That is a negative! ;-)
Poly Filter is a color-changing adsorbant resin in the form of a sponge/filter pad made by Poly Bio Marine.
Anyway, as it sorbs chemicals it changes color based on the chemical - blue for copper, for example. I would link you but it's not so easy right now. Google "poly filter" and you'll find tons of info on them - been around for decades and is a very inexpensive, reliable solution. I know many people who run them on established tanks as a standard part of their filter regime. (Not nessary for most people, but good option if you need it.)
Even if your Cu test comes up negative, I would highly recommend you run one of these pads as it may just be something bad other than copper in your tank.
Good luck and don't give up hope!
-Matt
P.S. I did read the thread and I wouldn't point you to regular filter floss as a solution after all that. ;-)