I can't tell you why it got those white spots, they must have been superficial to have gone away in a day like that. I think you could back the copper off in a day or two. I have a general rule; if a fish shows symptoms of an issue, whether I cure it or it goes away on its own, I always wait 30 days before moving it into a display tank with high value fish. So - no fish gets moved out of the QT within 30 days of the last time it showed symptoms. If your quarantine tank isn't stable and you are fighting water quality issues, you might need to make a judgement call and move it at 14 days. I just wouldn't do any less since we din't know what caused the spots to begin with.I had a purple tang in quarantine with copper power at 2.5ppm for 28 days. He started to look very bad (in the photo attached) so I setup a brand new, clean tank with saltwater at 2.5ppm copper power as well. I moved him over last night, so today is technically day 29 in therapeutic levels of copper. Today, he looks 100% healthy again, any ideas what happened to him? & Will he be okay to add into my display tomorrow?
