I use to put my hand in the tank all the time with no problems. A few weeks ago I put in 2 large zoo rocks with over 200 heads. I had my hand in the tank a few hours afterwards and the little fricker bit me. Nothing hard and no blood but caught me off guard. Now everytime I'm cleaning or doing anything he's always gettin me. He doesn't host the zoos. I guess he just really likes them. Is this normal?