He's been in QT for 6 weeks. I initially treated with hyposalinity (1.009) and reduced doses of formalin / malachite green. But I discontinued the meds when the spots cleared. I bought a bottle of cupramine just in case, but it doesn't appear to be necessary, since I haven't seen any symptoms for at least three weeks. I did add the Zoe to his food as recommended, and that seemed to make a huge difference in his color. So that will be a staple in the diet from now on. I have also given him part of a seaweed sheet every day the whole time. He seems to enjoy that as well.
I have a new (to me) 90 gallon set up all cycled and waiting for him. I plan to transfer him over pretty soon. When the original 75 setup is through the fallow period, I get to start thinking about how to set up a second system!