Congratulations! You've chosen a unique and exotic animal to be your pet. With basic knowledge and care, your land hermit crabs can live for many years. Whatever your reasons for owning them, you will find they are a clean and friendly pet.
One of the lesser-known facts about land hermit crabs is that you don't have to worry about catching anything from them. This makes them an excellent pet for a person with allergies to animal fur and dander. Hermit crabs are crustaceans, not reptiles, and as such do not carry or transmit and potentially harmful bacteria, such as Salmonella.
Your pet hermit crab is a friendly animal, compared with the "regular" kinds of crabs. For example, a ghost crab you find on the beach will never let you pet its back or handfeed it. If you've ever caught a ghost crab, you know that it tries to pinch you every chance it gets! In comparison, land hermit crabs are quite friendly. After your crab becomes used to your scent and habits, it will come out of its shell with minimal coaxing.
In addition to being clean and friendly, your hermit crab is by nature an active and curious pet. Hermit crabs are nocturnal, which means they are most active after sunset. In the wild, land hermit crabs are most active from 8 p.m. to midnight, with activity gradually tapering off towards dawn. They do not "stick" to this schedule, however; a cloudy day or a rain shower can bring them out during the day.
When darkness falls, your crab comes out of its shell and starts moving around its cage. If you sit quietly beside the cage, you'll observe your crab eating, drinking, and interacting with its cagemates. The crab will scurry about in the cage, leaving behind a comical set of "clawprints." The crabs really seem to enjoy climbing; long-time hermit crab owners report seeing their crabs walking across the screen lids covering their cage. Tiny crabs have been observed using their small claws to grasp the silicone sealant in the corners of an aquarium and, by climbing claw-over-claw, reach the top of the aquarium and escape. So for your crabs' enjoyment as well as your own, provide them with items they can climb on, dig under and explore. Hermit crabs are very strong for their size, too--don't be surprised if your crabs decide to rearrange their home overnight!
The first thing your pet will need is a place to call home. The best home for a pet land hermit crab is a glass aquarium. This fact has been tested and proven true by scores of successful crab owners. The reasons for the aquarium's popularity are many: It maintains a constant temperature inside; it retains humidity well; it won't melt if used with an under-tank heater; it is difficult for the crabs to escape from; and it is available in a variety of shapes and sizes to suit the beginner with two crabs. Aquariums can be fitted with a glass lid, which then transforms them into miniature tropical habitats that are similar to the crab's native home.
The alternatives to the aquarium are many. The most common one is the clear plastic box-type enclosure often sold under the name "critter keeper." This type of enclosure has one major flaw: the lid. Hermit crabs MUST have an adequate amount of moisture present in the air or they can't breathe. The standard lid of a "plastic aquarium" is made of hard plastic mesh, which does not retain humidity well. This can be remedied by placing some plastic wrap over the lid, leaving a small corner open to allow for air exchange. The size of the cage and its construction make it fine as a temporary home for your hermit crabs, but for their well-being, you should look into purchasing them an aquarium.
A second alternative to an aquarium is the wire cage. These cages are usually made of wood or plastic and hardware cloth. The wire cage works as a permanent home ONLY in tropical areas. If you live in a temperate area, you should not, by any means, keep your crabs in a wire cage. The reasons not to are many. First, wire cages are open on all sides and do not retain humidity. Also, some wire cages are not constructed well, and may fall apart while you're carrying your crab. A fall from a height greater than a few feet onto concrete or a similar hard surface can kill a hermit crab.
The second item you will need for your new pet is some type of substrate to put in the bottom of its tank. There are many substrates currently on the market:
Sand. Sand is a good substrate, as it has many qualities that hermit crabs favor. By far the best quality of sand is the ease with which the hermit crabs can bury into it. Hermit crabs love to dig in sand, and, given sand that is slightly damp, will construct a fascinating underground maze of tunnels and hideouts. The Ecuadorian species actually digs itself a molting pit in the wild, and covers itself with sand. Like all things, though, sand has some negative qualities. It is rather messy and seems to end up everywhere when you are bathing the crabs or cleaning their "crabitat." If it gets damp and stays that way, it can sprout mold, which is detrimental to the crabs' health. Many people's crabs (to their owners' dismay) seem to think it is a "game" to tip the water dish over each night into the sand. Finally, some hermit crabs just plain don't like sand, and will spend hours obsessively grooming each grain of sand from their bodies. The least expensive variety of sand sold is "play sand," which is normally used for filling children's sandboxes. 25 pounds of play sand costs about $2.50 in your average hardware store. A step up from play sand is aquarium sand, which pet stores sell for use in marine aquariums. The most expensive type of "sand" is actually pure calcium carbonate. It is sold under the trade names of Vita-Sand and Calci-Sand. It is very good for your hermit crabs because of its high calcium content. Because it is prohibitively expensive for some ($8 per small bag in some areas), some crab owners provide their crabs with a dish of it as a calcium-rich occasional treat.
