Hermit Crab Habitat Guide

Creating a “Crabitat”

Hermit crabs are unique pets with complex needs. These little crabs can live for 40 years or more with the right care! At its most basic, a good “crabitat” provides everything your crab needs to thrive. Hermit crabs need a warm, humid environment with deep sand to burrow in, lots to explore, freshwater and saltwater pools to take a dip in, lights, and food bowls.

Choosing a Tank:

Hermit crabs need a deep layer of substrate, usually 6” minimum or 3 times deeper than your largest crab is tall (including the shell). For adult crabs, your substrate will be 12-14” deep! Glass aquariums are the best option to handle the weight of that much substrate. Fish tanks work really well, and while you can start with 5 gallons per crab, as your crabs grow, they’ll need 20 gallons per crab! In the wild, hermit crabs will walk miles in a night, so they’ll love a bigger enclosure to explore.

You’ll also want a glass lid to keep the humidity in your tank. Screen lids give great air flow, but that air flow can remove vital humidity from your crabitat.

Selecting Substrate:

Hermit crabs burrow to molt so they need a nice deep substrate that stays moist and holds a burrow. That’s a lot to ask of substrate! Fortunately, the Fluker’s Hermit Crab Beach Sand Substrate is a premixed substrate available at PetSmart! Another common choice is to use 1 part Eco Earth and 5 parts sand, such as play sand. Avoid fine aquarium sand or calcium sand as these don’t hold a burrow without additional additives.

For small hermit crabs, 6” is a great starting depth. For larger hermit crabs, 12” to 14” is required. You’ll want to moisten the substrate, but it should never be wet. A good way to tell is to take a handful and press it tightly in your fist. It should be slightly crumbly but still hold its shape. If you squeeze and water comes out between your fingers, that’s too wet. If the substrate is wet, that’s considered a flood and requires removing your hermit crabs to replace or dry your substrate. This very wet substrate can drown your hermit crab when they burrow either to molt or to explore.

Heating:

Most hermit crabs prefer to remain in the 80-85°F (26-29C) range. To achieve a consistent temperature in that range, you can use an under-tank heater attached to the back of the tank to radiate warmth into the tank. You’ll use the heater on the back and not under the tank because the heat can’t penetrate through that depth of sand. As a best practice for all heating in habitats, attach the heater to a thermostat with a probe placed slightly above the substrate towards the center of the tank to get an accurate reading. Set the thermostat to turn off at 85°F to keep your crabs nice and cozy.

Humidity:

Most hermit crabs need a minimum 80% humidity but prefer to remain in the 85% range. However, if humidity is too high, condensation can form on the top and sides of the tank and lead to flooding the substrate. Monitor your humidity using a digital hygrometer and if you notice a lot of condensation on the walls, vent your tank by opening the door or the top.

To maintain the humidity, keeping the substrate as above is vital. If that’s not enough to maintain humidity levels, you can add an air pump and air stone to the pools to increase evaporation from the pools and/or add bowls filled with damp sphagnum moss.

Species	Temperature range	Humidity Range
Aussie (Coenobita variabilis)	80-90°F (25-32C)	75-85%
Ecuadorian (Coenobita compressus)	80-90°F (25-32C)	75-85%
Indo (Coenobita brevimanus)	75-85°F (26-29C)	80-85%
Purple Pincher (Coenobita clypeatus)	75-85°F (24-29C)	75-85%
Strawberry (Coenobita perlatus)	80-90°F (25-32C)	80-85%
Tawny (Coenobita rugosus)	75-85°F (24-29C)	75-85%
Viola (Coenobita violascens)	80-85°F (24-29C)	75-85%

Lighting:

Hermit crabs are nocturnal and are most active at night. However, they still need a consistent day and night cycle. Using a timer, you can have the lights automatically turn on and off in 12-hour intervals.

For viewing, LED lights provide a beautiful spectrum and are a long-lasting, low maintenance light fixture. They also don’t provide a significant amount of heat. Incandescent and mercury vapor bulbs do provide heat and need to be monitored closely to not overheat the enclosure.

There are some studies showing that hermit crabs are more active when they have access to UVB lighting. Unfortunately, glass and acrylic block UVB transmission while screen blocks 30-50% of transmission. To best provide UVB for hermit crabs, you’ll need to mount a UVB fixture inside the tank.

Fresh & Salt Water:

Hermit crabs use a combination of fresh and salt water to maintain their health. They need to be able to fully submerge themselves in their water to keep their shell clean and maintain their gills.

For all water, use a water conditioner that removes chlorine and heavy metals, such as Seachem Prime, API Stress Coat, or Thrive Hermit Crab Freshwater Conditioner. This is important for hermit crabs since all invertebrates are very sensitive to metal exposure.

For the freshwater pools, choose a pool that’s deep enough for your crab to submerge but also has decorations or a built-in ramp to make getting in and out easy. Fill the pool with your conditioned water. Many crab keepers use spring water or bottled water. You can use Thrive Hermit Crab Freshwater Solution which is conditioned and safe for your crabs right out of the bottle! Otherwise, always add a water conditioner to tap water before giving it to your crabs.

For saltwater, you can use premixed Thrive Hermit Crab Saltwater Solution or conditioned water and Instant Ocean salt using the directions on the Instant Ocean salt to make a marine saltwater mix. Ideally, you’d check the salinity of this mixture with a hydrometer.

For both pools, you can top them up with conditioned freshwater but unfiltered pools should be completely cleaned weekly and water conditioner added every 2 days to manage ammonia build up (for more information on the nitrogen cycle, check out the Aquarium Water Quality Care Guide).

