation or joint damage. The correct answer is to move the lid to widen the gap itself and let the crab pull its leg out on its own. Once free, place it on moist sand in the dark and quiet. Even if the leg is lost, it regrows with molting. Pulling the shell or cutting the leg causes needless damage. Leaving it leads to drying and exhaustion. If it stays motionless and does not emerge from its shell after release, seek advice the same day.

IssuesNarrowing the lid gap to prevent escape left a gap just wide enough for a leg, which actually created a trapping hazard. The owner did not account for the hermit crab's habit of climbing the walls and hooking its legs on the lid.

ImprovementMake the lid gap-free, or switch to a mesh or sealed type that legs cannot enter. After installing, check how it moves when climbing at night. Inspect decorations and cords for trapping gaps too, and observe nighttime climbing behavior.

Saturday noon. A preschool child, wanting to see it, scooped an Amano shrimp out of the tank by hand and dropped it from their palm onto the floor. The shrimp flipped on the floor; when picked up, one leg is bent and it stays curled up, moving weakly. The tank is 23°C and the floor is hard wood flooring.

What is the most appropriate response for the shrimp?

1. Straighten the bent leg before returning it to the tank
2. Return it to the tank at once, keep it quiet near a hiding place and watch without touching. The bent leg will be fixed by molting
3. Put it in a cup of tap water and wait for it to recover
4. It is weak, so do not return it to the tank; wrap it in wet tissue and keep it warm

AnswerB. Return it to the tank at once, keep it quiet near a hiding place and watch without touching. The bent leg will be fixed by molting

ExplanationA shrimp kept in air for long has its gills dry out and cannot breathe. The correct answer is to return it to its tank immediately and leave it undisturbed near a hiding place. The bent leg returns to normal at the next molt. Straightening the leg by hand breaks it and causes self-amputation. Tap water is lethal through chlorine; wrapped in tissue it cannot breathe, and warming is unnecessary and counterproductive. If its swimmerets move after return and it eats the next day, it has recovered. If it stops moving, seek advice the same day.

IssuesA child could reach into the tank, and nobody had explained the dangers of taking a shrimp out of water (drying, falls, self-amputation). The lid and supervision were inadequate.

ImprovementPlace the tank where children cannot reach in, or use a heavy lid, and make it a rule to observe through the glass. If a shrimp must be moved, scoop it with water in a cup. Share with the family that shrimp are not to be touched, and that if one is dropped, it goes straight back into water.

A February evening. You keep 6 Amano shrimp with angelfish in a 60 cm tank. One shrimp that had just molted was chased and pecked by the fish, suffering an abdominal wound and losing half an antenna. It has fled under the driftwood, but the fish keep circling.

What is the most appropriate first action?

1. Scoop the injured shrimp with tank water in a cup, isolate it in a separate container with a hiding place and keep it quiet
2. Feed the fish extra to distract them from the shrimp
3. Apply fish medication to the shrimp's wound and return it to the tank
4. It is natural, so do not intervene and check in the morning

AnswerA. Scoop the injured shrimp with tank water in a cup, isolate it in a separate container with a hiding place and keep it quiet

ExplanationA freshly molted shrimp is an easy meal for fish. The correct answer is to scoop the injured animal out with water, isolate it in a separate container with cover, and let it recover in clean water. The wound and antenna regenerate with molting. Extra food does not stop predation and fouls the water. Fish medication is lethal to shrimp. Left until morning it will very likely be eaten. Going forward, add more hiding places or reconsider the mixed tank altogether.

IssuesThe owner did not recognize that keeping shrimp with medium to large fish carries a high risk of freshly molted shrimp and babies being eaten. Apart from the driftwood there was little dense cover, so molting shrimp could not escape.

ImprovementLimit tankmates to small, peaceful fish and build layered hiding places with moss and driftwood that fish cannot enter. Keep a dedicated isolation container for shrimp, and watch especially closely for a few days after finding a molted shell. If shrimp keep disappearing, stop keeping them with fish.

An October morning. One of the cherry shrimp in your 20 L tank is stuck with its body wedged in a narrow split in the driftwood and cannot move. It is working its legs trying to get out but cannot. Other shrimp are gathering around. It seems to have been struggling bit by bit since yesterday.

What is the most appropriate response?

1. Grip the shrimp's body with tweezers and pull it out
2. Gently lift the driftwood under water and widen the gap or tilt the split side slightly so it can get out on its own, then move it to a hiding place
3. Wait for the shrimp to molt and become slimmer on its own
4. Take the driftwood out of the tank to dry so the gap opens, then put it back

AnswerB. Gently lift the driftwood under water and widen the gap or tilt the split side slightly so it can get out on its own, then move it to a hiding place

ExplanationPulling a wedged shrimp by the body cracks the shell or makes legs self-amputate. The correct answer is to gently move the driftwood under water to widen the gap so the shrimp can free itself, then move it to a hiding place. Injuries heal with molting. Waiting for a molt leads to exhaustion and attack by tankmates. Taking the driftwood out of the tank to dry leaves the shrimp unable to breathe. If it stays motionless and does not eat the next day after freeing, seek advice.

IssuesDriftwood with a narrow split a shrimp could enter was placed as is. The owner did not know the basic rule of avoiding narrow gaps, and was slow to notice although something had been wrong since the day before.

ImprovementCheck driftwood and stones for gaps; fill narrow splits with moss or widen them with a file. During daily observation, check for any animal that has not moved from the same spot. Always carry out rescues under water and never grip the body.

An August morning. The tank lid was slightly askew and the Japanese freshwater crab is gone. You find it in a corner of the hallway, covered in dust and not moving. It apparently escaped overnight; its body is dry and its legs stiff, but they twitch slightly when touched. The air conditioning is off and the room is nearly 30°C.

What is the most appropriate first action?

1. Wrap it in a wet cloth to moisten it, return it to clean shallow water at the same temperature, keep it dark and quiet in a hiding place and watch for several hours
2. Submerge it straight into cold tap water to rehydrate it at once
3. It is not moving, so conclude it is dead and bury it
4. Blow off the dust with the cool setting of a hair dryer, then return it

AnswerA. Wrap it in a wet cloth to moisten it, return it to clean shallow water at the same temperature, keep it dark and quiet in a hiding place and watch for several hours

ExplanationA freshwater crab can breathe on land as long as its gills are moist, but it weakens rapidly from drying and heat. If the legs move even slightly, it is alive. The correct answer is to wrap it in a wet cloth to moisten it, return it to shallow dechlorinated water at the same temperature, and watch in the dark and quiet. Cold chlorinated water adds temperature shock and chlorine on top. Do not assume death if the legs respond, even if it is not moving. Cool air dries it further. If there is no response after several hours, seek advice.