Gravel. The kinds of gravel available to the hermit crab owner are seemingly endless. Hermit crabs prefer gravel with a texture that is smooth to the touch. There are many grades of gravel, from nearly sand grade up to pebble-sized stones. Sharp pieces of it actually can scratch a crab's exoskeleton, so try to get the smoothest grade available. Gravel is available in all the colors of the rainbow, and it is safe to use colored gravel, as long as it isn't dyed with water-soluble dye. Some gravel manufacturers have used the dye found in powdered drink mixes to color their gravel. To avoid this type of gravel, always look for the phrase "aquarium safe." To be on the safe side, you can avoid colored gravel all together and go with natural gravel. No matter what kind of gravel you ultimately choose, since hermit crabs cannot see colors, they won't appreciate your neon-pink gravel any more than they will appreciate a slate gray hue. The top-of-the-line gravel is that which is made of crushed coral or shell. This gravel is sometimes called "reef sand" or "dolomite." It is more expensive, but like the pure calcium-carbonate sand discussed previously, it is worth it if you can afford it.
The past few years have seen an explosion in the reptile trade. More people than ever are keeping reptiles as pets, and pet suppliers are constantly creating new and better products for these hobbyists. This has been both a blessing and a curse for land hermit crabs. Most hermit crab care products are now sold in the reptile area of many pet stores, and it is sometimes difficult to discern whether or not a product made for a gecko will be beneficial for your land hermit crabs.
In the case of substrate, there are some reptile-recommended substrates that do not work well with land hermit crabs. Most reptiles require a warm, dry habitat for optimum health. Hermit crabs, on the other hand, need a warm, moist habitat. Substrates made of ground nutshells are made with the dry habitat in mind, and when they become wet, tend to clump together and mold. Dry, dehydrated pieces of nutshell are porous, and will cling to and absorb water from any surface, including land hermit crabs--literally "sucking" the much-needed moisture from the crab's exoskeleton.
Water is, without a doubt, the very most important element of hermit crab care. Simply put, the crabs cannot survive without it. Moisture is critical for the crabs to be able to breathe and molt successfully. Land hermit crabs breathe with their modified gills and through the thin skin on the underside of their abdomen. Both of these must be kept moist to function. The crabs are moistened in the wild by warm, humid air and by frequent rainfall. It is very important that the humidity inside a crabitat be maintained at a beneficial level. The lowest amount of relative humidity a crab can tolerate is roughly 50%. In contrast, the average household's relative humidity is 30-40%. There are many things a crab owner can do to raise the level of humidity in the crab tank.
The basic rule of thumb for land hermit crabs' drinking water is this: Do not give the crab any water you would not put in a tropical fish tank. This means that you'll probably need to remove the chlorine and other harmful chemicals from the water prior to giving it to your crab. Bottled and filtered water are also acceptable, but usually more expensive. Plus there is no way of guaranteeing that during processing (with bottled water) that the chlorine was adequately removed or (with filtered water) that the filter you're using wasn't clogged or contaminated.
Removing the Bad Stuff: Chlorine.
Chlorine is harmful to land hermit crabs. Repeated exposure to it causes blisters to form on the crabs' gills, resulting in suffocation and death. You can remove this harmful chemical by purchasing from your pet store a general dechlorinizer (or tap-water conditioner). It's relatively inexpensive and usually comes in a dropper-style bottle. You do not need to buy a large amount of it (in fact, you shouldn't, because the drops may gradually lose the ability to dechlorinate the water if stored for a long period of time). Try to get a brand with instructions on how to mix only ONE GALLON of dechlorinated water, otherwise you'll have to do some calculating as to how many drops per quart, etc. Read the instructions on the bottle or packaging. Usually you'll need something like 1 drop per gallon (if the dechlorinizer is really strong) or 5 drops per quart. Check your individual brand, though, because the amount per brand can vary significantly. Put the required amount of drops in the bottom of the gallon (or 1/2 gallon) jug and fill it up with water. Let the water sit open overnight after treatment, to be sure all the chemicals are neutralized. Once you've dechlorinized the water, it can be served to the crabs in practically any non-metallic, non-porous container.
The two things you need to consider when selecting water dishes for your crabs are how much water it will hold, and how deep the container is. If you have large crabs, you will need a larger container, obviously. Hermit crabs like to drag themselves (shell and all) into the water dish and just sit there sometimes. They may be replenishing their "shell water" or they may be cleaning out their shells. It's important you check the water dish daily, and make sure that it is clean and full of water. To clean the water dish, run it under the tap and dry it well with a dishcloth. The best water dishes for hermit crabs are molded plastic or cement reptile-type dishes that look like rock, sea shells (which are good because a small amount of calcium leaches into the water and this is beneficial for the crabs), plastic jar lids and individual-serving-size small glass casserole dishes. NEVER use anything metal as a water dish. Land hermit crabs are extremely sensitive to metal.
