Thank you Beth,
I was reading an old article on Zebrasom Tangs and reef aquariums by Albert J. Thiel, Dec. 1996. These Tangs he said are very susceptible to disease, and I know that right. He suggest to treat the tank with C a couple of times a year, at the rate of 5 ppm of C for about 14 days. He said your fish will have more color, be livelier and will not suffer from disease and parasitic attacks. He also said Vitamin C is an excellent way to prevent this and will cure diseases that are ususally hard to cure. I'm looking for any way to keep my fish happy. Guess I can stop checking Vitamin C out!