So, (sorry saying this all over again from other threads). I took all my fish out of my tank December 2. I have two QT tanks. I emptied one and added 4 fish back to the DT 11 days ago. In my other QT tank, I made the mistake of adding new fish, so I re-treated with copper (third time since August with a few of the fish). I don't want to keep them in copper much longer. Its been three weeks since the copper levels were at the correct levels. So far, no sign of anything. The last fish was added about 4-5 weeks ago.