I appreciate the reply, I should have clarified, in my personal QT protocol copper is only to treat ich/velvet, I treat separately for flukes (prazi) and other ailments. I'm curious where you see the possibility of failure with that protocol, or if you have personal experience with it failing. I don't recall the exact study, but remember reading that the longest ich trophonts had been recorded feeding on fish was 9 days, and I believe that was at cooler than reef tank temps. As long as copper is kept at therapeutic levels, once all trophonts have fallen off the fish should be ich free, no? After the copper I catch the fish with a strainer and transfer to a clean observation tank
I guess I am more cautious because I have dealt with a number of sensitive species, things like leopard wrasses, certain centropyge angels etc. that can seem to turn quickly in quarantine, and for those species (even with chelated copper) minimizing their exposure time seems to increase chances of success IME.