IssuesLid gap control was lax, and the owner underestimated crabs' habit of climbing walls to escape. They did not account for nocturnal activity, and let the room approach 30°C in summer.

ImprovementUse a gap-free lid with a weight on it, and seal cable holes too. Make a habit of counting animals every morning. Keep a wet cloth and stored water ready in case of escape, and keep room and water temperature at 25°C or below in summer.

A December evening. Your land hermit crab escaped through the cable gap in the tank lid. The living room is heated but the humidity is 40%, and after 30 minutes of searching you cannot find it. Under the sofa and in the gaps between furniture it is too dark to see. A family member is about to start vacuuming.

What is the most appropriate action?

1. Vacuum while moving the furniture to search everything at once
2. Wait for it to come back on its own and search again tomorrow morning
3. Stop the vacuuming and foot traffic and search dark, damp places with a flashlight. Put a damp cloth or water dish in the room corners; when found, wrap it in a wet cloth and return it
4. Mist the whole room to raise the humidity before searching

AnswerC. Stop the vacuuming and foot traffic and search dark, damp places with a flashlight. Put a damp cloth or water dish in the room corners; when found, wrap it in a wet cloth and return it

ExplanationIn a room at 40% humidity a land hermit crab dries out within hours, and it also risks being stepped on. The correct answer is first to stop vacuuming and walking to prevent a trampling accident, then search dark, damp places (under furniture, around houseplant pots, the bathroom) with a flashlight. A damp cloth or water dish attracts it. When found, wrap it in a wet cloth to moisten it and return it. Waiting until morning carries a high risk of desiccation death or trampling. Misting does not improve whole-house humidity and wastes time.

IssuesThe cable gap was not sealed, and the owner did not know hermit crabs climb cords. They also did not realize that a room dried out by winter heating is fatal to an escapee.

ImprovementRoute cables outside the lid, or seal the gap completely with sponge or tape. Check the lid before the active nighttime hours. Share the escape procedure (stop vacuuming, damp cloth) with the family, and site the tank in a room with little furniture.

A May evening, right after swapping in a powerful filter, you find several cherry shrimp have jumped out of the lidless tank and are flipping on the floor. One is no longer moving; two are still flipping. The tank is 24°C. The floor is carpet and fibers are stuck to their bodies.

What is the most appropriate first action?

1. Remove the fibers thoroughly before returning them to the tank
2. Return the flipping ones to the tank immediately, return the motionless one too and check for swimmeret movement. Then reduce the filter flow and fit a lid
3. Throw the motionless one in the trash and return only the flipping ones
4. Put them all in a cup of tap water and observe

AnswerB. Return the flipping ones to the tank immediately, return the motionless one too and check for swimmeret movement. Then reduce the filter flow and fit a lid

ExplanationOnce its gills dry in air, a shrimp has trouble breathing within minutes. The correct answer is to get the live ones back into the tank as fast as possible, return the motionless one as well, and check for life by swimmeret movement. Fibers come off naturally in water. Shrimp that look motionless sometimes recover when returned to water. Tap water is lethal because of chlorine. After returning them, reduce the strong current that caused the jump and seal the gaps with a lid.

IssuesShrimp flick backward when startled and can jump out of the tank, yet the owner switched to a strong-flow filter with no lid. There was no preparation for jump-outs (lid, flow adjustment).

ImprovementAlways keep a lid on a shrimp tank, and set the filter flow low or use a sponge filter. Observe for several hours on any day equipment is changed. Make it a rule that a shrimp on the floor goes straight back into water, and count the shrimp daily.

A Sunday morning. For tank cleaning you moved your Japanese freshwater crab to a bucket on the floor, but did not notice it had climbed out, and stepped on it at your feet. Part of the carapace is dented, two legs have come off and fluid is leaking. It is moving, but weakly.

What is the most appropriate first action?

1. Press the dented carapace back into shape with your finger
2. Place it on dry paper to rest so the wound dries
3. Crush a human painkiller and dissolve it in the water to ease the pain
4. Return it gently to clean, shallow water at the same temperature, keep it dark in a hiding place, watch for several hours without touching, and seek advice immediately if it stops moving

AnswerD. Return it gently to clean, shallow water at the same temperature, keep it dark in a hiding place, watch for several hours without touching, and seek advice immediately if it stops moving

ExplanationExoskeleton damage from being stepped on cannot be repaired by a person. The correct answer is to return it to clean shallow water at the same temperature and watch it, untouched, in a dark hiding place. The fluid loss stops on its own in clean water and the legs regrow with molting, but whether it survives the carapace damage depends on holding out until the next molt. Pressing the carapace injures the organs, and on dry paper the gills dry out. Human medication ruins the water and is lethal. If the legs stop responding or it still will not eat the next day, seek advice.

IssuesThe holding container used during cleaning had no lid, and the owner forgot that crabs climb walls and get out. They neglected the basic rule of watching where they step, and managed the holding container carelessly.

ImprovementAlways use a lidded holding container during cleaning, placed on a table rather than the floor. Confirm where the animal is before starting and watch your feet while working. Set a cleaning routine that minimizes how long the animal is out of its tank.

A noon in April. You find your cat with its front paw in the lidless cherry shrimp tank, stirring it up. The water is cloudy, torn moss is floating, and the shrimp are huddled in a corner. Several have been flung onto the floor, and the cat is about to take one in its mouth. The tank is 23°C and the floor is dry wood flooring.

What is the most appropriate first action?

1. Move the cat away, return the floor shrimp to the tank at once, do a small water change at the same temperature if the water is very cloudy, and fit a heavy lid
2. Scold the cat; the floor shrimp are probably dead, so clean them up
3. Do a complete water change right away to sanitize the water the cat touched
4. Put the tank back in order and let the cat continue to roam freely

AnswerA. Move the cat away, return the floor shrimp to the tank at once, do a small water change at the same temperature if the water is very cloudy, and fit a heavy lid

ExplanationShrimp cannot breathe in air after a few minutes. The correct answer is to move the cat away first and return the floor shrimp to the tank immediately. Even if they are not flicking, check for life by swimmeret movement. If the water is very cloudy from debris stirred up by the cat's paw, do a small water change at the same temperature. A complete change loses the bacteria and abruptly changes the water. The cat will try again, so fit a heavy lid and reconsider the tank's location. A shrimp that was in the cat's mouth poses no lung fluke risk, but never let a cat eat raw freshwater crab.

