Does a hermit crab have to have sand when it is molting?

It depends on the size of your hermit crab. They can take as little as one week, up to several months. The average time for a smaller crab is 3-4 weeks, but can take much longer, so don't be tempted to dig them up if they are under for a very long time.

While molting under the surface, your crab is shedding his old exoskeleton. His new exoskeleton needs some time to harden, and then he will eat his old exoskeleton. He needs this as it helps him replenish the calcium and protein to help his new exoskeleton harden and to give him energy. He may surface before his new exo is fully hardened. He may appear pale, and lethargic. Do not disturb him at this time. Wait until he is acting normal, with normal energy and color, before you pick him up and play with him. He needs time to recover without being disturbed.

Make sure you provide him with plenty of protein and calcium and chitin sources after he surfaces, such as shrimp with the tail still on, dried mealworms, freeze dried shrimp (without preservatives, ethoxyquin and copper sulfate are toxic to hermit crabs). Give him a little honey or coconut (unsweetened) in his dish for some added energy.