Magnesium cosumption

[alexytman]

I'm currently restocking my tank after a crash over half a year ago. During that time I added a few leathers and other softies. Then I recently added LPS again. Some euphyllias. Galaxea. Acanthastrea. Lobo and scolys.

Then I noticed a trend with my big three.

Obviously my kh and Cal would go up alot, or so I thought

My Cal only dropped about 40 from 440 to 400ish from my usual dosing plan

Kh dropped a whopping 0.5 from 8.9 to 8.4

Mg though, dropped from 1350, which I was planning to decrease in the future to under 1200.
This all happened in a few months period.

 

[Larry L]

I wouldn't expect calcium and alk to change much at all - they get consumed (mostly) when corals are laying down calcium carbonate for their skeletons. Softies build very little, and unless your LPS are growing like crazy, you won't see them using much either. I never used to dose my old softie/LPS tank, occasional water changes were plenty for maintaining calcium and alk levels.

 

[chipmunkofdoom2]

Is your question about magnesium consumption specifically? There's effectively no mechanism by which magnesium can drop by 150 ppm when alkalinity drops by only 0.5 dKh. Not without water changes with a low magnesium salt mix. This is likely testing error.