magnesium uptake in sps tank

[Willito]

IME, once your tank is stable and assuming all 3 levels are near NSW, magnesium will deplete at a rate of 1:2 in reference to CA and ALK. In my tank, the magnesium is the most stable element of the three, it's solid. As for the Zeo Mag, I think this product is junk unless you have a CA reactor and willing to measure it constantly. Better off using mag in bulk chem for accuracy and economically.