When to put sick fish back in main tank?

I have a black moor that has fungus. I was given some medicine and was told by the lady at the pet store to put 1/2 tablet in the 2 gallon quarantine tank a day for 4 days. This was last week Thursday-Saturday. He has cleared up a lot, but he still has some spots. He's still in the treated water in the quarantine tank. Should I do a 25% water change for a few days? I really don't want to keep him stuck in the little tank but I really don't want my other goldies in my 60 gallon tank to get infected. Just wondering what my next step is...