I don't like Tangs for frag tanks. Actually, I like the IDEA of Tangs in frag tanks, but they always end up agitating me more than anything. Not sure what you're planning to grow, but tangs are notorious for stealing any food I spot feed chalices/acans/LPS. Even if I wait for lights out, they wake up and get aggressive for the food source.
I know they are amazing for picking at algae, but I if you plan on spot feeding don't bother.