Hermit crabs. Cute little critters, the inventors of the “mobile home”. Over 1100 different species inhabit many different environments, from deep sea bottoms to the tops of palm trees. They have adapted to all kinds of habitats, but we’re going to focus on the ones most commonly kept as pets, the land hermit crab.
The genus Coenobitidae has 17 species, and more than one are used in the pet trade, the most common three are the Caribbean (purple pincer), the Ecuadorian and the Australian. Regardless which one you are keeping, the basic requirements are very similar.
All hermit crabs have gills. They require water to allow them to breathe. Most will use salt water for this purpose, so ensuing a source of proper salt water is important for their well being. The reason I said “proper” salt water is that it isn’t as easy as adding table salt to water to make something that is the same as the ocean. Seawater contains 70 trace elements and minerals, not just sodium chloride (salt). And while “sea salt” may sound like it would be OK, it isn’t. The drying process actually drives off many essential trace elements. There are commercial marine salt mixes available that are used in keeping salt water aquariums, so it is rather easy to find an appropriate salt mix to use.
They also require fresh water to drink. So, a proper Hermit Crab habitat will contain two separate water dishes. Ideally, they should be able to immerse themselves in the bowls, but they should at least be large enough so that they are not easily emptied or turned over as the curious crabs hunt through their environment.
They all come from hot, humid environments. So, it is key to their health to mimic that. Which is something you can’t do in a little plastic tank with some sand/gravel in the bottom. You should have at least a 10 gallon aquarium, a heat source, and a moist substrate (bottom). I like using a mix of coconut husk and sand, giving the animal the ability to dig and bury itself, especially when it is approaching a molt.
Most crabs die from not being able to molt properly, not from old age. A little plastic box is not suitable for long term care of them, as it cannot provide the essentials for proper molting. Unfortunately, a large number of Hermit Crabs are sent home in totally inappropriate habitats, only to die a slow tortured death.
Kiosks pop up in malls selling these interesting little critters, and then disappear just as fast. The cuteness of them with their little comically painted shells, and the relatively low cost of the too small enclosures encourages impulse purchasing. Some purchasers do a little research after, and invest in making a proper habitat for their new pets. Far too many don’t, making for the crab to be a effectively a disposable pet. It is not wholly the buyers fault, as a consumer, they trust what they are told. But in caring for any live animal, we should do the proper research first, and not fall for gimmicky marketing.
Hermit crabs can be wonderful pets that are low maintenance, affordable and long lived, but only if the proper habitat is provided. You can get complete, unbiased care information at: https://en.wikibooks.org/wiki/Animal_Care/Land_hermit_crab .