HELP!!

Question
i got my very first hermit crab a few weeks ago, me and my brother and sister won him at the fair. when we first brought him home we weren't very prepared for him and so i just quickly put together one of my old fish tanks with gravel at the bottom and a few shell as decorations and to use as food and water dishes. he seemed to like it for the first couple of days and we would play with him and he would always crawl around a lot and was very active, then he started becoming very "lazy". and he wouldn't move around or really do anything and he would just sit in the corner of the tank. so i thought that changing the gravel to sand would help and while i was changing it i noticed he had lost a leg and i didn't really think much of it. also i have never seen him dig underground and he is always on the top of the sand. then today my friend came over and she went to pick him up and his big pincher fell out of his shell. I'm wondering why this is happening and why he never digs. my sister thinks he might be dead. what should i do ?

Answer
It sounds like your humidity is too low. Losing limbs is a sign of stress. Are you handling him a lot? You need to give him time to adjust. Does he have a place to hide? Do you have fresh and ocean style salt water available in pools deep enough to climb into? These things will help considerably.