it’s on both my clownfish all of a sudden. I recently moved my tank to the other side of the room had these guys for 3 months. They have been swimming and eating fine.
No new fish recently but I had a dottyback that passed like a week ago. Had white spots on her but they were big spots and I was told it wasn’t ich by my LFS.
I had this and received advice from a lfs to add this cooper medication to my tank which definitely cured the rich (which is what yours looks like) but was not advice so well like you have above about doing this treatment in a hospital tank and put it straight in my tank.. this in turn changed my tank to a 'cooper tank's which meant I could never have invertebrate or corals.. in the end after carbon and mass water changes after nearly a year of trying to reverse this my tank would never hold any other life bar fish and I had to get a new one! So definitely hospital tank and just a heads up this is a quick killer in my experience so sooner the better.