IssuesThe owner kept a lidless tank in a home with a cat, neglecting the basic rule of a heavy lid to keep cats and birds out. They did not know the first response to shrimp on the floor and had not anticipated the cat's behavior.

ImprovementFit a heavy, gap-free lid and place the tank where the cat cannot climb onto it. Use a room the cat cannot enter, or put a barrier around the tank. Share with the family that a shrimp on the floor goes straight back into water, and check the lid daily.

July. You were keeping 30 cherry shrimp in a water-lily bowl on the balcony, but in two weeks they have dropped to about 10. There are several 3 cm dragonfly larvae in the bowl and water striders on the rim. This morning a heron-like bird was perched on the balcony railing. The water reaches nearly 30°C at midday.

What is the most appropriate response?

1. Spray insecticide around the bowl to stop dragonflies laying eggs
2. Shrimp breed naturally, so do nothing and keep observing
3. Net out all the shrimp and larvae and move only the shrimp to an indoor tank
4. Remove dragonfly larvae whenever found, cover the bowl with fine mesh, and shade it with a reed screen to lower the temperature

AnswerD. Remove dragonfly larvae whenever found, cover the bowl with fine mesh, and shade it with a reed screen to lower the temperature

ExplanationIn outdoor containers, dragonfly larvae, water striders and herons prey on shrimp. The correct answer is to remove larvae as soon as they are found, cover with fine mesh to block egg-laying dragonflies and visiting birds, and shade to limit temperature rise. Insecticide is the worst choice; even a trace wipes out the shrimp. Left alone, predation and heat will kill them all. Moving them indoors is an option in itself, but netting everything out causes limb loss and molting failure, and the water-chemistry difference causes shock. If moving them, acclimate them to the new water.

IssuesThe owner did not know the predator risks of outdoor keeping (dragonfly larvae, water striders, herons) and had no mesh or shade. They left the declining numbers for two weeks and did nothing about summer outdoor water reaching 30°C.

ImprovementFit mesh and shade on outdoor containers from the start, and check water temperature and numbers every morning. Check the bottom monthly for dragonfly larvae. Never use insecticides or mosquito repellents near the container. Keep a spare indoor tank to move them into on extreme-heat days.

A February evening. While digging with a scoop to replace the sand, you unearthed your land hermit crab in the middle of molting. The old exoskeleton is half off, its body is pure white and soft, and it is limp. Spare sand and shells are ready.

What is the most appropriate first action?

1. Peel off the remaining old exoskeleton by hand to complete the molt
2. Do not touch it; place it on moist sand, raise the humidity with a mister and keep dark and quiet. If possible, lightly cover it with moist sand, and do not touch it at all until tomorrow
3. Soak it in the seawater dish to prevent drying
4. Put it back on the sand with its tankmate and let nature take its course

AnswerB. Do not touch it; place it on moist sand, raise the humidity with a mister and keep dark and quiet. If possible, lightly cover it with moist sand, and do not touch it at all until tomorrow

ExplanationA land hermit crab mid-molt is extremely vulnerable, and being dug up is one of the most dangerous accidents. The correct answer is to touch it no further, place it on moist sand, raise the humidity as high as possible, and keep it dark and quiet until the next day. If possible, lightly cover it with moist sand to maintain darkness and humidity. Removing the exoskeleton kills it. Soaking in seawater drowns it, and the tankmate will attack the soft body. If it does not move and the molt does not progress for more than a day, that meets the call-now sign, so contact a hospital.

IssuesThe owner dug the sand without checking for a buried hermit crab. They did not follow the basic rules that sand is replaced partially and only when no animal is buried, and that you never dig during a molt.

ImprovementReplace sand partially once a month, only after confirming where every animal is. Do not dig while any animal is buried, and record the date it went under. Watch for mounds and entry holes in the sand to get an idea of where it is buried.

A Saturday evening you moved 15 cherry shrimp into a small lidless bucket to wash the tank, forgot about them, and noticed the next morning. The bucket had no aeration or hiding places, and the water is 18°C, 4°C colder than the tank. Several shrimp are gathering at the surface and two are motionless on the bottom.

What is the most appropriate action?

1. Hurry and return them all to the 22°C tank
2. Put a heater in the bucket and bring it to 22°C at once
3. Add aeration to the bucket and gradually add tank water over an hour to match temperature and water quality before returning them
4. Return only the ones at the surface first and discard the motionless ones

AnswerC. Add aeration to the bucket and gradually add tank water over an hour to match temperature and water quality before returning them

ExplanationA night in a small bucket brings low oxygen and fouling water, and gathering at the surface is the symptom. The correct answer is first to supply oxygen with aeration, then add tank water little by little to match temperature and water quality gradually before returning them. Returning them abruptly across a 4°C difference triggers molting failure. Rapid heating with a heater is another sudden change. Check the motionless ones in tank water for swimmeret movement too, and return them if they respond. If more shrimp stop moving after return, seek advice the same day.

IssuesThe holding container had no hiding places or aeration, and the time needed was underestimated. On top of the lapse of forgetting an interrupted task, the owner did not understand the importance of matching temperature when returning them.

ImprovementUse tank water in the cleaning holding container and add a lid, aeration and moss. Plan to finish within an hour and set a timer. Always check the temperature before returning them and acclimate gradually, for example by the drip method.

8 p.m. in March. You rinsed plants bought at a home center and planted them straight into a 20 L tank. Thirty minutes later all 15 cherry shrimp began swimming frantically and some started flipping over. The temperature is unchanged. The plant label did not say pesticide-free.

What is the most appropriate first action?

1. Remove all the plants, do two 50% water changes with dechlorinated water at the same temperature, add activated carbon and increase aeration
2. Move only the shrimp to a separate container of tap water and leave the plants in place
3. Add table salt to the tank as an antidote
4. Observe, and change the water if they are still suffering in the morning

AnswerA. Remove all the plants, do two 50% water changes with dechlorinated water at the same temperature, add activated carbon and increase aeration

ExplanationPesticide residue on plants is lethal to shrimp in trace amounts, and frantic swimming and flipping right after introduction are classic poisoning signs. The correct answer is to remove the offending plants immediately, do two 50% changes with dechlorinated water at the same temperature to lower the concentration, adsorb the chemical with activated carbon and secure oxygen with aeration. Tap water finishes them off with chlorine, and leaving the plants recontaminates. Salt is no antidote. Waiting until morning means losing them all. Several animals in distress at once meets the call-now sign.

