I started my solon fairy wrasse on copper a few days ago. Due to a calculation error, I added maybe a bit too much on the second day and he started acting wonky. I did a quick 20-25% water change because he was swimming near the top and acting like he couldn't get enough air, despite the air stone, powerhead, and hob filter. I didn't add anything the next day. In fact, I have added zero copper to the system in two and a half days, and the levels continue to creep up a little bit. I am using the Hanna checker, the reagents aren't expired, I ran the calibrators, I'm thoroughly rinsing the cuvettes (tap first, then RODI rinses) and drying them between uses....what's up with the copper levels rising? In the QT I have pvc fittings, a plastic plant, a small satchet of ceramic media (I keep a bunch of these in my sump for insta-cycling a newly set up tank), and a small dish of sand in case he wanted to bury himself. You'd think the copper levels would drop as it's absorbed by the media and sand. I mean, it's not jumping hugely, but it is creeping north and it's got me befuddled. What are your thoughts? Should I wait another few days without adding anything and keep testing to see what happens? Add a very small amount to see if the change is more significant?