Hermit Crab Care Sheet

Hermit Crab Species Overview

Hermit crabs are nocturnal crustaceans that enjoy digging and scavenging for food.

Pet hermit crabs thrive when kept in groups of two or more. In nature, hermit crabs can be found in colonies of hundreds! 

Like other crustaceans, hermit crabs have a hard outer layer of skin called an exoskeleton. Hermit crabs will shed, or “molt,” their exoskeletons regularly as they grow. Before molting, hermit crabs will prepare by eating and drinking more than usual. 

Unlike other crab species, hermit crabs cannot produce their own shells. Instead, they use empty snail shells to protect their soft bodies. Be sure to provide each hermit crab with at least three to five empty shells in assorted sizes that they can move into as they grow. 

Pet hermit crabs should never be released into the wild. It is unlikely that they will survive, but if they do they can damage the local ecosystem. 

Hermit Crab Characteristics 

Difficulty of Care	Beginner
Average Life Span	10+ years with proper care, depending on species
Average Adult Size	2–6 inches long, depending on species
Diet	Omnivorous
Minimum Habitat Size	10-gallon glass tank for 1 or 2 hermit crabs

 

Hermit Crab Handling

To avoid being pinched or injured, pick up a hermit crab by the back of their shells. Hermit crabs should always be held over a soft surface to prevent injury if they’re accidentally dropped. 

Children of all ages should be monitored while handling a hermit crab. 

Avoid handling pet hermit crabs while they are molting—molting is highly stressful for hermit crabs, and handing them during this time can lead to fatal injury.

Hermit Crab Supply Checklist

Pet parents should have these basic supplies on hand for their hermit crabs: 

• Appropriately sized habitat 

• Commercial hermit crab food 

• Treats 

• Substrate 

• Moss 

• Mineral blocks or cuttlebone 

• Food and water dishes 

• Salt or commercially prepared saltwater 

• Water conditioner for hermit crabs 

• Hideaway place 

• Climbing decor 

• Plants 

• Low-wattage nocturnal bulb 

• Under-tank heater 

• Additional shells as your hermit crab grows 

Hermit Crab Habitat

Choosing the Right Enclosure 

At a minimum, up to two adult pet hermit crabs can be housed in a 10-gallon glass tank. If more hermit crabs are added to the habitat, each crab should have at least 5 more gallons of extra space in the tank.  

All habitats should be secured with a tightly fitting lid to prevent escape. Glass tanks are preferred over plastic ones, since glass is better at retaining heat and humidity. 

Pet hermit crab habitats are ideally placed in a quiet, low-traffic area of the home. Keep habitats in a draft-free area that’s not near an air conditioner or in direct sunlight. 

Hermit Crab Habitat Mates 

Despite their names, hermit crabs are social animals that thrive when kept in pairs or groups. Remember: Every pet crab added to the habitat will need 5 additional gallons of tank space. For example, a group of four hermit crabs should be housed in a 20-gallon or larger habitat. 

Pet hermit crabs should be introduced to each other gradually and under close supervision to ensure they are compatible. If two crabs fight, separate them. Never keep different species of invertebrates in the same habitat. 

Temperature 

The warm end of a pet hermit crab’s habitat should be kept at 80 F, while the cooler end/nighttime temperatures should be around 70 F. Pet parents must check the temperatures of the habitat daily. Two thermometers—one in the warm area and one in the cool area—should be placed in the enclosure so  both zones can be checked at once. A digital point-and-shoot thermometer can also be used to instantly read habitat temperatures. 

Light and Heat Sources 

Hermit crabs are ectotherms, cold-blooded animals that rely on external heat sources to regulate their body temperature. A low-wattage incandescent bulb should be used to provide small amounts of light and heat to the pet hermit crab’s habitat. In most cases, the habitat will also need an under-tank heater to maintain an appropriate temperature in the habitat’s warm end (80 F). 

The wattage needed for the heat bulb will vary depending on the size of the enclosure, the distance of the bulb from the crab, and the ambient temperature of the room in which the enclosure is kept. Adjust the wattage of the bulb to maintain the recommended temperature gradient within the tank.

Note: Some light bulbs provide not only light to the tank but also heat and/or ultraviolet (UV) light. Pet parents should check the light sources they are considering, so they know exactly what their function is in the tank. 

Under-tank heating pads must be connected to a thermostat and covered with at least 1 to 2 inches of bedding to prevent the crab from getting burned. 

Heat sources should be attached to a thermostat to keep temperatures within a safe and comfortable range. 

Hot rocks should never be used; they can get too warm and cause injury. 

Hermit crabs are nocturnal. To maintain a healthy day/night cycle, low-wattage bulbs should only be kept on for 10–12 hours a day. At night, turn off lights inside the hermit crab’s enclosure or switch to a nocturnal or infrared light. 

