BTAs are all different; sometimes they move around a lot and can't seem to find a spot they like and others settle in right away. They eventually pick a spot that works for them. Carpets can get big, and your tank would be about the smallest I'd go for a carpet and probably wouldn't do any corals in the tank. They're not exactly poisonous...if you happen to get stung by one, you'd probably get some pretty nasty whelts and/or blisters and if it were to sting a coral, that wouldn't be pretty either. So basically, just don't tough them. Clowns love them though