Hi
Another thing you might to take note is that after the copper treatment pharse is done, its good to slowing introduce your main tank water to your QT.
This is to allow your fish to get used to a "copper free" environment and slowly built its immune system again. Cos even though the fish is free of ich that doesnt mean its immune system is strong enough to fight it off if it is introduced into the main tank where ich may be present.
This was taught to me by Herny of ML.
You may want to ask him if you do not understand what i have just type
Cheers