If you have hermit crabs or are thinking of adopting, please read the full care guide below to ensure that you know everything possible to provide for these complex creatures.
- First up, the crabitat! Unless you live in the tropics, you’ll need a tank that keeps humidity in – none of the wire cages you may see at souvenir shops. The bare minimum tank size is 10 gallons for two small crabs. As they grow, you’ll need to keep upgrading. A good starter size for medium crabs is about 30 gallons. If the tank has a mesh lid, you can cover it with plastic wrap to keep in moisture. Just leave a little bit open at the ends for air circulation.
- Fill your crabitat with a suitable substrate – sand, coconut fiber, or a mixture of both (NO gravel). The bedding should be moist but not drippy and about 6 inches deep for medium crabs. Hermit crabs burrow into their bedding to molt, and the tunnels they make should be able to hold up on their own without caving in. Hermit crab sand at the pet store gets dirty and smelly fast; it’s best to use playsand from the hardware store, or just plain old beach sand. If you opt for the latter, please make sure you bake it to kill any bacteria to which hermit crabs have no immunity.
- Any water that enters the crabitat (their water dishes, their bedding, their misting sprays) must be treated with a dechlorinator that removes harmful chlorine and chloramines, which can kill crabs. You can find a dechlorinator at any pet store.
- Fill your crabitat with lots and lots of hiding places and climbing surfaces, like hemp netting and wood. Any naturally found wood should be boiled and allowed to dry out before being placed into the crabitat to remove any parasites or harmful bacteria. Click here for a list of safe and unsafe woods. They also love coconut fiber mats hanging from their walls. Keep a close eye on any natural accessories for mold, which can be fatal if allowed to run rampant in your crabitat, and remove them at the first sign.
- As residents of the seashore, hermit crabs need access to salt water along with fresh drinking water. Prepare two dishes, one with de-chlorinated tap water and one with de-chlorinated water with added marine aquarium salt, which you can find in the saltwater aquarium section of your local pet store (NOT table salt – this is poisonous to them). Dishes should be deep enough for crabs to submerge their shells but not too deep that they cannot get out. If unsure, put some rocks or other objects to help them in and out of the dishes. Keep these dishes clean and replace water weekly.
- Food! Most commercial hermit crab foods contain preservatives and other additives that are dangerous to crabs. Ethoxyquin is a common preservative in these foods and is poisonous to crabs. Instead, hermit crabs should receive a variety of fruits, veggies, grains, nuts, seeds, etc. (a healthy human diet!). Make sure to supplement with plenty of brightly colored veggies like carrots for carotene, and buy a calcium supplement to sprinkle over their food from your local pet store. For more information on feeding, please click here. Visit this page for a list of foods that are toxic to hermit crabs (like onions).
- Provide lots of extra shells of various sizes (larger than your current crabs) that are NOT painted (the paint can be toxic to them) for your crabs to try on. As they grow, they’ll need progressively larger shells. Without a sufficient supply, crabs may fight among themselves for the best shell.
- Purchase a thermometer and a hygrometer to measure temperature and humidity, respectively. The temperature should average around 80 degrees F and never drop below 75. To maintain it, you can use a tank heater on the side of the aquarium (not under the sand, as it will not penetrate the bedding) at one end. Another option is to use 15 watt reptile lamps, alternating day and night lamps, at one end of the tank only. That way, the crabs have a gradient and can move to the colder side if they need to. You can increase the wattage for larger aquariums. It is also thought that providing UVA/UVB lighting is beneficial for hermit crabs because it more closely mimics their natural environment. When using these lights, be sure to place them directly over the wire mesh without plastic coating between the light and the tank, as plastic and glass can filter out the beneficial UVB rays. Note also that crabs can overheat if subjected to temperatures over 85 degrees for too long, so be very careful about monitoring the temperature when using external sources of heat.
- The humidity should never drop below 70% and should hover around 75-80% (but much higher, and it can promote mold growth). To achieve this, spray daily/as needed using a spray bottle/mister with de-chlorinated water. Remember, if hermit crabs don’t have high enough humidity, they will be unable to breathe and will slowly suffocate.
- Keep the top layer of substrate clean by removing droppings weekly and cleaning out uneaten food at least every other day. Sometimes hermit crabs will carry food to their hiding places, so be sure to check those. You should not need to deep clean and replace more than the top layer of the substrate more often than a few times per year, unless you have a problem with mites or other bugs.
- MOLTING: Molting is an interesting phenomenon in which crabs will bury themselves underground for several weeks to 1-2 months several times a year to shed their exoskeleton and grow a new one, allowing them to grow, as their skin doesn’t stretch the way ours does. Crabs who are preparing to molt may exhibit different behavior, such as excessive digging and eating, and may have a dull color to their legs and claws. Once a hermit crab goes underground to molt, he must NOT be disturbed. Doing so could kill the hermit crab in his vulnerable state. Simply leave him be and wait, no matter how hard it is. You will know if your crab has died during molting, as you will begin to smell a rotting scent. Only if that occurs should you dig up your crab. If another crab appears to be excessively disturbing the site of the molting, consider transferring that crab into a separate isolation tank, set up with all the same amenities, temperature, and humidity, until the molting process ends, so that the crab doesn’t pose a threat to the molter.
- Never adopt only one hermit crab; they require socialization. Watch your crabs closely when introducing them and separate them if they appear to begin fighting over shells (i.e. one crab climbs on the back of another crab and begins trying to pull the crab out of his or her shell). Sometimes, crabs might emit a “chirping” sound as they establish the social order – this is normal. When adopting a new crab, always isolate the crab in a separate tank for at least a week to ensure that he is healthy and happy before introducing him to your main tank.
- Never pull a hermit crab out of his shell or pull him off of something to which he’s clinging fiercely. Hermit crabs will allow themselves to be ripped apart before abandoning their shell or a safe space. They can regrow limbs, but sometimes the damage is too great, and the crab will die.
As you can see, keeping hermit crabs happy and healthy is a complex business. These little guys are not toys and should not be given as gifts to small children who cannot properly meet their needs.
Finally feel ready to adopt?
Check out our cheat sheet to the left to print out all the basics as you set up your crabitat. When you’re ready, please choose adoption instead of purchasing a crab who’s been ripped from the wild. There are thousands of crabs who need homes like yours! Consider checking out the Hermit Crab Association, a great network of folks serious about hermit crab care. Their forum is a wonderful resource for connecting potential adopters with crabs in need nearby. Visit it here.