Hermit Crabs, Done Right (Not a Fridge-Magnet Pet)

Colony Animals

Hermit crabs live in large groups in the wild and are more active and confident with company. Keep at least two, and more if you have the space.

Humidity and Heat

Hermit crabs breathe through modified gills that must stay moist, so dry air harms them. Keep humidity at about 70–80% or higher and temperature at about 75–85°F (24–29°C). A glass enclosure with a mostly covered lid holds humidity. Put any heat source on the back or side above the substrate, never underneath where crabs bury themselves, and control it with a thermostat. Measure with a digital thermometer and hygrometer.

These are typical ranges from keeper guidance. Check with a specialist keeper for your species.

Deep Substrate for Molting

Crabs bury themselves to molt, sometimes for weeks. Give at least 6 inches (15 cm) of substrate, or three times the height of your largest crab, whichever is deeper. A mix of sand and coconut fiber, damp enough to hold a shape without water dripping out, works well.

Molting: Leave Them Alone

A molting crab is soft and vulnerable. Don't dig it up. Keep the enclosure humid and calm until it resurfaces, and leave its old exoskeleton for it to eat.

Fresh and Salt Water

Give two dishes deep enough for crabs to dip in, with an easy way out: one of dechlorinated fresh water and one of dechlorinated water mixed with marine aquarium salt (not table salt). Avoid metal dishes.

Spare Shells

Crabs change shells as they grow. Offer several natural, unpainted shells per crab, in a range of sizes slightly larger than their current ones. Painted shells can flake, and crabs dislike them.

Diet

Hermit crabs are scavengers. Offer a varied diet: fresh fruit and vegetables, leaf litter, unsalted nuts and seeds, a protein such as dried shrimp or unseasoned cooked egg, and a calcium source such as cuttlebone. Remove uneaten fresh food daily.