What are the effects of adding copper to a fowlr tank. I know it will kill the rock, but will this kill all the bacteria and hence the fishes? I have had several fish in hypo for about 7 weeks now and the fowlr running fallow. Yesterday I decided to start adding the fish back to the aquarium one or pairs at a time. I added my koran and he seemed fine in the qt tank, but once I got him under all the lights in the display, I don't know. He didn't have anyhthing on his fins, but his body looked as if there was maybe 1 or 2 spots. Possibly. It could've been the coloration stress as he looks great today. But I am concerned. I don't want to add any of the other fish because of this, but if I don't I will have trouble adding them ( couple angels) later. Im thinking If I have to I'll add copper....will this kill the bio in the tank? anyone done this? thanks.