IssuesThe owner did not know that pesticide residue on plants is lethal to shrimp and added plants without a pesticide-free label after only a rinse. They did not know about pretreating by soaking in a separate container for several days.

ImprovementChoose plants labeled pesticide-free, and even then soak them in a separate container for several days, changing the water daily, before adding. Watch the shrimp for an hour after introduction. Keep dechlorinated water and activated carbon on hand for emergency changes.

A January evening. Because the tropical fish in your 60 cm tank developed ich, you added a store-bought treatment at the recommended dose. Ten minutes later the 8 Amano shrimp sharing the tank are swimming wildly and bumping into the glass. One has begun turning cloudy white. The medication label says it contains copper.

What is the most appropriate first action to save the shrimp?

1. Add only activated carbon to weaken the medication and leave the shrimp in the tank
2. Evacuate the living shrimp immediately to a separate container of clean dechlorinated water (not tank water) with aeration and a hiding place
3. Change 1/4 of the tank water to dilute the medication
4. Shrimp get used to medication, so wait and see until tomorrow

AnswerB. Evacuate the living shrimp immediately to a separate container of clean dechlorinated water (not tank water) with aeration and a hiding place

ExplanationCopper-containing fish medications are lethal to shrimp, and frantic swimming followed by whitening is classic copper poisoning. Diluting the medicated tank is too slow to help. The correct answer is to evacuate the survivors immediately to clean, medication-free, dechlorinated water at the same temperature, with aeration and a hiding place, kept dark and quiet. Using tank water carries the medication with them. Activated carbon or a 1/4 change lowers the concentration too slowly, and shrimp do not adapt. If many are still suffering after evacuation, seek advice now. The original tank cannot take shrimp back until, after the treatment, a full water change is done and the media and substrate are washed.

IssuesThe owner did not know the basic fact that fish medications and copper are lethal to shrimp in trace amounts, and dosed the mixed tank directly. They ignored the rule of treating fish in a separate quarantine tank and failed to read the label.

ImprovementAlways give fish medicated baths in a separate container and never add medication to the main tank. Check the ingredients of any medication (copper, malachite green, etc.) beforehand. Keep an emergency container, dechlorinated water and aeration on hand, and wash equipment after any treatment.

A July night. You burned a mosquito coil in the room with the shrimp tank, closed the windows and went to bed. The next morning, half of the 20 cherry shrimp are motionless on the bottom and the rest are gathered at the surface twitching their legs. The lid is mesh, so smoke gets in easily. The water is 26°C and the water test shows nothing abnormal.

What is the most appropriate first action?

1. The water tests normal, so treat it as unexplained and observe
2. The water is warm, so lower it with a cooling fan
3. Fill the tank with diluted water to wash the shrimp's bodies
4. Ventilate and remove the mosquito coil, evacuate survivors to clean water at the same temperature, and clear the chemical from the tank with water changes and activated carbon

AnswerD. Ventilate and remove the mosquito coil, evacuate survivors to clean water at the same temperature, and clear the chemical from the tank with water changes and activated carbon

ExplanationThe ingredients of mosquito coils and insecticides (pyrethroids) dissolve from the air into the water surface and are lethal to shrimp in trace amounts. Water test kits cannot detect them. The correct answer is to ventilate and remove the source, evacuate survivors to clean water at the same temperature, and remove the chemical from the tank with water changes and activated carbon. Watching and waiting because the water tests normal means losing the rest. Temperature is not the cause, and washing the bodies is pointless. Several animals in distress at once meets the call-now sign.

IssuesThe owner did not know the basic rule not to keep the tank in a room where insecticides, mosquito coils or air fresheners are used. It never occurred to them that airborne chemicals dissolve into water, and the mesh lid left the tank unprotected.

ImprovementNever use mosquito coils, insecticide sprays, foggers or air fresheners in the room with the tank. Inform the whole family and rely on screens and physical mosquito control. When using a fogger in another room, seal the tank or stop the filter.

A November evening, a week after adding colored decorative shells and a small painted ornament from a discount store to the tank. You saw your land hermit crab scraping off and eating the ornament's paint. A large area of paint is gone, and today it is not eating and is sluggish. The water dish is tinted as if paint has leached into it.

What is the most appropriate first action?

1. Open the hermit crab's mouth and remove the paint
2. It is only sluggish, so observe and decide next week
3. Remove all painted items, wash the water dish and refill with fresh water, replace the contaminated sand, and consult a hospital today
4. Soak its whole body in salt water to detoxify

AnswerC. Remove all painted items, wash the water dish and refill with fresh water, replace the contaminated sand, and consult a hospital today

ExplanationPaints and adhesives contain solvents and heavy metals harmful to hermit crabs, and chewing them causes poisoning. The correct answer is first to remove all painted items, replace the contaminated water dish and sand to stop continued ingestion, and, because loss of appetite and sluggishness are already present, consult a hospital the same day. Trying to remove paint from its mouth is impossible and causes injury. Waiting until next week is likely to be too late. Soaking in salt water does not detoxify, and a land hermit crab will drown.

IssuesThe owner did not know hermit crabs chew on decorations and added painted items without caution. They lacked the principle that decorations must be unpainted and the basic rule of choosing unpainted shells.

ImprovementLimit tank decorations to unpainted driftwood, natural stone and boiled natural shells. Before adding anything new, check for paint, adhesive or preservatives. Watch daily for ingestion of foreign objects, and when appetite drops, immediately suspect the most recently added item.

A winter morning. To match temperature, you drew warm water from the water heater, added dechlorinator, and changed 1/3 of the Amano shrimp tank. Hours later, the 10 shrimp swam frantically, then turned cloudy white and died one after another; only two survive. The goldfish tank that received the same water is fine. The house is old and the hot-water pipes are copper.

What is the most likely cause, and what should you do for the survivors?

1. Copper poisoning from copper leached out of the pipes. Evacuate survivors to separate clean water (stored tap water brought to room temperature), then do a full change of the tank and wash the media and substrate
2. Not enough dechlorinator. Add double the dose to protect the rest
3. The warm water was too hot. Add cold water to lower the temperature
4. An unknown disease. Give the survivors fish medication

AnswerA. Copper poisoning from copper leached out of the pipes. Evacuate survivors to separate clean water (stored tap water brought to room temperature), then do a full change of the tank and wash the media and substrate

ExplanationWhen hot-water pipes are copper, copper leaches into the hot water. Fish can tolerate it, but to shrimp it is lethal in trace amounts, and frantic swimming, whitening and mass death are classic copper poisoning. The correct answer is to evacuate survivors to clean copper-free water (stored cold tap water brought to room temperature), then do a full change of the tank and wash the media and substrate to remove the copper. More dechlorinator or temperature adjustment misses the cause. Fish medication would add even more copper. Never use water from the water heater again.

