How thoroughly do I need to wash my arms and hands after working with QT tank containing 2.5ppm chelated copper. I don’t want to accidentally introduce copper into my sump in a separate fish room, nor do I want to contaminate the display with a coppery arm. Further, if a bucket, or heater has been used with copper, will it forever be a copper only device. finally, what about using the same refractometer with the copper bin and the display tank water. I have used a separate pipette to grab the copper-dosed water. I rinse the refractometer with RO/DI from a spray bottle. what else am I missing in the multitude of copper cross-contamination issues. I worry about the things I can’t see, including the soap residue on my arms. My advance apologies if I am somewhat paranoid!