My hermit crab is molting, now what?

You have determined your crab is preparing to molt and you aren’t sure what to do. Do you intend to allow the crab to molt in the main tank? If so there isn’t much you need to do unless you have a surface molt. If you aren’t comfortable allowing a main tank molt, read on. First of all make sure you have your ISO set up and ready to go. This means the temperature and humidity are in the acceptable zones.


Ecuadorian Hermit Crab in its molting burrow


  • Gently move the crab to the ISO tank.
  • Maintain normal cycles of light and dark.
  • Light is critical to a crabs metabolism and that is how they adjust to their environment
  • Place some food and water in the tank.
  • A calcium rich treat is a great idea too.
  • Check the food and water levels daily but do it as quietly as possible.
  • Once the crab is down and not resurfacing, you can remove the food and water until it resurfaces. Hermit crabs have a molt sac that fills with water and sustains them while underground.
  • Leave your crab in peace until he is done with this very exhausting and stressful event.


You may notice a slight odor in the tank. Molting is described by many as smelling like iodine or chemically.Others say it smells similar to death. Don’t be alarmed, that’s normal. The length of time it takes for a crab to molt depends on its size. The larger the crab, the longer it takes. Jumbo hermit crabs could be under for a couple of months. Some hermit crabs seem to like to hibernate long after they are done molting. Do not dig up your hermit crab unless you are sincerely concerned it has died. Digging up a molting crab will kill it in most cases, so you better be sure before you go digging!

Post Molt:

  • When your crab surfaces offer him some food and water, more calcium treats are beneficial
  • Let him remain in ISO another week to make sure he is active and ready to return to the main tank.
  • Gently bathe the crab in plain dechlorinated water to wash the molting scent off of him if you wish.


Molting Article by Sue Latell of

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