I bought the kit that tests for Mg, Alk, and Borate, well i ahve only used it once to test Mg and well....i pretty much hate it. It's sort of like Salifert, which i really liked but it only tests up to 1250ppm then you have to re-load teh syringe and keep adding drops till the sample turns blue. Long story short, i guess if add a whole syringe full of the solution and it's not blue im "in good levels" if it turns blue before i run out of solution in the syringe, i "need to dose". Uhg.....for $30 i was hoping for a better kit. Should have waited for the Elos.