I actually have no clue what happened but this morning I saw that my hermit crab had died and fell out of the shell so I naturally took it out and disposed it. However, now I’ve come back and see that somehow the shell has another crab in it ( the one that I thought died was the only one I had so another one couldn’t have just climbed in it’s shell ) so what happened to it ? Did it molt ?
Next time leave the molt for them- if what I’ve read is accurate, supposedly they eat it, and it replenishes their lost minerals and helps their new exoskeleton harden faster 

