Mag is a little lower with the IO mix, at first I bough a bottle of Mag to dose with, but after about 4 months of keeping up with the Mag I stopped playing with it. its been about 4 years since I stopped playing with the Mag, the Mag dose run on the "low" side, but I have seen no ill effects, pH, Alk, Ca and such are all running close to natural levels, and I have no complaints.