Yes. I've even had clownfish sensitive to copper, and they are very hardy fish.
I've used CP to QT in the past but, as stated, is hard to measure. Any suggestions to measure, or a reputable source?
Never heard of the TT method until now. Seeing as I have 2 QT tanks it wouldn't be hard. What do you use to clean after draining?
I have no problem using copper with large angels, but every cent. i've QT'ed with copper has shown sensitivity to it (potters, coral beauty, flame, halfblack, etc). All "Bread and Butter" fish. I'm down to using MB, which is more of a preventative than anything, and dyes your tank.
I always dose copper over 4 days instead of 2, so thats not the problem...
So many methods to consider, thanks for the responses everyone...