I had one that was a complete terror of the tank. It wasn't always that way, when I first got him he was pretty calm and got along with everyone. As he got bigger he got much worse. I think I've read that they become more aggressive as they grow larger. It got to the point where it wouldn't leave anything alone and was impacting the quality of the other inhabitants feedings and everyday lives. I was finally able to get him in a homemade fish trap (good luck with a net!). I was very sorry to have to part with him, they are one of the most beautiful fish, IMO, but I would never add another one.