My cousin, who is an EXPERT aquarist regardless of the responses I'm about to get, has a purple tang, a yellow tang, and a blue hippo tang in a 60 gallon cube in his office and has no aggression issues. He introduced the tangs all at once. I'm not saying this is always advisable (so the tang police don't arrest me) but I'm using this point to illustrate the fact that these tangs can get along even in a fairly limited setting. Your tank is twice as big as that. Not that I'm telling you to do it, just that some of the tank sizes for tangs on this board are a little silly in my opinion, and the opinion of my cousin who again is an expert. His tank is maybe the most beautiful tank I've ever seen and is a true masterpiece as far as equipment, attention to detail, and keeping parameters in order go.