How to Take Care of Hermit Crabs (Part 2: The Crabitat)

How to Take Care of Hermit Crabs (Part 2: The Crabitat)

If you haven’t read the first part of this series on how to take care of hermit crabs, check out our introduction. In this blog, we’ll discuss how to set up your crabitat.

The Basic Crabitat

Acrylic terrariums are the best habitats for pet hermit crabs because they trap humidity, but fish tanks and reptile aquariums also work fine. If you just have 2-4 small hermit crabs, a 10-20 gallon tank will do just fine. Upgrade to 20-40 gallons for 3-4 large crabs.

For the substrate (what you put at the bottom of a tank to mimic the earth), you can use damp sugar-sized arrogate sand like the kind you would use for a sandcastle. Larger grains might cut your hermie’s feet! Other options are compressed coconut fiber expanded with salt water, which can also work as food, or fine-grained crushed coral. The crabs need to be able to dig in whatever substrate you use, either to hide or molt, so don’t just buy aquarium gravel! Make sure the substrate reaches 3-5 times the height of your largest crab, or about 15 cm.

You need to use dechlorinated water with hermies, since chlorine can harm them. You can buy tap water conditioner or just use spring water. When making salt water, use marine salt from a pet store rather than table salt, which often has iodine poisonous to hermies.

Best Conditions

Hermit crabs need 70-85% relative humidity in their tanks. Any higher and mold will start to grow, and any lower, the crab will actually suffocate! Although their terrestrial (land) creatures, they have gills instead of lungs, so they need enough moisture in the air to breathe.

You want to invest in a hygrometer to make sure your crab can breathe. They will live in lower humidity for a few months, but will look lethargic because they’re actually suffocating to death slowly and painfully. This might be the most important consideration to make when setting up your crabitat. That being said, you still want some fresh air coming in.

Putting natural moss (not Spanish or decorative) or sponges (but they get dirty easily) in the tank can increase the humidity if you soak them in dechlorinated water. You can also dig holes in the four corners of the tank and add ¼ cup of dechlorinated water to each one.

You want the temperature to stay at 75-85 degrees, like the tropical climates where these crabs are often from. Without enough heat, the crabs’ metabolisms will slow down too much. Overhead lights (not UV) or a heater can keep the temperature up, but make sure they don’t dry out the substrate.

You need to put both fresh and salt water dishes (no metal) in the tank, deep enough so that the crab can get water into its shell, but not so deep that they drown. It’s also important to have a slope with grips like sponge, shells, or pebbles so that the crabs can climb out easily.

Now For the Fun Stuff!

Hermies love to play by climbing, so add toys like wicker baskets, choya logs, legos, rocks, shells, plastic reptile toys, sand blasted grapevine, driftwood, coral, and barnacles. Make sure none of the toys reach high enough that your crabs can escape, though! Boil all toys to disinfect them before you put them in the tank. If a toy is organic, make sure you don’t put it directly in the substrate, or mold will form. Make sure none of the toys have chrome, nickel, arsenic, cadmium, evergreen wood, or paint.

Equally important are hiding places if your crab gets scared or stressed or starts to molt. Use half-coconut shells, broken pots, large seashells, hermie huts, and half-logs. Adding plants like bamboo, venus fly traps, bromeliads, and spider plants will make the tank feel more like their exotic home.

Perhaps the most important fun things to put in your tank are extra shells. You need 2-3 shells per crab. Try to find ones of different sizes, but all a little bigger than the crab’s current shell. Natural shells (no paint) with round or oval openings are preferable.


Finally, we just want to reiterate that it takes a lot of work to set up a nice crabitat. If you’re willing to invest this initial time in your pet, the day-to-day maintenance is fairly quick and simple. And of course, the reward is well worth the effort! Stay tuned for our last installment on how to take care of hermit crabs.