Humidity 

A pet hermit crab’s enclosure should have a humidity level of 70 to 90%. A hygrometer (humidity gauge) should be used to measure the enclosure’s humidity daily. 

Hermit crabs need humidity in their environment to stay hydrated and keep their gills moist so they can breathe. If the humidity in a pet hermit crab’s enclosure falls too low, hermit crabs will suffocate and die. Pet parents should maintain humidity levels by misting the enclosure with dechlorinated water daily, or more often if needed. 

Water Bowls 

Pet hermit crabs need constant access to two non-metal, non-porous dishes of water that are shallow enough for the crab to enter comfortably. One water dish should be filled with fresh dechlorinated water, while the other should be filled with saltwater with a specific gravity (salt level) of 1.021–1.026.  

The water inside the bowls should be no deeper than ¼ to ½ inch, depending on the hermit crab’s size. A natural sea sponge should also be placed inside each bowl to help the crab climb in and out easily, and to prevent accidental drowning. Sponges should be disinfected and changed regularly to prevent fungal and bacterial growth. 

Substrate 

Hermit crabs are natural-born diggers! The bottom of a pet hermit crab’s enclosure should be lined with a layer of substrate that’s deep enough to protect a hermit crab’s delicate body while they dig, burrow, and molt. As a rule of thumb, the substrate should be at least three times deeper than the height of the largest hermit crab in the enclosure. 

Commercially available sand, mixed with coconut fiber bedding in a 5:1 ratio, is ideal. Sand must be washed, dried, and sterilized before use to ensure its pathogen-free. Moss can also be added to the mixture to boost humidity. 

Sand should be kept moist enough for the particles to clump together but not be too wet. 

Avoid wood shavings, such as pine and cedar bedding, as they have oils that can irritate pet hermit crabs’ skin and respiratory tracts and cause illness. 

Decor and Accessories 

Shells

Unlike other crab species, hermit crabs cannot produce their own shells. Instead, they use empty snail shells to protect their soft bodies.  

Be sure to provide each pet hermit crab with at least three to five empty shells (commercially available) in assorted sizes that they can move into as they grow. 

New shells should be a bit larger than the hermit crab’s current shell. 

Before being offered to a pet hermit crab, shells should be boiled for five minutes, drained, and left to cool completely. 

Make sure the shells are fully intact and do not have any cracks or holes. 

Painted shells are not recommended. The paint can flake off the shell and may impede the shell’s ability to regulate humidity. Even non-toxic paint can change the way a shell feels to a crab, which can cause them stress. 

Climbing Decor

Pet parents should create places for their pet hermit crab to climb by adding:

• Branches

• Logs

• Driftwood

• Lava rock

• Plastic plants

• Coral

To keep crabs stimulated and interested, rearrange their tank’s decor or add new climbing places to their enclosure every now and then. 

Hiding Areas

A pet hermit crab’s enclosure should have several safe places for the crab to hide during the day. 

Hermit Crab Cleaning and Maintenance

Pet parents should spot-clean their hermit crab’s habitat daily by using a small kitchen strainer or mesh fish net to remove any waste droppings, discarded food, and pieces of molted exoskeleton (the hard, protective layer of skin that covers a hermit crab’s entire body). A pet hermit crab’s habitat must be disinfected and cleaned thoroughly at least once a week. 

To clean a pet hermit crab’s habitat, take these steps: 

1. Move the hermit crab to a secure environment. Remove any décor, accessories, and substrate (if used) from the habitat.  

2. Scrub the empty tank and any furnishings with pet-safe terrarium cleaner or 3% bleach solution. The bleach solution should stay on the habitat for at least 10 minutes to ensure that the surfaces are properly disinfected. If using a commercial habitat cleaner, follow the manufacturer's instructions.  

3. Rinse the habitat and accessories thoroughly with water, making sure to remove any trace amounts or residual smells left by the cleaning agent or bleach solution.   

4. Allow the habitat and its contents to dry completely before placing new substrate (if used) and clean accessories into the habitat.  

5. Return the hermit crab to the clean habitat.  

Sponges also need to be disinfected once a week to prevent fungus and bacteria from forming. To disinfect sponges, take these steps: 

1. Rinse sponges in hot, running tap water. 

2. Rinse sponges in treated saltwater and then in dechlorinated water. 

3. Squeeze out any excess water and allow sponges to dry completely before being added back to a hermit crabs tank. 

4. If the sponge is very dirty, it can be squeezed out, left to dry completely, and then microwaved for one to two minutes. Ideally, pet parents should have several sponges on hand so they can switch them out when one is being cleaned. 

