Shrimp & crabs

Molting failure (incomplete molt)

SignsStuck mid-molt, half the old shell still attached, lying on its side motionless after molting

PreventionDiet containing calcium and minerals. Avoid sudden water changes or water-quality shifts; provide hiding places

Copper poisoning

SignsSudden frantic swimming, then body turns cloudy white and dies; many die at once

PreventionNever add fish medications or copper-containing fertilizers or chemicals. Avoid water from copper pipes

Pesticide poisoning

SignsDistress right after adding new plants, flipping over, mass deaths

PreventionUse pesticide-free plants, or soak them in a separate container for several days before adding

White muscle disease (muscle necrosis)

SignsAbdominal muscle turns cloudy white, sluggish movement, death within days

PreventionCaused by high water temperature and poor water quality. Keep below 25°C in summer and avoid overcrowding

Ammonia / nitrite poisoning

SignsGathering near the surface, movement stops, legs twitching

PreventionShrimp are more sensitive to water quality than fish. Do not add them for 1 month after setup; test weekly

Land hermit crab desiccation / molting death

SignsOut of its shell and motionless, buried in sand and never emerging, body drying out

PreventionHumidity 70–80% and moist sand at least 10 cm deep for burrowing. Never dig during a molt

Cannibalism / predation wounds

PreventionDefenseless right after molting. Provide more hiding places than animals; keep crabs alone or in a large tank

First aidMove to a hiding place. Legs and claws regrow at the next molt. Bleeding (pale bluish fluid) stops on its own

Lost claw or legs

PreventionDo not catch forcibly with a net. They self-amputate, so never grab a leg. Avoid narrow gaps

First aidDo not handle; keep quiet. Place food nearby. Regrows over several molts, so keep the water clean

Hermit crab fall

PreventionClimbing height under 30 cm. Arrange so any fall lands on sand. Seal gaps in the lid

First aidIf the shell cracks, place several spare shells nearby. If not moving, keep on moist sand, dark and quiet

Sucked into the filter

PreventionFit a sponge over the intake. Baby shrimp are especially easily drawn in

First aidStop the filter, take it apart and rescue them. If alive, return to clean water. Injuries heal with molting

Paragonimiasis (lung fluke)

RouteEating raw freshwater crab; hand-to-mouth after bare-hand handling

PreventionNever eat freshwater crab raw. Wash hands after handling

Salmonellosis

RouteVia hands from tank water, sand or hermit crab droppings

PreventionAlways wash hands after tank work. Do not pour tank water down the kitchen sink

Nontuberculous mycobacterial infection

RouteTank water contacting a cut on the hand

PreventionWear rubber gloves if you have a cut. See a doctor if swelling appears

Vibrio parahaemolyticus

RouteHands exposed to saltwater (land hermit crab seawater dish)

PreventionWash hands after changing saltwater. Keep wounds out of saltwater

Food

• Shrimp: algae and shrimp food every 2 days, only as much as they finish
• Freshwater crabs: fish food, dried sardines and vegetables every 2–3 days
• Land hermit crabs: fruit, vegetables, hermit crab food and a calcium source, replaced daily

Water

• Dechlorinated water at the same temperature. For shrimp, small changes of 1/4 or less at a time
• Land hermit crabs need two shallow dishes: fresh water and artificial seawater

Toys & play

• Willow moss and driftwood to grow algae on
• Climbable driftwood and several spare shells for land hermit crabs
• Both a land area and shallow water for freshwater crabs

Nest, bed & hideout

• Plenty of ceramic tubes, moss and leaf litter to hide in while molting
• Moist sand at least 10 cm deep so hermit crabs can bury and molt

Bedding & litter

• Shrimp: aquarium soil or fine sand. Avoid sudden pH changes
• Freshwater crabs: gravel and stones for land. Change water daily
• Hermit crabs: moistened coral sand, partially replaced monthly

Cage / housing material

Glass or plastic tank. Sponge filter for shrimp; a lid that holds heat and humidity for hermit crabs

Size & space

20 L or more for 10 shrimp. Freshwater crabs: 1–2 per 30 cm tank. Hermit crabs: 45 cm tank or larger

Layout

• Shrimp: layered hiding places with moss and driftwood
• Freshwater crabs: half water 3 cm deep or less, half dry land
• Hermit crabs: deep sand, climbing wood, two water dishes and a shell area

Placement notes

• Escape-proof lid is essential (crabs and hermit crabs climb walls)
• Do not keep in a room where insecticides, mosquito coils or air fresheners are used

Exercise, free-roam & walks

• No walks needed. Taking them out of the tank risks drying, falls and escape
• Keep cleaning and handling minimal; never touch during a molt
• Hermit crabs are nocturnal; observe their activity at night

Temperature & humidity

TemperatureShrimp and freshwater crabs 18–25°C, land hermit crabs 25–28°C

HumidityShrimp and crabs live in water. Land hermit crabs must be kept at 70–80%

Summer & winter

• Summer: cooling fan to stay under 25°C. Change freshwater crab water daily with cool water
• Winter: panel heater keeps hermit crabs above 20°C. Heater keeps shrimp above 15°C

Nail trimming

No nail trimming. Instead, support molting: mineral supplement, calcium source and hiding places

Brushing, skin & coat care

No coat care. Leave the molted shell a few days as a calcium source, then remove it

Other care

Wash food and water dishes daily. Boil hermit crab shells to sterilize and keep several on hand for changes

Protection from predators

• Fish tankmates eat baby shrimp and freshly molted animals
• Heavy lid so cats and birds cannot get in
• Outdoor containers: watch for dragonfly larvae, water striders and herons

Foreign-body ingestion

Keep small shells and shrimp out of young children's mouths. Use unpainted decorations so hermit crabs do not eat paint or glue

Being stepped on

Escaped crabs and hermit crabs on the floor get stepped on. Watch your feet, and move animals to a separate container while cleaning

Getting pinched

Claws and legs get caught in lids or tank rims. If a claw pinches your finger, put it in water and it will let go. Do not pull it off

Falls

Hermit crabs fall from heights and crack their shells. Keep climbing wood low over soft sand. Crabs also climb tank walls and fall

Escape

Dwarf shrimp jump out in strong current; crabs and hermit crabs climb cables to escape. Lid with zero gaps. If found, wrap in a wet cloth to moisten and return

Safe release procedure

1. Put the pinched hand, crab and all, into water (warm fresh water for hermit crabs)
2. Hold still and wait; it will let go on its own
3. If it does not, gently support the rear of the body to prompt movement
4. Once free, return it gently to the tank

After the release

Wash the wound under running water and disinfect. A freshwater crab pinch carries no lung fluke risk, but see a doctor if it swells

What to tell the vet & what to bring

Few hospitals treat invertebrates, so check in advance. Report water temperature, water test values, anything added and any chemicals used

Checking consciousness, breathing & heartbeat

• Any slight movement of legs or antennae
• Shrimp: rhythmic movement of the swimmerets (under the abdomen)
• Hermit crab: does it withdraw when the shell is touched

Stopping bleeding

• Pale bluish fluid stops on its own in clean water
• Lost parts regrow at the next molt; keep water clean to prevent infection
• Hermit crab with a cracked shell: place spare shells nearby

Transport

• Container with tank water and a hiding place (moss), kept dark
• Hermit crab: keep moist and warm with damp sand or paper towel