OK, I can see it killing off the LR, but why the copper? I thought you should never use copper to treat marine fish. It seems that there would not be a way to introduce copper into the QT or the LR.
If you don't have LR in the tank, then how are you able to maintain the correct water levels in a QT? Do you just put in the fish into the water and then do 20 or 50% water changes everyday? I am not trying to be a smart ass here... I really want to know, I know I will come across this some time in the future.
Tim