How to Care for a Molting Hermit Crab

Updated on July 16, 2019
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Finatics enjoys writing about animal care and is "owned" by a guinea pig, four hermit crabs, three African dwarf frogs, and a betta fish.

What Should I Do If My Hermit Crab Is Molting?

Mainly, what a hermit crabs needs while it's molting is isolation. Although hermit crabs only molt about once every 18 months, if you don’t know what to do when the time comes, it can be very stressful for you and your crabs. Many people suggest making an isolation tank as some crabs may attack the molting one. More importantly, you need to recognize the signs that a hermit crab is molting before you can isolate them.

Signs That Your Hermit Crab Is Molting

  • Your crab suddenly starts digging, although this can be caused if the humidity and temperature are not at the right levels. A crab might dig deeper to insulate himself from conditions he does not like. If it is a crab newly bought, it could be due to stress and a new habitat.
  • Your crab eats and drinks excessively. This is because he’s storing fat and water in a small, gray-black “bubble” on the left side of his abdomen.
  • Lethargy, less activity
  • An ashy exoskeleton
  • Dull, cloudy eyes
  • The crab replaces a missing limb with a gel limb which looks like a little nub where their leg should be.
  • Antennas look tangled and show less activity


Setting Up an Isolation Tank

There are three different options for isolating your hermit crab:

  • Buy another small glass or plastic tank, as long as you can provide the right amount of humidity and heat.
  • If your tank is big enough, you can put a small tank inside the main one, so the temperature and humidity remains the same.
  • Isolate your crab in the main tank.

Option #1

The first option is probably the most expensive, but it guarantees that other crabs will not attack the “molter”. When hermit crabs molt, they are inactive, so they don’t need a very big tank, though it must be large enough to hold a water dish and a food dish. A small one will do—molting is a serious affair! They’re not there to play around, so you do not need to worry about decorating it with things to climb on.

Fill a dish with their regular drinking water and if you want, you can even fill one with saline water since molt-ers need salt to help retain water. Their food dish should have food packed with calcium in it, such as cuttlebone, sand dollars, boiled eggshells, and sea biscuits.

Around six inches of moist substrate should be in the isolation tank so the molter can bury itself. You’ll need to purchase a pet heating pad (unless you already have one) to keep the temperature around 78-80°F and humidity around 78-80% since moisture is essential to molting. To keep an eye on the temperature, a hygrometer and thermometer are also recommended.

You can also add large shells to the isolation tank. And although this isn’t necessary, depending on when you put them in there, the crab might not have enough time to dig in the sand, so they will dive in the large shell and molt there. Darkness is important to molting; studies have shown hermit crabs have healthier molts in darkness, like when they’re under the substrate.

Option #2

The second option also requires another tank, but without another heating pad and other additional supplies. Fill it with substrate, a water dish and food dish, but you don’t need to worry about the humidity or temperature, since it’s inside the main tank!

Lastly, you can isolate your hermit crab inside the main tank. Some people suggest using the side of a bottle of soda to stick inside the sand. As long as it keeps the molting crab isolated from the other crabs, you don’t need to be concerned about humidity or temperature (unless it’s not right in the main tank!). Just make sure that the other crabs cannot climb over the barrier; otherwise it’s useless.

Choosing to Go Without an Isolation Tank

Many people argue it’s best to keep molters isolated, but others disagree. They say hermit crabs should be kept in conditions that stimulate their natural environment- and in the wild, hermit crabs bury themselves for protection against other crabs as well as for darkness. Some also argue that isolation tanks bring unnecessary stress and deep substrate should be enough for the crabs. Whatever you decide to do, this crab should be provided with peace and quiet so he can molt without getting stressed out.


Provide Privacy for Your Hermit Crab

If you suspect your hermit crab is preparing to molt, dig a small hole as big as the crab in the isolation tank and leave him there. Check again in half an hour. If he was serious about molting, he would have dug underneath the substrate already.

When your crab is molting, the best thing you can do is leave him alone. Resist the urge to take a sneak peek at him; you don’t want to stress him out or tear his soft, new exoskeleton. The most you should do is mist the tank every day and replace the food and water. Hermit crabs molt all the time in the wild, so they know what to do. If, for some reason, you absolutely must move him somewhere else, use a spoon to gently move him to a new place.

For How Long Does a Hermit Crab Molt?

Hermit crabs can take several weeks to a month to molt, but wait until your crab acts like himself again, is more active, and has eaten his old exoskeleton (it has plenty of nutrients!) before moving him to the main tank. Molting is how hermit crabs grow; they shed their hard outer-casing and grow a bigger one.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


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    • profile image


      5 days ago

      My hermit crawled face first into another shell and hasn't moved is he molting ? Should I cover him ? Help

    • profile image


      2 years ago

      Please I need help! My crab just molted but I don’t have a shell for it!!!

    • profile image


      7 years ago

      thanks for the news

      .I almost thoght that my hermit crab died!

    • profile image


      7 years ago

      My crab digs a lot but i don't know if it is molting or the temp because the temp isn't perfect. I just can't tell, HELP?!?

    • profile image

      Tessa toutant 

      7 years ago

      I have an odd problem I have two crabs molting at the same time adthey are in the main tank and the other crabs I put in the other tank I seperTed the two molting crabs by a piece of cardboard is that ok it's my first time ever having a crab molt please I need help

    • profile image


      8 years ago


    • RalphGreene profile image


      8 years ago

      I really appreciate this hub, I enjoyed to read it.


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