Hermit Crab Care

Kelly Roper
Pet hermit crab

Hermit crabs make fascinating and unusual pets that, according to the Smithsonian National Zoo (SNZ), can live about 10 years. They're social creatures that like to live with a few companions of their own species. If you can provide the right set up for them, they are fairly easy to care for and very entertaining to watch.

What Do Hermit Crabs Eat?

Fresh Foods

According to the Hermit Crab Association (HCA), these creatures are scavengers and can eat a wide variety of foods, including:

  • Cooked eggs
  • Fish
  • Meat
  • Vegetables
  • Fruits
  • Dried shrimp and plankton (found in the fish supplies section of your local pet supply)

Crushed cuttlebone is also recommended to supply calcium for exoskeleton development.

Commercial Diet

Hermit crabs can also eat a commercially-prepared crab diet. The HCA recommends T-Rex Crab Island crab food since it does not contain the controversial preservatives ethoxyquin and copper sulfate.

Setting Up a Hermit Crab Habitat

A hermit crab's habitat requires very specific items to make it a healthy home for your pet. According to Doctors Foster and Smith, a 10-gallon tank will generally provide enough space for two medium-sized hermit crabs, but it's better to provide even more space if you have the room. Plan to set up the habitat a couple weeks before you bring any crabs home so you can monitor the environment and make sure it's stable enough to support your pets.

Ideal Conditions

According to Foster and Smith, hermit crabs need:

  • 70 to 90 percent relative humidity
  • 70 to 80 degrees Fahrenheit temperature range
  • Part salt water (made with Instant Ocean), part fresh, dechlorinated water

Best Substrates

Substrate is one of the most important parts of any hermit crab's environment. The HCA recommends using a moist, deep layer of substrate that's twice as deep as your largest crab because it's essential for a successful molt.

The best choices include:

  • Sand: This is a natural first choice as a substrate. It holds moisture, it's easy for crabs to move around on and tunnel into, and it helps them molt their exoskeletons.
  • Coconut fiber: Crabs love tunneling through this fiber. It also holds moisture well and is an excellent medium for them to molt in.
  • Crushed coral: This substrate is sold for saltwater aquariums, but it works well for hermit crabs too and provides calcium to help build new exoskeletons during molting.

You can even mix a couple of these substrates together together if you like. This can help you create different levels, with the lower areas staying a bit damper than the higher spots, which provide a place for a crab to dry out a little whenever it likes. The SNZ recommends using a 4:1 ratio of sand and coconut fiber wetted with just enough salt water to give it a packing consistency.

Equipment for the Habitat

You'll need the following equipment for your crab's habitat, and all of it is available in the reptile and amphibians section of most pet supply stores.

  • A hygrometer to keep track of humidity
  • A thermometer to keep track of temperature
  • A screened lid to keep the crab inside its habitat
  • A heat lamp with a 15-watt bulb for light and heat
  • An under tank heater to help keep the temperature stable
  • Three dishes; one for food, and separate dishes for fresh water and salt water your pet can drink and bathe in
  • Sponges for the water dishes to keep up the humidity as well as keep smaller crabs from drowning in their bowls

Habitat Accessories

In addition to the equipment already mentioned, there are a few accessories you can add to the habitat to make it more natural and stimulating. Consider adding:

  • Plants to help keep up humidity and give your pet places to hide
  • Driftwood to create climbing and hiding places
  • Rocks for more climbing and exploring opportunities

Habitat Cleaning Schedule

Regular cleaning keeps the habitat a healthier place for your pet. The following schedule will keep you on track.

  • Scoop poop off the surface of the sand and accessories daily.
  • Change the water dishes daily, and clean all your pet's dishes with a little vinegar and water.
  • Remove and discard all but about one-third of the substrate once every six months, and clean the tank with vinegar and water before setting up fresh substrate. According to the HCA, the third of old substrate you keep will transfer some beneficial bacteria to the new substrate.

Maintaining Hermit Crab Health

Providing a proper diet and habitat are very important for keeping your pet healthy, but there are a few other points to consider.

Molting

According to the HCA, hermit crabs shed their old exoskeletons once or twice a year in order to grow, so they need calcium to grow new exoskeletons beneath the old ones. This is why keeping their habitats at a constant relative humidity level of 70 to 90 percent is so important. Use your hygrometer to measure the humidity, and either add a little water to the lower levels of the substrate to boost the humidity a bit, or add a little extra dry substrate to soak up some excess moisture.

When it's time to shed the old exoskeleton, a crab will burrow into the substrate where it's moist and dark, and it will remain there until the old exoskeleton is shed. You can tell when your crab is ready to molt when its eyes begin to look cloudy and its exoskeleton turns grayish. Once the old exoskeleton has been shed, leave it in the tank because the crab will recover calcium by eating it.

The Importance of Shells

Hermit crabs look tough, but the part of their bodies that remain inside their shells are rather soft. They wear shells to protect themselves, and they hold them in place with small legs on the back of their bodies. As a crab grows by molting, it will need a slightly larger shell to accommodate its new size, so it's a good idea to keep several progressively larger shells available in the tank at all times.

Replacement shells are readily available at most pet supply stores. Try to select natural shells rather than those that are painted and lacquered. Boil the new shell for a few minutes to kill any possible bacteria, and allow it to cool before you put it in your crab's tank. Your crab will switch shells when it feels ready and secure enough to do so. In other words, give your pet some privacy to make the change.

Maintaining Temperature

Temperature plays a big role in proper digestion and overall health. If the temperature inside the habitat dips lower than the ideal 70 to 80 degrees Fahrenheit range, it will slow down the crab's metabolism. If the temperature goes too high, it can literally cook your pet. Check the habitat's temperature in the morning, afternoon, and just before you go to bed to make sure it's in the ideal range and remaining stable. If it's not, you'll need to adjust the heat mat and/or the heat lamp to achieve the proper temperature range.

Handling Hermit Crabs

The right way to hold a hermit crab; © Kelsey Burdo | Dreamstime.com

Crabs are rather delicate, and it's possible to injure them by mishandling them. They can lose a leg, which luckily will grow back, and dropping them might kill them. You can also be injured if you don't hold the crab properly because your pet will pinch you with those big claws, and once a crab pinches, it tends to hang on and is reluctant to let go.

Adults and children should hold a crab in the palm of one hand, with that hand opened flat so the crab doesn't have anything to pinch. The other hand should be held close to keep the crab from falling off if necessary.

It's important to note that crabs shouldn't be handled when they shows signs of entering a molt, and that handling in general should be kept to a minimum in order to avoid stressing the creature.

Hermit Crabs Aren't the Right Pet for Everyone

If you're looking for a pet that will enjoy snuggling with you and jump up happily when it sees you, a hermit crab isn't the pet for you. However, if you can be content watching a crab explore its environment and go through its natural behaviors, you really might enjoy keeping a few of these extraordinary creatures. Check them out at your local pet supply store, and spend some time talking to people who keep them in order to get a better idea whether they are truly the right kind of pets for you.

Hermit Crab Care