In this hobby we're dealing with nature, as well as science. I've had a FOWLER for over 3 years now. All my fish are over 2 years old. Granted I *cycled* quite a few in the early months. But I didn't want to make any more victims than necessary. Now, that I'm confident I can step up....my fish destroy any invert I add...my blenny bites the heads off of snails and leaves them totally bored once they are demobilized. (I'd feel better is she would actually eat them.) My tang snacked on my feather duster for days. I'm not sure it will make it. My starfish strangles my shrimp.....And I overfeed to reduce aggressive behavior. I think I need another tank for "pretty things."
Your tang would be a great fish to have in my tank. It is so hard to remove Star polyps once it attach to rock. It just continue to kill my SPS. I just have to tank the rock and any SPS on it out.
In addition to naesco's question of How much do you feed? I would also ask What do you feed?
Purple tangs like to pick all day long. Mine gets a section of either Seaweed Selects or nori to work on every day. In addition, mine gets blanched broccohli on occassion. This is in addition to the regular tank feedings.