How to Tell if a Hermit Crab is Dead or Molting
Many people assume (wrongly) that when a hermit crab molts it simply travels from one shell to another, as such when they see their hermit crab out of its shell and curled into a lifeless ball, they may think it is dead and throw it in the garbage. This is a bad mistake, as the lifeless looking hermit crab may be alive; molting can take weeks to months.
Molting or Dead?
Just before a hermit crab molts it typically eats a lot and drinks a lot, and may appear to be collecting water. It may also appear lethargic. It is not uncommon for a newly purchased crab to want to molt. Sometimes the loss of a limb will make a hermit crab molt sooner than it normally would but typically they molt every 12 to 18 months.
Most hermit crabs molt under the sand, and their tank should be at least 6 inches (15cm) deep with sand, however most people only provide an inch or two which forces them to surface molt. Some hermit crabs surface molt even when provide with the right amount of sand, mostly due to possibly not having a proper enclosure at some point in their life, however surfacing molting in the wild would not be safe so it is not natural.
Hermit crab experts may even have two tanks, one with shallow sand that would be their regular habitat, and a special isolation tank with 6 inches, or more, of sand.
In molting the hermit crab comes out of its shell, it collects bits of water and slowly it sheds a layer of skin. The skin often turns white before being shed.
If you find your molting hermit crab out of its shell on the surface and have other crabs in the tank you need to protect it. The best way is to cut the top off a 2 liter pop bottle in half and place it over the crab, pushing it into the soil so other crabs cannot dig under. If there are no other crabs simply leave it be and monitor it. Darkness is preferred for the molting crab.
The shed their exoskeleton and normally eat it.
If your hermit crab buries itself for molting it may remain buried for some time, even more than a month. Resist the urge to dig it up. The sand should be kept moist to the consistency of that you would use for building a sandcastle, but not wetter.
If your hermit crab is dead it will stink. If it has surface molting you can remove it when you smell it. If it has buried itself, wait at least 2 months before digging it up or your curiosity could kill it. Many hermit crabs are discarded when molting due to the owner mistakenly thinking they are dead.
Provide your hermit crab with at least 6 shells, 1 smaller than it requires, 3 correct size, and 2 much larger, sometimes they will crawl into the opening of a larger shell and molt there.