The hippo tang was never in my 75g DT, he was in a 29g I use for a QT, then when he showed signs of ich I moved him to a medication tank. I went with the copper method because ive had success with the method before. The tang also was still pretty strong and i knew it would survive the stress of the move. As for how long copper treatment lasts, the directions on the bottle say to continue use 3 days after the last sign of disease. It took about 2 days for the spots to disappear and I continued the treatment an extra day just to be sure.
As for the popeye, I changed probably around 50% of the tank water today, and will continue changing 50% for the next few days. Hopefully that will clear up any water quality issues, and will see if there is any improvement.
Sadly it has lost some of his appetite, I hope it hasnt taken a turn for the worst.