Hello all, I am new here to these forums. I am also new to aquarium keeping. I recently got a live rock from friend, and I find crab in it last night. It only emerge in darkness, so I cannot get a picture. But after searching, I think he is red mithrax crab. I also discover he is dangerous to my tank, but I cannot catch him. I have try using soda bottle with bait, but he does not take it. Does anyone else have ideas? Thanks you!