Your Vlamingi Tang [pic very blurr leh ....
There's what i get from the web
Althouth this species has a wide range in nature it is not common in the aquarium trade due to its inhabiting deep water. Very durable in captivity, hardier than for example, the common "Naso Tang" Naso lituratus Shown is a very large, fully developed male specimen
http://www.themarinecenter.com/tangvlamingi.htm