How do I know when my hermit crab needs a new shell?
Just as we outgrow our clothing, crabs outgrow their shells. Prior to molting, a crab reabsorbs some of the calcium carbonate from the old exoskeleton, then secretes enzymes to separate the old shell from the underlying skin (or epidermis). Then, the epidermis secretes a new, soft, paper-like shell beneath the old one.
How do crabs change their shells?
Heat & light
If you use an under-tank heater, cover it with at least an inch of bedding, so your crabs don't get uncomfortably hot. Hermit crabs thrive at humidity levels between 70% and 80%. Mist their terrarium with non-chlorinated water as necessary and use a hygrometer to keep track.
How do you help a hermit crab?
Re: Trapped in shell
If I were you I would either do what you did or gently dip the crab in distilled water and slowly move him back and forth (to try and loosen his abdomen so he could get out).
What to do if your hermit crab is stuck in its shell?
Can you help a hermit crab molt?
How do I know if my hermit crab is sad?
Can I move my hermit crab while molting?