Bizarre question about hermit crabs?!?!

[reefnewbi]

Hello everyone! I have a 3 gallon tank with 4 hermit crabs and this happens about 2 times a month but with different crabs. Ill wake up or come back from work and one of the shells will be empty and ill see what appears to be half a dead hermit crab on the bottom of the tank. The first time this happened i thought the crab had died. But to my amazement the next morning the crab would be back in the shell as if nothing had happened. Is this some kind of molting or shedding of the skin? Really interested to your answers?

 

[mfinn]

The crab probably molted and that's the part you saw on the bottom of the tank.
The crabs shell is very soft right after molting and he was probably sucked way down in his shell to protect himself.

 

[jasonp87]

Some could be molting, though i have never seem hermits molt before. More likely it is a competition between the hermits over larger shells. If there are not any shells to move into when they outgrow their current ones they will attack other hermits and even your snails for new homes. I had blue leg hermits in a 75 that would hunt and kill large mexican turbo snails for their shells. Now I just keep lots of extra sizes available for them. If you have snails or hermits die just keep the shells in the tank. Eventually you will build up lots of choices for your hermits. Many times you can also go to the store you purchased them from and request news shells since the old ones were outgrown. A lot of places will give them to you for free.