There are many different ions in seawater, and as reef aquarists we generally only test for a small number of these. Calcium, magnesium, “alkalinity”, nitrate, phosphate, and ammonia, for example, are relatively easy for hobbyists to test at home using kits. Other ions, however, are more difficult to evaluate because they are present at such low concentrations or are otherwise difficult to detect. Even if there was a suitable kit for every ion in seawater,...
