I have a yellow, purple and blue hippo tang. All have been fine together. yellow was in first, purple second, and blue hippo third. I have read alot of forums on here about aggressive purples, but mine is fine. The LFS where I bought it had it for a very long time, and it was in with several varieties of tangs. I bought it when they clearanced it. I knew from seeing it frequently that it didn't seem aggressive. I'm sure its different for everyone and as well, the size of your tank may make a big difference as well.