Well here's my situation - I bought a purple tang forgetting about the whole tang aggression issue. My parents have been stocking a 210 and have been throwing in tangs willy nilly with no problems so it just slipped my mind. I already have a yellow tang in the tank. I threw in the purple tang 3 days ago and the yellow(being slightly bigger and having territory already) was harassing him like crazy. So on a recommendation I caught the purple and put him in a breeder box in the bottom center of the aquarium so that the yellow could "get used to him." The aggression towards the tang in the box had slowed down over the couple of days that I had him in there, so I figured I'd try releasing him, but it seems like now the yellow is just as aggressive as before. I would just take the yellow and put him in the sump for a while but he's a lot more difficult to catch. So really I'm clueless as to what to do besides getting rid of one of them at this point, but I was hoping maybe I could pick up another few ideas on here.