CTs can play nice, even for years, then go postal. You can never let your guard down with these fish. I recently had a med CT kill a Goldbar Wrasse, a fast and aggressive fish, before I could do anything about it. Scary, the CT was just staring at the wrasse and suddenly was chewing at the wrasses gills. Several years ago, I had one (about 8") kill or maim almost every tank occupant over a week-end. All of this tanks fish were together for at least 3 years; victims included a Niger Trigger, porcupine puffer, pinkface wrasse and a couple others. Many authors recommend a species tank for these fish and I finally agree with them.