I tried Dr. G's for a Sailfin with ich and had to stop feeding it because after he looked as if he was being poisoned. His color changed to a pale white and he was very getting lethargic. The Tang had ich for several weeks but could not shake it buy himself. He was always active and still ate like a pig. I bought Dr. G's antiprasitic and feed him according to directions on the package. An hour or so after eating he would look bad but, then seem better by the end of the day or morning. After several days the ich was still their and I finally discovered the correlation between him eating the medicated food and looking so bad afterwards. I stopped treatment and removed the fish and was successful in curing the ich with copper.
After all that work the Tang was fine and reintroduced into the tank, all was great for a while until he decided to go on a lps eating spree and had to be returned to the store. Sucks that I put so much work into a fish only to have to get rid of him.