Learned the hard way that Blue Stripe Butterflyfish (Chaetodon fremblii ) will not tolerate cuprmine. I am very strict on my QT regiment and usually do TTM. No fish goes in DT without 6 to 8 weeks of QT. Somehow I got ich in my tank. The only thing I can think of is when hosting local fish club meeting at my house someone floated a few bags in my sump without my knowledge until it was too late. And one of these bags was leaking. Well two weeks later ich started showing up in my tank. They did well for about 6 or 8 months then it started getting worse so I decided to take all 15 fish out and put in QT for treatment and go fallow for 3 months. Fish are divided up into 3 different QT tanks. With this many fish I decided to use copper treatment. I am ramping up copper over 6 days adding 1/2 dose cuprmine every other day. Well yesterday on dose 2 my Blue Stripe Butterfly, that I've had for 18 months , started laying on it's side and showing signs of copper poisoning. I transfers this fish to a new tank with fresh salt water but it was too late. My other fish are all doing well with copper treatment. So add this fish to the list of no copper treatment.