[gmat]

Won't a very caustic mixture attack the copper itself ? I heard that bleach would eventually do more harm than good.
On my next refill i'll try a commercial product made by alphacool - it's a special additive made for WCing. I'll tell in 6 months if it's snake oil or not :P
(see why we're running circles - unless you can run multiple test loops for that purpose only it will take years until we find an acceptable solution)