This will just be a brief section of items needed in a proper crabitat. If you have all the items listed below, you will have happy, healthy hermit crabs.
I just want to start off by saying don't buy your crabs until the crabitat is setup.
• Enclosure: This is where the crabs will be living for most of their time with you. A ten gallon glass aquarium is great. Ten gallon tanks are great for small crabs as they will have plenty of space to roam around in. The bigger the tank, the better. However, don't go out and by a 100 gallon tank for 3 small crabs. They need space, but they shouldn't get lost. If your housing jumbo crabs, it is absolutely necessary you have a tank size of at least 20 gallons, and preferably more. If you have an old leaky glass aquarium deep in the closets of your basement, you can use that. The "crabitat" will not be holding water except in its own dishes.
• Lid: A lid is beneficial for numerous reasons. The tank will hold in more humidity and heat than having an open top. The crabs will also not be able to escape, which believe me they will if they find a route. Even if you don't have any structures leading to the top, you still need a lid. A glass lid is the best. It holds in heat and humidity really well. You can use a screen lid, however it won't hold in heat and humidity which is vital in a crabs life nearly as well as a glass lid would. You can have a screen lid covered with saran wrap, and that will help hold in heat and humidity. You can even even use a light fixture for fluorescent lights. Another thing is to make sure you have a small open corner for air circulation.
• Substrate: All hermit crabs need to be kept on some sort of bedding. Having no substrate eliminates all natural burrowing behaviors. Your substrate needs to be kept at least twice as high as your largest crab, preferably an inch or so higher. The crab needs to be able to completely bury himself and more. Play sand is probably your best bet. Its great for the crabs as they just love exploring around and digging in it. It provides a nice look to your crabitat, and its easy to get too! Go to home depot and get a 50 lb bag of play sand for $3 versus a 1 lb bag of "hermit crab sand" for $6. An interesting alternative to play sand would be coconut fiber, more commonly known as "Eco Earth" or "Forest Bedding". Eco earth is an excellent burrowing substrate for crabs. They love digging in this stuff. If you have play sand and add in some EE, All the crabs will start digging in it. EE is also fantastic for holding in humidity and moisture. It also naturally breaks down waste. The only downside, it attracts bugs. I'd recommend about a third of your tank being Eco Earth and the rest being play sand. You can also use beach sand instead of play sand. NEVER EVER use wood chips or gravel. Wood chips easily attracts mites, easily molds in the humid crabitat and many woods are unsafe for hermit crabs. While gravel is pretty, it makes digging a real challenge. Stick to a mixture of play sand and Eco earth or just one of those two.
• Heat source: Hermit crabs come form hot tropical environments like the Florida Keyes and the Caribbean. Your house is most likely not warm enough, so an additional heat source is required. You can use an under tank heating mat (a.k.a. UTH), or you can use heat lights. UTH's go on the bottom or side of the tank and warm up the substrate, however if your not housing small crabs than you will have deep substrate and the UTH will be ineffective. Heat lights are great because they can provide UVA and UVB for the crabs and it can simulate natural moonlight with a moon light bulb. However, bulbs usually dry out the tank easier. I'd still recommend bulbs for larger tanks. Proper temperature is around 76 - 82 F (24 - 28 C)
• Dishes: Hermit crabs need 3 dishes. Food, fresh water and salt water. Reptile dishes are now considered the best for keeping hermit crabs as they have a natural look and feel and also provide a way for the crabs to escape. The water dishes should be kept at a depth in which the crab is almost completely submerged. In general my crabs rarely bath but rather sit on top of the dish and drink form there. The crabs however will submerge themselves in order to clean they're body of debris and replenish "shell water" which they carry around in their shell to keep them hydrated. If you have crabs of different sizes, shells, pepples or sponges can be added to provide small crabs a safe way out. However, most reptile water dishes have built in stairs so this won't be necessary.
