Okay, so I have two hermit crabs and my younger sisters each have a hermit crab, and I take care of all of them. Now I noticed the biggest crab, has lost it's largest pincer. I'm not sure what's happened but It's large pincer is on the floor of the critter keeper (I'm cleaning out the 10 gallon at the moment). What should I do? Also, what would you guys suggest for substrate? I've been using sand, but I was wondering if you guys suggested anything different.