Just to clarify, the 5 teaspoons was not straight cupramine.
It was 5 teaspoons or so of saltwater that had cupramine in it. So the 5 teaspoons had a concentration of .5 ppm. Really a tiny amount of copper overall for 260 gallons, no?
Or did that tiny amount ruin all of my rock and sand? API copper test currently showing 0 ppm for whole system but the API kit seems pretty imprecise in general