I have 2 QT tanks with copper, and cleaner shrimps in my display, and I know that removing all of the fish for 4-6 weeks will cure the ich, what my question was trying to ask was this, I have QT'd all of my fish with copper, I only buy my fish from a LFS that keeps all of their fish in copper, so how the ich got in my tank in the first place, I don't know, but if it got in there once, would it be waiting again when my fish get out of QT?[/QUOTE
As said before, the ick cycle is very hard to break without letting the tank go completely fallow for at least 6-8 weeks. They are like roaches, hard to find and kill. The different stages live in the sand, rock, coral etc until a fish is compromised somehow. Then bam, it hits.
Are you allowing your fish time to adjust (in the qt) after copper treatment is over, with the main tank exact perameters before putting them in? I hyposalinity everything that swims before going in the main tank. You can not rush this. 3-4wks hypo, then slowly, key word slowly bring the qt up to the main tank. If the main tank has no possible chance of ick you can use the water from there to do your water changes. I then leave the fish in qt another 2 weeks. Seems extreme, but it has saved the day many times. I have had fish do absolutely fine in qt, then days before they are to go into the main tank, they get something. If I had to catch them in my 125 reef tank with plenty of rock and coral I would go out of my mind. Don't rush the process.