By: Kristin Valdes, DVM

Hermit crabs are fascinating pets that, despite their names, are very social.  They are also a pet that requires a lot of work and care.  If you are interested in a hermit crab, consider finding books at your library to read up on this pet.  There is a lot to know!

Hermit crabs can be fairly difficult pets for a first time pet owner.  They are social over time, but require an adjustment period to feel comfortable with their new owner.  If the introduction is rushed, they can become stressed and ill enough that they can die.  Hermit crabs like having other hermit crabs to live with.  A hermit crab requires at least one companion, but the more hermit crabs the better for these social critters to interact with.

A 20 gallon tank will work well for 2 small hermit crabs.  A 40 gallon tank is better for several hermit crabs, or for 3 full grown adult hermit crabs.  Large hermit crabs and small hermit crabs can live together without problems if they have enough space. They require a humidity of the environment at 75-85% relative humidity.  Purchase a hygrometer to measure this.  If they do not have enough humidity, they will suffocate slowly and die.  They breathe through hardened gills that need moisture in order to function.  Not enough moisture means they cannot properly get oxygen. They do not require baths unless you cannot get the humidity to the 75-85%, but baths are far less preferable than the ideal humidity.  A bath once to twice weekly will be required if humidity not obtained.
If the enclosure becomes contaminated and you see any insects in the tank, which can sometimes happen, you will need to completely clean out the enclosure.  You cannot use any pesticides or mite treatments, as this will kill your hermit crab.
Glass can be cleaned with white vinegar as needed.

The enclosure should have a temperature of 75 to 85F.  To reach this temperature, use an under tank heater with a built-in thermostat to ensure the appropriate temperature is reached.  It is important to do further specific research, as each of the 6 common species of hermit crab has an even more specific temperature preference within this range.   No basking lights are required as long as the under tank heater has maintained an appropriate.

The material you want at the bottom of the enclosure should be about 3-5 times the height of your largest hermit crab.  The substrate should also be dampened– if sand, it should be the consistency ideal for building a sandcastle.  You can use sugar-sized sand.  Marine aquarium coral rock sand and gravel are other substrates, along with a finely ground coconut fiber-based bedding for reptiles (e.g., Forest Bedding)– the coconut fiber may be used during molting.  In the hides in the enclosure, you can use reptile moss to help with moisture.  Change the moss frequently– at least every week– to prevent mold buildup.  Spot clean the tank daily for poop and food scattered around the tank.

2 water bowls are always needed: a bowl of fresh dechlorinated water and a bowl of salt water (dechlorinated aquarium salt for marine fish; DO NOT EVER USE EPSOM SALTS OR TABLE SALT) are always needed in the enclosure.  Natural clam shells are a great choice for bowls of water.  If they are not available, you need to find a bowl that your hermit crab can climb in to and submerge themselves completely, with a shallow side that is easy for them to get out, and a deep side in which they can soak. If the bowl has no easy way for them to climb out or if the sides are too smooth, place pebbles on one side to help them climb out.
To dechlorinate the salt and fresh water, a dechlorinator like Zoomed water conditioner can be purchased.  You simply add it as directed to the water.  Prior to placing the water in the tank, let the water sit out at room temperature for at least a day.    Some people have a 2 gallon milk container filled with fresh water, which they add dechlorinator to, and another 2 gallon milk container filled with salt water and dechlorinator. These are then used daily for the fresh water and salt water refills.  Alternatively, you can use spring water.  It is important to make sure nothing is added to the bottled water, like magnesium, as this can kill a hermit crab.  The specific gravity of the salt water should be 1.020-1.023.

Don’t offer commercial food- it’s not very good because it often has preservatives, and several are often not safe for hermit crabs.  Hermit crabs should be offered food daily, and it should consist of protein, fruit, and vegetables.
For the protein source, you can offer things like fresh shrimp, silver sides, krill, and bloodworms.  Sardines and meal worms are other meat sources. Occasionally, meat like steak or chicken (without any seasonings) can be offered.  The meat can be raw, cooked, or freeze-dried, but it should have no salt or preservatives.
You can offer several different fruits like blueberries, mango, banana, pineapple, grapes,  and apple. For vegetables you can offer carrots, corn, spinach, and broccoli heads.
Maple leaves are also ok as long as the lawn and trees have not been treated with pesticides or fertilizers.  For treats, you can offer walnuts, sweet potatoes, peanut butter, fresh rose or sunflower petals, honey, oatmeal and wheat germ.
Be sure to wash all fruits and vegetables before feeding them to your crabs, and use de-chlorinated water to do it. Always do everything you can to keep your crabs away from chlorine. Vegetables and plant matter such as oak or Remember to change their food daily, otherwise they will bury uneaten food, which gets the tank dirtier faster.

Hiding places are needed for your hermit crabs.  These should include half logs, halved coconuts, and even clay flower pots that are cut in half long wise.  Other pet store hides work well too, so long as your crab won’t get stuck in the hide.
In addition to hiding places, offer them several things on which to climb.  Dried choya wood, stumps, driftwood, coral, and barnacles provide great climbing and exploration for crabs. Please do not use any pine wood as the oils the wood contains are irritating.  Natural seaside items are also good to use once  they are sterilized by boiling them in dechlorinated salt water.
Shells are also very important for your hermit crabs– they are a necessity.  Offer many shells in the enclosure similar to the size your hermit crab is using– but just slightly larger.  Check what species your hermit crab is, as some species of hermit crabs prefer round shell openings and others prefer oval openings.  Place 3-5 shells in the enclosure for each of your hermit crabs, so they can choose the shell that works best for them.  Don’t use painted shells.  These can lead to death of hermit crabs by toxins associated with the paint.

Boil all shells in dechlorinated water every 2 weeks to keep them clean and free of mold or debris.  Clean the entire enclosure monthly and remove all substrate.  If the glass is dirty, clean it with vinegar and water as well.

If your crab digs under the substrate for a couple of weeks, this is because your hermit crab is likely molting; don’t worry. For several weeks, he will need to be left alone.  Do not change the tank while this molting is occurring, unless you begin to smell a very foul smell, which indicates your crab has died.  During the molting, he will need to be left alone; if he is bothered, the stress could kill him. This molting is so he can grow.  The shed exoskeleton will be eaten by your hermit crab, then he will come out from the burrowing to find a new shell to fit into.

When they get home, be patient and don’t interact too much right away.  Leave them alone in their new enclosure for a few days, changing only the food and water daily.  When they stop hiding in their shells when you pass by, wait another few days, then try to hold your hermit crab.  Let them explore your hand and get adjusted to you.  Soon, they will look forward to the interaction.

Feel free to call us with any questions at (502) 241-4117.