How bad is 0.01 PPM Copper?

[BZOFIQ]

I would not overly worry about 0.01 ppm (10 ppb) copper. FWIW, I had 10-15 ppb copper in my aquarium water the first time I measured it myself by ICP many years ago, and saw no apparent issues in the tank.

That's great to hear. Triton shows it in RED because they expect absolute 0 as acceptable. I'm still going to remove it in order to have a better/safer transfer to a system that will host more sensitive corals down the line.