Many keepers will eventually set up larger pools, where you can use aquarium filters to keep the water flowing and clean. For pools in the 1-2 gallon range, an air pump and a sponge filter connected with aquarium airline tubing can keep the water in those pools clean and clear for much longer. Water changes should still be done every 1-2 weeks. For more information on managing these “mini aquariums” check out Aquarium Maintenance.

Diet:

Hermit crabs are scavengers and typically will eat a wide variety of foods naturally. There are many options for feeding your crabs, from commercial pelleted diets to homemade, custom diets.

PELLETED FOOD: For smaller crabs that cannot pick up pelleted food, feed 1 teaspoon of crushed pellets or powdered food

FRUITS & VEGETABLES: Feed your crab a variety of dark, leafy vegetables such as kale or broccoli, and fresh or dried fruits such as apples, grapes, or bananas. Hermit crabs are sensitive to pesticides so take care to wash your produce prior to offering it or be sure to carefully source your produce.

PROTEIN SOURCES: Hermit crabs love freeze-dried insects, live insects such as waxworms, and freeze-dried single ingredient protein treats for dogs and cats, freeze dried shrimp, frozen krill, and unseasoned, cooked proteins like scrambled eggs or cooked chicken.

CALCIUM SOURCES: To make that hard exoskeleton, hermit crabs need lots of calcium. You can offer items such as cuttle bone, crushed oyster shell, or a calcium supplement (without Vitamin D). Another popular option is cooked lobster, crab, or shrimp exoskeleton.

FATS: Like all animals, fat provides important fuel for hermit crabs and they enjoy being offered a few drops of salmon oil or cold pressed, organic seed oils a couple times a week.

FORAGE: An important enrichment and diet item for hermit crabs is foraging material. This includes worm castings, leaf litter, dried flowers, bee pollen, and green sand. Other popular forage items include star fish, sea urchins, dried kelp, and sand dollars. Always source these from areas free of pesticides and herbicides, without any additives or, for shells and other enrichment items, coatings.

Offer a variety of foods in shallow bowls and change them out frequently to prevent mold or spoilage. Hermit crabs eat small amounts on a daily basis so offer only a pinch of their regular diet per crab and a few small treats. They do seem to enjoy variety so explore your options!

Decorations & Enrichment:

The most important items to add to a hermit crabitat are a variety of shells for your hermit crab to choose from. This “shell shop” should offer at least 3-5 shells per crab that are similar in size to what they’re currently in. You can measure the opening on their current shell and offer shells that are 1/8-1/4” wider at the opening. Measure the shell at the widest point of the opening and note whether it’s a round, nearly circular opening or more of a D shape. Crabs often prefer to keep the same opening types. Make sure to offer different shapes and types of shells as crabs can have definite preferences!

It's important to offer only natural shells. Although pearlized or polished shells can be used, painted, varnished, or resin dipped shells should never be offered to your hermit crabs. Hermit crabs use their claws to make each shell a custom fit and then often eat the discarded shell chips. Paints and varnishes can be toxic if ingested and they also interfere with the normal porosity of the shell that allows some level of gas exchange in the shell.

Once you have a “shell shop” and pools, you can start adding decorations. Aquarium decorations are great in the pools. For the land portions, you can choose fun aquarium or reptile décor. Hermit crabs love to climb and many enjoy elevated shelves, branches or vines to move along. On the ground, they like coconuts or small caves to explore. Another popular feature is a moss pit, using moistened sphagnum moss to give hermits a nice, high humidity resting place.

A fun addition to any hermit crabitat is a hamster wheel. The saucer shaped ones work well for smaller crabs. Many crabs will spend a lot of time on the wheel. This mimics the miles they would walk in their natural habitat looking for food or a good shell.

Bird toys are often safe and fun for crabs. Avoid the metal chains, but many of the toys are crab friendly, made of sweet grass and hemp fiber. These are fun for crabs to climb and shred! Change toys out regularly to keep things interesting for you and your crabs!

Maintaining Your Crabitat:

Hermit crabs will dig and move things around their habitat, so you’ll want to do routine maintenance to move around your decorations, provide new forage items, refresh leaf litter, and remove any waste materials.

Do not disturb the substrate beyond surface level during cleaning. The only time to disturb the substrate will be if you’re moving, upgrading their tank, the substrate has flooded, or you have an infestation of ants or other insects.

Both fresh and salt water should be changed every other day unless they have filtration. In that case, water changes every 1-2 weeks will keep the water clean and fresh for your crabby friends. For more information on maintaining larger pools, check out Aquarium Maintenance.

FAQs

When should I test my water quality?

Water is cloudy
Water smells funny

PetSmart offers free water quality testing and one of our knowledgeable associates can help you get your system balanced.

When should I contact a veterinarian?

Contact an aquatic veterinarian if you notice the following signs:

Decreased appetite or activity
Staying outside of their shell
Excessive molting
Lost claws or limbs
Strong odor from inside the shell

Go to "Find a Fish Vet" at fishvets.org or wavma.org

SHOPPING CHECKLIST

Glass aquarium/terrarium
Secure glass lid or hood with light
Fixtures and bulbs
Thermometer and hygrometer
Marine grade salt
Water conditioner/dechlorinator
Natural sand and coconut coir
Food bowl and two shallow water bowls
New spray bottle
Wood, rocks or other décor (never use cedar or other evergreen wood as it irritates the crabs)
Coconut huts, caves, or artificial plants for hiding
3-5 extra shells per hermit crab
Prepared hermit crab food & cuttlebone
Toys and enrichment items to climb on and investigate
- Ex: driftwood, crab-safe plants, coral pieces, unpainted clay flowerpots.

Ready to learn more?

This guide is a great starting place, but we encourage you to do more research on the individual species that you are keeping so that you can be as successful as possible with your aquarium!