These crabs are active and sociable, so adopt more than one. Accordingly, get the largest glass or plastic tank possible. The absolute minimum is 10 gallons, which could house two small crabs, but you’re better off with a 20-gallon or larger tank. Other essentials are two water bowls, one for salt water and one for fresh, a food saucer, a heat source, sponges, shells, sand or another suitable substrate, a shelter, a plant mister and something for the crabs to climb on, such as twigs or baskets.

Heat and Humidity

Check the exact requirements of your species, but the hermit crabs you’re most likely to have need a warm damp habitat, with a temperature of about 75 to 85 degrees Fahrenheit and a relative humidity of about 75 percent. Use a hygrometer to monitor the humidity and a thermometer for temperature. Misting the tank and substrate increases the humidity instantly, while additional damp sponges help maintain it. Additional heat can be supplied with a heat bulb (not a heat lamp for reptiles, which is dangerous for hermit crabs) or a heat mat underneath one side of the tank.

Mobile Homes

As your hermit crabs grow, they’ll need bigger shells, so provide a selection of shells slightly larger than the ones they already have. As with other decorations, sterilize the shells before offering them to your crabs. Boiling tends to be the easiest and safest way to do this. Brush off any dirt and debris first. Use a glass pan if possible and boil the shells for at least 20 minutes.

Crab Cuisine

Hermit crabs are omnivores, consuming a great range of plant and animal foods. A commercial hermit crab food makes a good basic diet, but supplement it with fresh vegetables, whole grains and small amounts of meat, fish or boiled egg. Use a calcium supplement for crabs as per the instructions -- like other arthropods, hermit crabs need a lot of calcium to form their hard exoskeletons. Along with a varied diet, hermit crabs need water, both fresh and salt. Always use dechlorinated or bottled water for your pets, not water straight from the tap. Use an aquarium salt mix to make up water for the salt water bowl, which hermit crabs need to maintain the right salinity in their bodies. If you have small crabs, place sponges in the water bowls so your pets don’t drown.