Originally Posted by MrBishop
Im not sure what its called but heres a few pics for ya
That is a Mimic Tang, aka Chocolate Tang, Acanthurus pyroferus. As Juveniles they will mimic the color pattern of Centropyge Angelfish, in your case the Lemon Peel Angel, Centroypge flavissimus. As adults, they are a deep brown/purple color, as you might expect from their other common name of Chocolate Tang.
This is a reasonably easy fish to care for in the aquarium, although it is an Acanthurus Tang and you will have some serious growth issues to deal with. When kept in smaller tank sizes, such as your tank, their aggression is much more of a problem and your Tang will probably make life difficult for future fish additions. I would play it safe and not add any other open water species, sticking only with rock dwellers from this point forward.
Also, be certain to feed algae sheets daily. You will not keep this fish successfully simply feeding flake and frozen foods alone. Their metabolism is crazy high and they require an abundance of algae to remain fat and healthy. I personally use the San Francisco Bay brand of algae sheets, which you can order online in bulk.