I've noticed after my water change,my crab was moving around quite a bit.Then,after a few days,my wife called me and said that the crab was dead. a few days later,when i came back from work,I took it out and before i chucked him,i noticed that his "gills" were slightly moving.I put him back in the water.He still has not moved at all.Could it be that he was starting to molt and got stuck in the process?