IssuesThe owner used water-heater water to match temperature and did not know that water from copper pipes is lethal to shrimp. Because the goldfish were fine, the shrimp's extreme sensitivity to copper was easy to overlook.

ImprovementDraw cold tap water the day before and let it reach room temperature. Never use water-heater water or water that has passed through copper pipes. Consider a copper-removing adsorbent or filter for shrimp, and always observe for several hours after a water change.

2 p.m. in August. You come home to find the 30 cm tank in the closed-up room at 31°C. The 15 cherry shrimp are gathered near the surface and sluggish; a few are about to flip over. There is air conditioning but no cooling fan.

What is the most appropriate first action?

1. Put ice directly in the tank to drop it to 24°C at once
2. Change half the water with chilled water from the refrigerator to cool it immediately
3. Turn on the air conditioning, float a frozen water bottle to lower the temperature 1°C per hour, add aeration and stop feeding
4. Take the shrimp out and let them rest in the refrigerator's vegetable drawer

AnswerC. Turn on the air conditioning, float a frozen water bottle to lower the temperature 1°C per hour, add aeration and stop feeding

ExplanationShrimp are in danger above 28°C, and above 30°C is the lethal range. Gathering at the surface signals low oxygen and exhaustion from heat. The correct answer is to lower the room temperature with air conditioning, float a frozen water bottle to cool gradually at 1°C per hour, add oxygen with aeration, and stop feeding to prevent fouling. Dropping the temperature abruptly with ice or chilled water causes molting failure or shock. Putting them in the refrigerator is far too great a temperature difference, plus drying, and is fatal. If the number of motionless shrimp keeps rising, seek advice now.

IssuesThe owner kept the tank in a closed-up summer room with no cooling equipment and did not anticipate the temperature rising while out. They were only vaguely aware that shrimp need 25°C or below and had no cooling fan or similar prepared.

ImprovementInstall a cooling fan or chiller by June, and when out, manage room temperature with the air conditioner on low or on a timer. Always keep frozen water bottles in the freezer. Fit a max-min thermometer to check the water temperature while away.

10 p.m. in January. Snow has caused a power outage, and the panel heater and humidity equipment for the land hermit crab tank have stopped. The room has already dropped to 12°C, and the two hermit crabs are barely moving on the sand. There is no estimate for restoration. In the house you have disposable hand warmers, blankets and a styrofoam box.

What is the most appropriate response?

1. Put the hermit crabs in your clothing pocket to warm them with body heat
2. Cover the tank with the styrofoam box or blankets, attach hand warmers wrapped in cloth to the outside of the tank walls to hold around 20°C, and maintain humidity with a mister
3. Put the tank right in front of the stove to heat it quickly
4. Place the hermit crabs directly on a hot-water bottle to warm them

AnswerB. Cover the tank with the styrofoam box or blankets, attach hand warmers wrapped in cloth to the outside of the tank walls to hold around 20°C, and maintain humidity with a mister

ExplanationLand hermit crabs stop being active below 20°C and are at risk of death below 10°C. The correct answer is to cover the tank with insulation or blankets to keep heat in, attach cloth-wrapped hand warmers to the outside of the walls for gentle warmth, and keep humidity at 70% or above with a mister. Hand warmers get locally very hot on direct contact and consume oxygen, so never put them inside the tank. A pocket is dry and compresses them. In front of a stove or directly on a hot-water bottle is dangerous due to sudden temperature difference and drying. If they are still motionless and below 10°C in the morning, seek advice now.

IssuesThere was no preparation for keeping warm during a winter outage, and no heat source other than the heater had been considered. Measures should have begun before the room fell to 12°C, but the owner did not understand how fast the temperature would drop.

ImprovementKeep a styrofoam box, blankets, hand warmers and a mister as an emergency kit near the tank. Consider a USB heater or warming products that run on a power bank. Write out the outage procedure, post it, and share it with the family.

2 a.m. A strong earthquake shook the 20 L tank on a shelf, spilling half the water and collapsing the moss and driftwood. The 10 cherry shrimp are in the remaining water, but the filter is running dry because of the low water level and the water is cloudy. No shrimp are on the floor. Aftershocks continue.

What is the most appropriate first action?

1. Top up with plain tap water to restore the water level
2. Afraid of aftershocks, leave the tank as it is until morning
3. Take all the shrimp out and move them to a separate container of fresh water
4. Stop the dry-running filter, slowly top up with stored or dechlorinated water at the same temperature, and move the tank to a low, stable place

AnswerD. Stop the dry-running filter, slowly top up with stored or dechlorinated water at the same temperature, and move the tank to a low, stable place

ExplanationA filter running dry from a low water level overheats and fails, and filtration stops. The correct answer is to stop the filter first, add dechlorinated water at the same temperature little by little to avoid a sudden change, and move the tank to a low, stable spot. Plain tap water kills through chlorine. Leaving it lets low oxygen and fouling progress. Moving them all to fresh water causes shock from the water-chemistry difference. The next day, test the water and restore the collapsed hiding places.

IssuesThe tank was placed on a high shelf with no earthquake measures, and no stored water was ready. The owner had not thought about tank placement, earthquake securing, or the first response in a disaster (stop filter, top up water).

ImprovementPlace the tank on a low, stable stand and secure it with anti-slip mats and a lid. Always keep several liters of dechlorinated water stored, and have a battery-powered air pump for emergencies. Decide the disaster procedure in advance (stop filter, top up, relocate).

A September evening. An evacuation order has been issued as a typhoon approaches. You want to bring the Japanese freshwater crab you keep in a 30 cm tank, but the shelter is 20 minutes by car and a power outage is possible. On hand you have a small lidded plastic case, tank water, ice packs and paper towels. The air temperature is 28°C.

What is the most appropriate way to carry it?

