So I was testing my Mg this week and was quite shocked to see that it was at 950ppm. The tank is a very new setup but cycled (2-3mos old). I had only done a couple small water changes but since I dont have any coraline or much in the tank other than dry rock and live sand, I wouldnt expect such a drop in Mg. Especially since Instant Ocean has 1264ppm. Since then, I started boosting it up w/Gary's DIY formula and it seems to be bouncing back as expected.
Anyone have any idea what could be dropping it - or are my expectations off base w/a cycled tank and only a couple small water chgs in 2 months?