I've had a black one for a year and a half in my 120g with the same sand (miniflakes). You want as much sand area as possible so it gets enough to eat. Mine takes in sand all day long. I've noticed it doesn't seem to feed where I have a few patches of cyano. Mine was 6 inches when I got it and is well over 12 inches when stretched out now. Don't think I'd have a sand bed without one. If you get one keep a close eye on it for the first few days to make sure it makes the transition to your tank ok. Not sure how toxic they are if they die, but I don't worry about it. Mine went right to work eating sand and seems to be thriving.