• Shells: A Hermit crabs' shell is not his own, but rather "borrowed" from other gastropods such as snails. In captivity, extra shells must be provided. A good sized shell is one that's opening is slightly larger than the big pincher. If a crab can withdraw into his shell and seal the opening with his large pincer and third walking leg, its a good fit. However, hermit crabs must change shells from time to time. If the shell is not a good fit, or just for variety. Each crab should have at least three extra shells. One roughly the same size, one larger and one smaller. Its good to have a "shell shoppe" which can just be a small plastic basket filled to the brim with shells. If not enough shells are provided, crabs may fight over shells and the results can be devastating.
• Thermometer: This is just used to determine the temperature in the crabitat, it should be placed near the substrate where the crabs usually are. Whether its a cheap stick on or a fancy digital, a thermometer is vital.
• Hygrometer: Like the thermometer, it should be kept near the substrate and is vital. A hygrometer measures relative humidity (how moist the air is). Humidity should be from 75 - 90% But absolutely NEVER under 70%.
• Shelter: Hermit crabs spend a good deal of their time under shelters. Under shelters, the relative humidity is higher and it is darker where they feel more secure from predators. A shelter can be anything really, coconut huts, ceramic pots on their side, hollow logs, PVC pipes, Fake plants, Anything really. I find that my crabs enjoy looking for hiding spots themselves, such as placing numerous branches together creating a shelter. Usually, the darker the better. In the darkness, the crab feels hidden from potential predators but in the light, it feels exposed. A large, low, small opening shelter can provide plenty of room and darkness for the crabs to enjoy, however they will enjoy any other shelters just as much.
• Climbing objects: Hermit crabs are great climbers, and even creatures as primitive as hermit crabs have a great talent for climbing and can easily climb feats you didn't think was possible. They need to climb to exhibit their natural behaviors and get exercise and entertainment. Besides, wouldn't you want to see your crab in places you wouldn't expect them? There are way too many things for them to climb on so your options are wide. Fake plants, driftwood, mopani wood, Malaysian wood, fig wood, ceramic wood, resin wood, petrified wood, choya wood, cork bark, rocks, coral, water stone, coco fiber walls, fish nets, lego structures, aquarium decor, shelters and even thermometers can be climbed. Filling this requirement should not be that hard.
• Water conditioner: Hermit crabs can not drink tap water. The chlorine can cause permanent blisters on their gills and will cause them a slow painful death. Purchase a tap water conditioner meant for fish. Do not get a water conditioner with slime coat or stress coat. Look for tags like "tap water conditioner" and "removes chlorine and heavy metals". Try and get a water conditioner that has instructions for mixing up one gallon of water. Its easier to have water pre made than having to make it every day. Also look for a water conditioner that has a dropper style format. Do not refrigerate your batch of water.
• Salt: While you may hear that only exotic hermit crabs need slat water, all species need it. Get a package of aquarium salt, not sea salt meant for foods. You can usually find your salt in the fish aisle of the pet store. Again, find one that has instructions for making a batch of water. I'd recommend Instant ocean, Oceanic, Doc wellfish, or Nutrafin aquarium salt. Make sure your salt is not meant for healing fish. If using Doc wellfish or Nutrafin, follow directions for hatching brine shrimp. All water should be served at room temperature.
• Crabs: Don't get one crab, In the wild they travel in packs form 10 - 100+. They generally do well with 3-4. But really, the more the merrier. Its okay to mix different sizes and species, however each species should have another friend of its species, meaning don't have 3 PP's and one E. Hermit crabs perform various group activities. They gather around at the food dish, "talk" to each other, climb eachother, explore new areas together, everything. Besides, when one crab is underground molting, you will have plenty of other crabs to watch and play
Thank you for reading this list! If all these expectations are met, you can insure some happy crabbies!
*** ISO: an isolation tank (or ISO) is a tank meant for bullies, newcomers, and molters. It is simply a smaller version of your tank. I should have a shelter, food and water. When one crab needs to be alone, the ISO is where he belongs for a few days. While not entirely necessary, its good to have one ready.
