Ok, some of you know my story, some don't...I bought live rock....Sunrise Dottyback, hitches a ride. First fish in tank, ACCIDENTALLY, not my choice. Pleasant to watch, but classified as Semi-aggressive, I decided to keep him, and add tank mates according to his temperment, and certain compatibilty charts. Add Percula Clownfish....no drama. Add Yellow Clown Goby....no drama. Add Green Clown Goby....MAJOR TROUBLE. He not only chases him when he's in sight, but seeks him out after swimming a lap around the tank just to hit or nip at him again...even if he is hiding on the underside of a rock.