1. Load the whole tank into the car, filled to the brim with water
2. Put a shallow layer of tank water in the plastic case with a stone for cover or wet paper towel, keep it dark, and wrap an ice pack in cloth against the outside while carrying
3. Carry it in a plastic bag without water
4. Leave it behind with extra food in the tank

AnswerB. Put a shallow layer of tank water in the plastic case with a stone for cover or wet paper towel, keep it dark, and wrap an ice pack in cloth against the outside while carrying

ExplanationA freshwater crab can breathe on land as long as its gills are moist, and shallow water with cover is safer than deep water. The correct answer is a lidded plastic case with shallow tank water, cover or wet paper towel to keep it moist, carried in the dark. At 28°C it is warm, so place a cloth-wrapped ice pack on the outside, adjusting to avoid overcooling. Carrying a full tank is heavy and dangerous as water sloshes out. A bag without water dries it out, and extra food left behind fouls the water and kills it. At the shelter, change the water daily.

IssuesThe owner had not planned how to carry the animal in a disaster and had to scramble for equipment. They did not know a transport method based on the crab's breathing and temperature needs, and could easily have assumed more water means safer.

ImprovementKeep a lidded plastic case, stored water, ice packs and paper towels in the emergency go-bag. Plan for feeding and water changes at the shelter, and if the shelter does not accept pets, arrange a place to leave it in advance.

A February morning. The 20 L tank in an unheated room is at 10°C. The 15 cherry shrimp sit motionless on the bottom and do not respond to food. You have no heater. The room warms to 20°C during the day with heating, but turned sharply cold last night. The water tested normal last week.

What is the most appropriate response?

1. Take the shrimp out and warm them in a cup of lukewarm water
2. Buy a tropical fish heater and set it to 25°C right away
3. Wrap the tank in styrofoam or blankets, let the room heating bring it back gradually, and buy a heater to hold 15°C or above. Do not touch them even if motionless, and hold off feeding
4. Decide they have died of cold and dispose of them

AnswerC. Wrap the tank in styrofoam or blankets, let the room heating bring it back gradually, and buy a heater to hold 15°C or above. Do not touch them even if motionless, and hold off feeding

ExplanationCherry shrimp tolerate cold fairly well, but below 10°C their metabolism stops and they go still. Motionless below 10°C is close to an emergency. The correct answer is to insulate the tank, let the room heating bring the temperature back gradually, and hold 15°C or above with a heater. Being motionless is a dormant state, not death. Moving them into lukewarm water causes fatal shock from the sudden temperature difference. Jumping to 25°C is also a sudden change. They cannot digest at low temperatures, so hold off feeding. If they are still motionless after several days once the temperature is back, seek advice.

IssuesThe tank was kept without a heater in a room where the night temperature drops sharply in winter, with no preparation for a cold snap. The owner did not know shrimp's response to cold (motionless = dormant) and could easily have mistaken it for death.

ImprovementIn winter, hold 15°C or above with a thermostat-controlled heater and check nighttime temperatures with a max-min thermometer. Insulate the tank. Remember the rule: when they suddenly stop moving, check the water temperature first, and never warm them rapidly.

A summer-vacation afternoon. A preschool child, saying they wanted to try it, bit into a Japanese freshwater crab raw that they had caught in a river and brought home. There are shell fragments in the mouth and the child may have swallowed a bit of leg. The child is fine now and not in pain. The mother has heard it can be eaten if cooked.

What is the most appropriate response?

1. Have the child rinse their mouth, contact a pediatrician because raw crab can transmit lung fluke, and watch for cough, chest pain and fever for several weeks
2. The child is fine, so observe and forget about it if nothing happens
3. Force the child to vomit to bring up the rest
4. Give a deworming medicine from the medicine cabinet as a precaution

AnswerA. Have the child rinse their mouth, contact a pediatrician because raw crab can transmit lung fluke, and watch for cough, chest pain and fever for several weeks

ExplanationFreshwater crabs are an intermediate host of the lung fluke, and eating them raw causes infection. Symptoms appear weeks later as cough or chest pain, not immediately. The correct answer is to have the child rinse out any remnants, contact a pediatrician for follow-up instructions, and watch for cough, fever and chest pain for several weeks. Forgetting about it because the child seems fine delays diagnosis. Forced vomiting risks aspiration and injury from shell fragments. Over-the-counter dewormers do not work on lung fluke, and self-medicating is dangerous.

IssuesThe family did not know that freshwater crab must never be eaten raw, and kept it within the child's reach. Knowing it can be eaten cooked led to the misconception that a little raw would be fine.

ImprovementTeach children that freshwater crabs are not for eating, and keep the tank where children cannot open it unsupervised. Enforce handwashing after touching, and have the family remember the symptoms of lung fluke (cough, chest pain).

An owner in their 40s kept cleaning the shrimp tank bare-handed with an untreated cut on a fingertip. Three weeks later, although the cut has closed, the finger joint is red and swollen with a lump, and the pain is spreading toward the wrist. Over-the-counter ointment has not helped. No fever.

What is the most appropriate response?

1. The tank water is unlikely to be the cause, so continue the ointment and observe
2. Warm the swollen area with hot water to draw out the pus
3. Add fish medication to the tank to kill the bacteria in the water
4. See a dermatologist, explaining the exposure to tank water, and from now on wear rubber gloves for tank work whenever you have a cut

AnswerD. See a dermatologist, explaining the exposure to tank water, and from now on wear rubber gloves for tank work whenever you have a cut

ExplanationTank water harbors nontuberculous mycobacteria; infection through a hand wound produces joint swelling and lumps weeks later that spread along the lymphatics. Ordinary ointment does not cure it, and the history of tank work is key to diagnosis. The correct answer is to see a dermatologist, mention the tank-water exposure, and always use rubber gloves when you have a cut. Warming does not draw out pus and makes it worse. Medicating the tank only kills the shrimp and does not treat the human infection.

IssuesThe owner ignored the hygiene rule of wearing rubber gloves when you have a cut and did not recognize tank water as a source of human infection. Failing to connect symptoms to the tank delays diagnosis.

ImprovementKeep rubber gloves for tank work and always wear them when you have a cut. Wash hands with soap after working. If skin problems appear, always tell the doctor about your tank work. Family members with weakened immunity should avoid tank work.

A Sunday noon. You poured the land hermit crab's water-dish water and old water from the freshwater crab tank down the kitchen sink, then washed vegetables in the same sink and shaped rice balls bare-handed. Days later, family members have diarrhea and fever, and you have abdominal pain yourself. Droppings had built up in the tank sand.

What should be reconsidered, and what should be done?

