Magnesium being drained?

[Pricey95]

So I've got my tank set up and been established for a while now. The live rock I have was From a friend that was been running for about 7 years.

The magnesium drops in two days from 1350 to 1250. Without fail its always 100 points for every 48hr. The calcium and kh isn't dropping at all. I did infact put in some dry rock a couple weeks ago for more structure.

My understanding the mag can't drop if kh isn't being consumed?

Parameters:
Ph 8.2
Mag 1250
Calcium 430
Kh 9.3
Nitrate 8
Phosphate 0.5
Salinity 1.025

Got 3 torches and a big hammer and then a few candy's and softies. The rock has tons of coralline algea

 

[Randy Holmes-Farley]

The magnesium drops in two days from 1350 to 1250. Without fail its always 100 points for every 48hr.

That can only be test error or a significant salinity drop.

Real magnesium consumption cannot be more than about 2 ppm a day, and that is only when alk and calcium demand is very high.