The copper levels I'm getting are quite low, .1 to .2 ppm but apparently still toxic to inverts and corals. I have been using cuprasorb and poly filter and still doesn't seem to make a dent, not sure if the Cuprasorb is exhausted from their website it says it will go until it gets to be a deep blue or black but I am nowhere near that, still at light blue after several weeks . The poly filter does change from white to dark blue in a couple weeks. As for the Hanna copper test I'm trying the high range and there is an extreme error level so I'm experimenting with multiple readings and take an average. I should have got the low range kit but it seems hard to get and very expensive when purchased from Hanna directly. I'm sure I'm getting leeching from gravel and reef rocks and there does not seem to be any short-term fix for this. Seachem is not being very helpful.