While we're on this topic, Bulk Reef Supply's recipe (which I made and use), and (the other) Randy's articles which Chris linked both mention more or less dumping the whole Magnesium portion all at once or nearly all at once when the 1g of each 2-part is gone. That seems like a terrible idea, especially for smaller tanks... there's just no way. Anybody have helpful info on dosing the Mag portion of these recipes on a more regular basis... '3-part dosing'?
I don't gots a Mag test kit yet. Arg. Darn you Salifert.