Hermit Crab Diet and Nutrition

As omnivores, hermit crabs enjoy a range of foods, including:

• Commercial hermit crab diets

• Fruits

• Vegetables

• Nuts

• Brine shrimp

Pet hermit crabs also need a calcium supplement to help keep their exoskeleton (the hard, protective layer of skin that covers a hermit crab’s entire body) healthy. Hermit crabs should always have access to both fresh and salt water. 

Hermit Crab Feeding Guidelines 

Hermit crabs need to be fed once daily. 

Food and water bowls must be made of a non-metal and non-porous material, such as hard plastic or ceramic. Hermit crabs are extremely sensitive to metals, and porous materials cannot be disinfected properly. 

As hermit crabs are nocturnal, feeding sessions should take place at night. Uneaten food should be removed from the enclosure the following morning. 

Hermit crabs take tiny bites and eat very slowly. 

A well-balanced diet for a pet hermit crab includes high-quality, commercially available food formulated for hermit crabs, fed once a day. Use the manufacturer's instructions to determine how much food should be given daily.  

Pelleted foods should be crushed before feeding, especially for small crabs. 

Uneaten food should be discarded and replaced before each feeding. 

Fruits and vegetables may be offered as occasional treats. 

Fruits and vegetables should be washed in purified, distilled, or bottled water before being offered to a hermit crab. 

Vegetables naturally high in carotene (including carrots and untreated marigold flower petals) can help hermit crabs maintain their exoskeleton’s red-orange hue. 

Vegetables can be offered six to seven days a week and may include:

• Spinach

• Carrots

• Kale

• Romaine lettuce

• Bell peppers

• Cucumbers

Fruits should be offered no more often than one to three times a week. Fruits may include:

• Mangoes

• Coconut

• Papaya

• Strawberries

• Apples

• Bananas 

Nuts, seaweed, brine shrimp, and fish flakes can be offered as occasional treats (no more than two to three days a week). Crab-safe nuts include:

• Hazelnuts

• Chestnuts

• Almonds

• Macadamia nuts

• Pecans

• Walnuts

Nuts are high in fat and should be fed sparingly. 

Pet hermit crabs need a calcium-rich diet to maintain the health of their exoskeleton, especially during molting. Pet parents can add a powdered calcium supplement to their hermit crab’s food or feed them a crab-safe natural source of calcium, such as crushed cuttlebone. 

Pet hermit crabs need constant access to shallow bowls of saltwater and freshwater. The water inside each bowl should be shallow enough for the hermit crab to enter and exit easily.

Pet Hermit Crab Care

Hermit crabs are highly social! These crabs are happiest when kept in pairs or small groups. 

Pet parents should place their hermit crab in their saltwater dish once a day. Instead of removing the crab from the dish, allow them to exit in their own time. 

Molting

Hermit crabs molt one to two times a year. Molting is the process of shedding an old exoskeleton to make room for growth. Depending on the crab’s size, it can take days or weeks to complete a molt. 

While molting, hermit crabs bury their bodies in the sand. Never try to move or dig up a pet hermit crab that’s begun to molt, as it can seriously injure or kill the crab. 

After molting, hermit crabs eat their old exoskeleton to absorb its calcium. Other pet hermit crabs in the tank may try to fight the newly molted crab for their exoskeleton. In this case, it’s best to move any other crabs to another tank, away from the crab that just molted. 

If more than one crab lives in the same habitat, pet parents can place a divider over the molting crab to protect them. To create a divider, push a dry, clean, 2-liter soda bottle into the sand. Be sure to remove the bottle’s cap before adding it to the tank. 

Note: Other homemade dividers can be dangerous, as molting crabs may try to climb them and fall, injuring their delicate bodies. 

If necessary, hermit crabs can also be separated from other crabs and moved into another habitat while molting. However, molting crabs that have already buried themselves should not be dug up. After molting, newly molted crabs should only be returned to their original habitat once they have eaten their old exoskeleton and their new exoskeleton has hardened. 

Hermit Crab Veterinary Care

Annual Care

Pet hermit crabs should be seen by a veterinarian once annually. Small transport carriers can be used rather than moving their entire enclosure, but be sure to bring photos of their enclosure and supplies for the veterinarian to assess as part of the exam.

Signs of a Healthy Hermit Crab

• Intact shell

• Successful molts with no stuck shed

• Good appetite

• Active and curious, especially at night

• Intact shells of an appropriate size and material

When to Call a Vet

• Lethargy outside of molting

• Staying out of a shell

• Stuck molts

• Missing limbs or claws

• Strong odor

• Anorexia (not eating)

• Visible parasites

Common Illnesses in Hermit Crabs

• Stuck molt

• Missing limbs or claws

• Ectoparasites such as mites