How to Recognize When a Pet Hermit Crab is Sick. Hermit crabs are pretty resilient animals, but they may become sick at some point. You should observe your pet hermit crabs on a daily basis to recognize the first signs of sickness.
Spend a few minutes each day checking on your hermit crabs. Make a note of which crabs are digging, burying themselves or climbing. Also, look for any crabs losing legs, running around without a shell or not retreating into their shells. Those are the main signs a hermit crab is sick.
Observe any crabs that are losing legs. When adjusting to a new environment, it is normal for a crab to loss a leg or two. If at any time, one of your pet crabs begins losing legs quickly, he is probably sick.
Check for mites, which appear as white or brown flecks on the crab. You can usually see them crawling on the crab. While not necessarily a sickness, mites are not good for your pet.
Isolate any hermit crab that will not curl up in its shell. This crab is probably sick, and you don't want your other pets to get sick.
Recognize that when hermit crabs become inactive, their habitat may not be suitable, which can cause them to become sick. Even in proper environments, your crab may become sick and inactive.
Inspect your hermit crabs for mold or fungus. If you find any on your crab, you should isolate the crab and bathe it. You should also provide a new shell in case your pet wants to switch to a cleaner shell.