Be sure your water dish is not so deep that your smaller crabs will drown in it. If you have large crabs and small crabs together, put a natural sea sponge in the large crabs' dish so a stray small crab will have an "island" to sit on in case it stumbles into the large dish. Smaller water dishes and jar lids don't need a sponge in them, but a sponge is critical if you're using a large clamshell, which may be very deep toward the middle-back areas. If the water seems deeper than your smallest crabs, don't take the risk. Put a sponge into the dish.
You may notice when you refill the crabs' water dishes that there is sometimes a slimy residue in the bottom of the water dishes. This "scum" is probably the residue from the (traces of) oil that is used in many of the commercial crab foods. This oil is used since hermit crabs need a bit of it in their diet. However, this does not mean to add extra oil to their crab food or feed them extra oil, which could be deadly to your little friends. Another culprit could well be the oils from the natural foods (such as the coconut, etc.) you feed your crabs. The scum is probably a residue of this oil, combined with food particles and other items the crabs drag into the dish along with them. It is no cause for alarm. Just scrub out the scum using a damp paper towel (no soap or cleanser).
In the wild, land hermit crabs eat a wide variety of foods: fallen fruit, decaying wood, leaf litter, plants and grasses, and items washed ashore by the tide. They aren't fussy eaters by nature and have even been observed eating fecal matter. Hermit crabs locate food in two ways: by smelling it and by seeing other crabs eating. One way you can test this is to set a dish of one of the smellier "treat" options listed below into their crabitat. Watch as they come out, wiggle their antennae, and make a beeline for the treat dish. No one is exactly sure of hermit crabs' nutritional requirements to survive; but crabs have been kept for long periods of time being fed a staple diet of commercial food supplemented with occasional treats.
You should feed your crabs a good commercial food, which you can get at PETCO. If you choose to feed your crabs a pelleted food, be sure to crush the pellets before giving the food to your crabs. Very small crabs cannot grasp the pellets with their claws.
A recent study found that land hermit crabs prefer to have a different food each time they eat. While this may not be practical, you should offer your crab a variety of foods. Some other foods your crab may enjoy as occasional treats are fruit (except acidic fruits such as citrus or tomatoes), especially tropical fruits that crabs would find in their native habitat: mangoes, coconuts and papayas. Vegetables (except starchy vegetables such as potatoes), nuts, applesauce, raisins, trail mix, peanut butter, honey, cooked egg and meat, fresh fish and shellfish, cereal, crackers, washed leaves and bark of deciduous trees, washed grass, and popcorn. Some people notice their crabs are partial to "junk food" such as corn chips, sugary cereals and pretzels. Though they may like these foods, they should of course be limited to occasional treats.
The best treats for land hermit crabs are, of course, natural foods. You'll find a number of wholesome natural treats in your local pet store: frozen fruit and plant-based iguana food, freeze-dried and sun-dried shrimp and plankton, seaweed (normally sold to make sushi or in health-food stores), brine shrimp (drained first of salt water), fish food flakes, and fish vegetable flakes
With a little practice, you can handfeed your hermit crab. Take a piece of apple or grape and hold it one hand while you use the other hand to coax the crab out of its shell and place the food near the crab, underneath its two pinchers. Usually the crab will do a "taste test" first, by sticking an antenna into the food and then putting the antenna into its mouth. Patiently wait for the crab to taste the food, and then see if it uses its small claw to break off a piece of food. He passes the food to the third set of maxillipeds (mouthparts) and then on into the mouth. If a crab is not interested in eating, it will pinch the food and move it around, but not bring any food to its mouth. Set the crab down if it isn't interested; land hermit crabs operate on metabolism only, and you cannot "convince" it to eat if it is not hungry, whether it's your pet's favorite treat or not!
Most pet stores that sell hermit crabs also have small sea sponges for sale. Sometimes the crabs are sold with a kit consisting of a small plastic carrier, crab food, and a sponge. A large (baseball-sized or larger) natural sponge in a dish with water in it, close to or over the substrate covering the under tank heater is a very effective means of dispersing humidity into the air. The sponge helps to pump the humidity into the air better by providing a larger surface from which the water evaporates. You might compare it to how quickly a kitchen sponge dries out as opposed to the time it takes a dish of water to evaporate.
The key to using the sponges is to have a couple of them, so they may be switched out on a regular basis to prevent any mold or bacterial growth. A thorough rinse in hot water only and a short soak in a sea salt solution, followed by a rinse with some dechlorinated water helps to clean the sponges. Squeeze out the extra water and allow them to air dry. If additional disinfecting is needed, place the sponge in the microwave for two minutes when it's completely dry. Don't put it in the microwave when they are moist (or even damp), or it will quickly shrink to the size of a walnut. Large natural sponges can be expensive, and the upkeep of them is mandatory. Since they sit in water and the crabs crawl on them, they are an ideal breeding site for bacteria that could kill your crabs.
Source: Hermit Crab Association