1. Tank water may carry Salmonella. Never pour it down the kitchen sink, enforce handwashing and sink disinfection, and mention the pets at the doctor's if symptoms persist
2. Tank water is just water, so it is no problem; the food poisoning must have another cause
3. Dispose of the hermit crab and the crab to eliminate the source
4. Add disinfectant to the tank water and there will be nothing to worry about

AnswerA. Tank water may carry Salmonella. Never pour it down the kitchen sink, enforce handwashing and sink disinfection, and mention the pets at the doctor's if symptoms persist

ExplanationTank water, sand and droppings can contain bacteria such as Salmonella, and pouring them down the kitchen sink contaminates food and utensils. The correct answer is strict hygiene: never dispose of tank water in the kitchen, wash hands with soap after tank work, disinfect the sink, and if diarrhea or fever persists, see a doctor and mention the pets. The misconception that tank water is safe is the root of the incident. Disposing of the animals is unnecessary, and disinfectant in the tank kills them.

IssuesThe owner did not know the rule never to pour tank water down the kitchen sink and went from tank work to cooking without washing hands. Hygiene was lax, with droppings accumulated in the sand, and tank water was not recognized as a source of infection.

ImprovementDispose of tank water in the bathroom or an outdoor drain, and always wash hands with soap afterward. Keep tank equipment separate from kitchen items. Replace sand and water dishes regularly, and be especially strict about handwashing in homes with young children or elderly people.

An August evening. While changing the land hermit crab's artificial seawater dish, you worked bare-handed even though a hangnail on your finger was bleeding. Hours later the finger suddenly swelled and became intensely painful, with redness spreading to the back of the hand. You also have chills. In the summer heat, the seawater in the dish had not been changed for two days.

What is the most appropriate response?

1. It is mild inflammation, so apply over-the-counter antibiotic ointment and wait until morning
2. Soak the hand in seawater to wash it until the swelling goes down
3. Because the redness is spreading rapidly and there are chills, go to the emergency department right now and explain the wound's contact with seawater
4. Cool it, take a painkiller, and see a doctor after the weekend

AnswerC. Because the redness is spreading rapidly and there are chills, go to the emergency department right now and explain the wound's contact with seawater

ExplanationSeawater contains bacteria such as Vibrio parahaemolyticus, which multiply in seawater left standing in summer heat. Infection through a wound swells and spreads rapidly, and with chills there is a risk of systemic infection. The correct answer is to go to the emergency department right now and explain what happened. Redness spreading within hours plus chills is an emergency sign. Waiting until morning with ointment or painkillers is dangerous, and soaking in seawater worsens the infection.

IssuesThe owner did not know the rule to keep wounds out of seawater and worked bare-handed while bleeding. The seawater had been left for two days in summer, favoring bacterial growth. They also did not understand the urgency of rapidly spreading swelling.

ImprovementChange the seawater and freshwater dishes daily, especially strictly in summer. Use rubber gloves for tank work and do not work with an open wound. Wash hands afterward. Decide in advance that rapidly spreading infection means an emergency visit.

A November morning. One Amano shrimp is lying on its side on the bottom, not moving. Its color is normal with no whitening. It was fine last night. Water 22°C, tested fine last week. If it is dead it must be removed before it fouls the water, but it might just be unable to move right after molting.

What is the most appropriate way to check whether it is alive?

1. Take it out, place it on your palm and see whether it moves
2. Look for a molted shell nearby and watch under water for even slight movement of the swimmerets under the abdomen or the antennae. If it responds, leave it untouched by a hiding place
3. Poke it with tweezers to check for a reaction
4. Leave it for a day and remove it tomorrow if its color has changed

AnswerB. Look for a molted shell nearby and watch under water for even slight movement of the swimmerets under the abdomen or the antennae. If it responds, leave it untouched by a hiding place

ExplanationTo check whether a shrimp is alive, watch under water for rhythmic movement of the swimmerets under the abdomen or slight movement of antennae or legs. Right after molting a shrimp may be unable to move and lie on its side; a molted shell nearby makes this likely. The correct answer is to observe without touching and, if it responds, leave it quietly by a hiding place. Out of water it cannot breathe, and if just molted this is fatal. Poking with tweezers injures the soft body. Leaving it a day means that if it was dead it decays and fouls the water.

IssuesThe owner did not know that shrimp cannot move right after molting or how to check for life by the swimmerets. Fearing water fouling from a corpse, they were close to taking a living shrimp out of water.

ImprovementLearn the indicators: swimmeret movement, presence of a molted shell, and body transparency. Observe motionless shrimp under water with a magnifier and check every few hours. Once death is confirmed, remove it promptly and test the water.

11 p.m. on a Saturday. A family member used antiperspirant spray near the tank, and right after, all 20 cherry shrimp went frantic, gathered at the surface, and several flipped over. There is no hospital nearby that treats invertebrates, and at night the phones go unanswered. You have 10 L of dechlorinated water, an air pump and activated carbon.

What is the most appropriate life-saving measure to take right now?

1. Do nothing until the hospital opens and phone in the morning
2. Evacuate survivors to a separate container of clean dechlorinated water at the same temperature, increase aeration and watch in the dark and quiet. Do a full water change of the original tank and wash the media
3. Hold each shrimp by hand in the tank and make it swim to stimulate it
4. Add only activated carbon to the tank and leave the shrimp in it

AnswerB. Evacuate survivors to a separate container of clean dechlorinated water at the same temperature, increase aeration and watch in the dark and quiet. Do a full water change of the original tank and wash the media

ExplanationThere is no resuscitation such as chest compressions for shrimp. In chemical poisoning, saving them comes down to moving them to clean water at the same temperature away from the toxin, supplying maximum oxygen, and letting them recover on their own in the dark and quiet. The correct answer is to evacuate survivors to a separate container, increase aeration, and do a full water change of the original tank, washing the media and substrate. Waiting until morning means losing them all. Handling causes limb loss and injury, and carbon alone lowers the concentration too slowly. When the hospital opens the next morning, describe what happened and the product used.

IssuesThe family had not been told not to use sprays in the room with the tank, and no hospital to consult in a nighttime emergency had been identified. The owner did not know that few hospitals treat invertebrates.

ImprovementBan sprays, insecticides and air fresheners in the room with the tank and tell the family. Research hospitals that treat invertebrates and after-hours contacts in advance and post them. Keep an emergency container, dechlorinated water, air pump and activated carbon on hand.

A March morning. You kept your land hermit crab, which had left its shell and stopped moving, warm on moist sand, but half a day later it is still barely responsive. By phone you found a hospital that treats invertebrates, an hour away by car. The outside temperature is 8°C, and you have moist sand, paper towels, hand warmers and a lidded plastic case.

What is the most appropriate way to transport it?

