Hermit Crab

(Coenobita—many species in this genus are known as hermit crabs)

Land hermit crabs come from all over the world and make a fun, exotic pet. When properly cared for, they can live for as long as 20 years in captivity! They are social creatures and thrive with at least one other crab for companionship. Although half of their bodies are covered in a hard exoskeleton, they have soft abdomens that they coil into the chambers of a seashell for protection. As they grow, they must find a bigger shell, leading to many different “looks” over their lives!

Depending on species and age, hermit crabs range from .25″ long to the size of a softball!

Hermit crabs are scavengers and will eat just about anything. Provide your crabs with bits of meat or fish, any kind of fresh fruits or vegetables, hardboiled eggs, popcorn or natural peanut butter. Don’t feed them the same thing two times in a row, and avoid feeding them anything spicy or anything with preservatives. Also make sure to change their food every day: hermit crabs bury uneaten food, which leads to molding.

A minimum 5-gallon glass aquarium with a lid makes a good “crabitat”-old or leaky aquariums are perfect! Choose a larger tank if you will be housing many crabs together. Include plenty of places to hide and toys to climb on: pieces of driftwood, cholla branches, coconut husks, coral or terracotta pots. Also provide them with a selection of empty, unpainted shells—they will need to find a new one when they molt.

The substrate should be at least 2 to 3 times as deep as your largest crab. Use play sand mixed with coconut fibers and add enough dechlorinated salt water to reach a “sand castle” consistency. Do not use wood chips: the sap can be toxic to hermit crabs.

A hermit crab has a hard exoskeleton that does not expand, so in order to grow, the crab needs to shed its exoskeleton. It will usually bury itself while the process takes place—DO NOT dig up your crab while it is molting! Your crab will need extra calcium during this process; leave the molted exoskeleton in the tank for the crab to eat. Also provide calcium-rich foods like cuttlebone, egg shells, ground oyster shells or shrimp with the exoskeleton still on it.

Make sure the crabitat stays between 72 and 85°F. An under-tank heater is best; overhead lights can dry out the tank very quickly.

Humidity must be kept between 70 and 80%. Any less and the crab’s gills will dry out, causing it to die. Keep the substrate damp, and mist wood or terracotta items in the crabitat daily to maintain humidity. Also provide two non-metal bowls of dechlorinated water: one of fresh water and the other of salt water (use sea salt, not table salt). Make sure they are deep enough for the largest crab to wade through and bathe. Keep a sponge or small pebbles in the bowls so that smaller crabs can get out.

Myths vs. Facts

  • Myth: Hermit crabs are crabs.
    Fact: Actually, biologically speaking, hermit crabs are more closely related to lobsters, shrimp and crayfish than to true crabs.
  • Myth: Hermit crabs are solitary animals.
    Fact: In the wild, hermit crabs live and travel in large groups. As a crab grows, its discarded shell can become available for a smaller member of the group, so finding a good shell at the right time becomes easier for group members. Its name comes from the fact that it lives alone in its “house,” like a hermit in a hermitage.

Please note, articles in the Animal Resource Library are for reference only, and are not meant to diagnose or treat any medical or behavioral issues your pet may be experiencing.