Thanks for detailed responses everyone. I bought the Copper unit because I was going to prophylactically treat fish going forward, but I'm having second thoughts about it. In any case, I have it if I need it and that's a good thing. I am planning on buying the alkalinity checker next.
One thing I was told a while ago, that I was suspicious of but also kind of makes sense, is that the API Phosphate kit is fine for the average hobbyist, especially since I was only keeping fish at the time. The theory was that you really just need to that it either is zero, or it isn't.
