[leebca]

WELCOME TO REEF SANCTUARY!

Mal nutrition is one such source of a 'skin' problem amongst Tangs, but this can lead to bacterial infections. Make sure you are feeding the fish properly:
Feeding Marine Fish and Marine Fish Nutrition

Move the fish to a hospital tank and treat with an antibiotic. I recommend Maracyn Two for Saltwater fishes.

Skin bacteria can quickly kill a marine fish if not arrested. In the case of Tangs that have little mucous coating to begin with, the captive fish can be overcome by bacteria very quickly.

Next, find out where excess bacteria may be coming from. Are you keeping up with maintenance? Is your tank free of detritus? Do you have and use a skimmer? Are you keeping the skimmer clean and operating properly? Is the skimmer sized properly? Are you using carbon? Eliminate excess organics and waste build up.

While doing the above, review the foods and, like Terry mentioned, start the fish on proper foods with vitamin and fat supplements.

After the fish returns to normal, return it to the display.