1. Line the plastic case with moist sand or paper towel, add spare shells, attach a cloth-wrapped hand warmer to the outside for warmth, and carry it in the dark
2. Carry it soaked in the water-dish water to prevent drying
3. Carry it in your closed hand, warming it with body heat
4. Put it in a plastic case with dry sand and turn the car heating up high

AnswerA. Line the plastic case with moist sand or paper towel, add spare shells, attach a cloth-wrapped hand warmer to the outside for warmth, and carry it in the dark

ExplanationIn transporting a land hermit crab, humidity and warmth matter most. The correct answer is a lidded plastic case lined with moist sand or paper towel for humidity, spare shells added, and a cloth-wrapped hand warmer on the outside to hold 20°C or above, carried dark and quiet. Soaking in water drowns it. Gripping it in the hand compresses and dries it. Dry sand cannot hold humidity, and car heating dries the air. Bring notes so you can tell the hospital the temperature, humidity and items used.

IssuesOut of the shell and not moving calls for a same-day visit, yet the owner watched at home for half a day. With no transport kit or hospital information prepared, finding one took time.

ImprovementIdentify a hospital that treats invertebrates in advance and note the contact. Keep a transport kit (plastic case, paper towels, hand warmers, spare shells). Post the same-day visit signs, such as out of the shell and not moving, or body drying out.

A September morning. Your Japanese freshwater crab began molting yesterday morning and has been motionless for a full day with the back of its carapace slightly open. Its legs move slightly but the molt has not progressed. You placed it in a hiding spot, kept it dark and quiet, added mineral supplement at the recommended dose and watched. Water 22°C, water quality normal.

What is the most appropriate action at this stage?

1. Wait another day with the same care before deciding
2. Work the old shell off bit by bit with your fingers through the opening
3. Raise the water to 28°C to encourage molting
4. Stuck mid-molt for more than a day is an emergency sign, so contact a hospital that treats invertebrates right now and transport it in a container with tank water and a hiding place

AnswerD. Stuck mid-molt for more than a day is an emergency sign, so contact a hospital that treats invertebrates right now and transport it in a container with tank water and a hiding place

ExplanationFor molting failure, the basic approach is home care (hiding place, rest, mineral supplement) and watching until the next day, but being unable to move for more than a day meets the emergency sign. The correct answer is to contact a hospital now and follow its instructions. Transport in a container with tank water and a hiding place, dark and quiet. Removing the shell by hand is fatal. Raising the water to 28°C weakens it with heat. Waiting another day is very likely to be too late. If there is no hospital, look for somewhere to consult by phone; failing that, all you can do is continue the same care and watch.

IssuesThe home care was appropriate, but at the point where the visit threshold (more than a day) had passed, a decision was needed, and without a hospital in mind it is easy to hesitate. Not having secured somewhere to consult in advance was the problem.

ImprovementRecord the visit criterion for molting failure (unable to move for more than a day). Look up several hospitals that treat invertebrates and post their phone numbers. When signs of molting appear, hold off on water changes and prepare minerals and hiding places to prevent failure.

A July night. You notice the air pump has failed and stopped. All 20 cherry shrimp in the 20 L tank are gathered near the surface, twitching their legs, and several have stopped moving. Water 27°C, tested normal yesterday. You have no spare air pump, and it is late at night with no stores open.

What is the most appropriate life-saving measure to take right now?

1. Take the shrimp out and rest them on a dry towel in the air
2. Pour in cold tap water all at once to add oxygen
3. Change 1/4 with dechlorinated water at the same temperature, pour the water from a height and direct the filter outflow at the surface to take in oxygen, lower the temperature and stop feeding
4. Turn the tank light up bright and keep observing until the shrimp settle

AnswerC. Change 1/4 with dechlorinated water at the same temperature, pour the water from a height and direct the filter outflow at the surface to take in oxygen, lower the temperature and stop feeding

ExplanationShrimp are sensitive to low oxygen, and the warmer the water the less dissolved oxygen it holds. Gathering at the surface and twitching legs is classic oxygen deprivation. The correct answer is first a water change to bring in fresh oxygenated water, then agitate the surface by pouring from a height or aiming the filter outflow at it to take in oxygen, lower the temperature, and stop feeding to reduce oxygen consumption. In air they cannot breathe, and cold chlorinated water is lethal. Lighting raises the temperature and adds stress. Buy an air pump in the morning, and check motionless shrimp for swimmeret movement.

IssuesThe owner was slow to notice the air pump failure and had no spare. They did not know that summer heat readily causes oxygen shortage, nor any way to supply oxygen other than aeration.

ImprovementKeep a spare air pump and a battery-powered one on hand. Keep the water at 25°C or below in summer and check the aeration bubbles every night. Learn the ways to supply oxygen during an outage or failure (water change, agitating the surface).

1 a.m. on a Sunday in August. The cooling fan has stopped and the freshwater crab tank is at 30°C. The Japanese freshwater crab is up on the land area, motionless; its legs move slightly when prodded. The hospital that treats invertebrates does not open until Monday. On hand you have frozen water bottles, ice packs and stored water (room temperature, 28°C).

What is the most appropriate response tonight?

1. Put ice packs directly in the water and bring it down to 25°C in 15 minutes
2. It is not moving, so conclude it is dead and leave it until morning
3. Do a complete water change with refrigerated water to cool it at once
4. Float frozen water bottles to lower the temperature 1°C per hour, turn on the air conditioning, moisten the land area, watch in the dark and quiet, and consult a hospital in the morning if there is no response

AnswerD. Float frozen water bottles to lower the temperature 1°C per hour, turn on the air conditioning, moisten the land area, watch in the dark and quiet, and consult a hospital in the morning if there is no response

ExplanationFreshwater crabs are animals of cold mountain streams, and 30°C is life-threatening. If the legs respond, it is alive. The correct answer is to float frozen water bottles to cool gradually at 1°C per hour, lower the room temperature with air conditioning, moisten the land area, and watch in the dark and quiet. Ice packs placed directly in the water or a full change with refrigerated water cause fatal shock from the sudden temperature difference. Assuming it is dead because it is not moving and leaving it will really kill it. In the morning, if there is no response, consult a hospital and report the temperature and what happened.

IssuesThe owner did not notice the cooling fan had stopped and was not monitoring the water temperature on summer nights. Freshwater crabs need 18–25°C with cool water changed daily, yet management relied on equipment in a hot room. No holiday contact for advice had been secured.

ImprovementFit a max-min thermometer, and in summer change the water daily and check the temperature. Keep a spare cooling fan and lower the room temperature itself with air conditioning. Always have frozen bottles ready, and find in advance somewhere to phone for advice on holidays and at night.