We got 2. One of ours died. Well, I didn't think he was dead, I thought he was shedding but DH did so he went. We've only got 1 atm, DD seems to have lost interest. They are incredibly cute though.

Our tank has shell grit in the bottom. The pet shop lady said it was better for them than sand or sawdust because it's what they live in in the wild. Who knows. She could just have been wanting us to spend more $.