I am really struggling in the same boat... AF reef salt, dosing components 123 minus 3 because of mag issue... On a doser. Red sea test kit reads 1620 to 1640 ish. Did a 20 percent water change today with Instant Ocean Salt (not reef) and still have mag at 1600... Really looking for some advice. Cant get my magnesium down
Truthfully I don't try to lower my mag anymore. I focus on Alk and Calc because they're what my tank uses the most. Mag is still over 1500. Having no issues with live stock.
Considering trying the HW salt instead of AF reef salt on my next salt order.