Ah, nice! He looks something like my Pilumnus sayiis, Spine-backed Hairy Crab. Big, fast, strong suckers, very cool for a Sin Bin. He may eat your hermit. He'll definitely eat snails. Might leave stony corals alone, if he's the same species? Mine hasn't touched the small hitchhiker stony corals in with him.
Teach him to take food from tongs, then you can impress visitors with him when he gets big.
Teach him to take food from tongs, then you can impress visitors with him when he gets big.