What are you talking about there are plenty of mag test that are acceptable for results, salifert works well and Hanna just released a checker but im not sure of that one yet also plenty of other brands . Yes test magnesium it is important h.sThere aren't many magnesium testers out there and those that are in my opinion have too many steps and too complex especially for your size tank. Unless you have a **** load of coral than I wouldn't worry about it