White Cheek tang??

ive got one of these and a yellow tang, they do occasionally try to scalpel eachother but they havent really went for it, on the whole, lovely fish, he's the biggest one in my tank so he eats like a pig.

 

Thanks Horkn the pic really doesnt give justice to the thin blue outline he has but my camera sucks. As far as aggressiveness IMO they are a medium aggressive fish. The WC def lets any new additions know who the boss is but after the initial day or so everything is relatively peaceful.