Stable Chem except Mag dropping, why?

[NC Jim]

For the last 3 months I have been having stable parameters except for Magnesium. It seem to keep dropping. I have been adding mag to bump it slowly back to 1350 but over the course of a week or two it drops back to 1230-1250. Does anyone know why this might be? The rest of the parameters are as follows
PH 8.3-8.6
ALK 7.8
Calcium 400-420
Salinity 1.025

Any information would be appreciated, thanks

 

[14 foot reef]

Randy HF replied to a thread yesterday that he seemed to think it would be more of a test kit error than actual MAG dropping that fast without Ca and Alk dropping much more.

 

[NC Jim]

Hmm interesting. I would tend to think that would be probable except that the mag drops each week as I test and not random each test. I did 3 in a row a few weeks ago and got almost the same value all 3 tests. I use salifert test kit.

 

[Randy Holmes-Farley]

If you are not adding lots and lots of calcium and alkalinity, then dropping magnesium is either test error or salinity dropping.

There is no sink for magnesium that does not consume about 10x as much calcium as magnesium.

 

[NC Jim]

Salinity is very stable so it has to be kit error, thanks Randy.

 

[nereefpat]

Yes, a drop of 100 ppm Mg would be about 1000 ppm of Ca or about 140 dKH!