Cupramine unless the fish you QT is scaleless in which your current stock shows you should be ok but you may want to check with your clownfish as I've read that they can be sensitive to copper. With Cupramine you start off with a lower dose and ramp up to therapeutic levels so I would get started first and use the ramp up time to feed and let the fish settle. That Powder Blue is a nice fish but is an ich time bomb. If it was exposed to ich and looks like you said it was, then it's a matter of time when the ich will manifest on the PBT.