Used to use NSW for water change, recently change to salt mix. Last major change was about 450L using 1 bag of ME and 1 bag of left over Coral Life. (that about a 50% water change, about 1mth ago) Yesterday changed about 60L, using TM salt.
My mg levels was around 1300 b4, maintained by CR using ARM media and Grotech mg stones. But the SG used to be at 1.025.
Not really sure why the sudden drop. I have also been dosing 150ml of KentMarine M Tech almost every other day, for the past 2 wks.
As for trying to raise it too fast, yes, I did that too and most of my zoas bleached. Raised from 1150 to 1300. But the mg levels dropped again in about 2 days, back to 1100+. Can't remember the exact no...