major elements daily consumption?

therealman1 · Jun 4, 2019

I just went 4 days without adding elements to find my average daily consumption of alk, cal, and mag. I was just curious if this seems correct.
Alk: .95 DkH
Cal: 12.2 ppm
Mag: 40.3 ppm

This is for a mixed reef 32 biocube with around 30 peices of coral. ranging from zoas to one acro frag.
Follow up questions would be that since I am hand dosing when would be the best time to dose these elements? and when should I test my Alk daily?

Ron Reefman · Jun 5, 2019

OK, every tank is different, and yours is no exception.

To me your alk & Ca seem very normal. Your Mg seems way out of line. Are you saying your Mg goes from (example:) 1300 to 1220 in just 2 days?

I have a 40g cube stuffed full of zoas with a lot of Rock Flower Anemones and only a few lps and sps corals. I also have a 40g sump/refugium full of a mix of macro algae. My alk goes down 0.5 to 0.9 dKH per day. My Ca goes down about 10.0 ppm per day. But my Mg hardly goes down at all, maybe 10 ppm per week or 10 days.

IMHO, I don't think the time of day that you dose really makes any difference. As for testing, doing it roughly the same time every day is more important. And being careful to do it the same way every time is even more important. Our test kits are not all that accurate but by doing it the same way (carefully) every time, you at least get trends that are more reliable.

madweazl · Jun 5, 2019

therealman1 said:
I just went 4 days without adding elements to find my average daily consumption of alk, cal, and mag. I was just curious if this seems correct.
Alk: .95 DkH
Cal: 12.2 ppm
Mag: 40.3 ppm

This is for a mixed reef 32 biocube with around 30 peices of coral. ranging from zoas to one acro frag.
Follow up questions would be that since I am hand dosing when would be the best time to dose these elements? and when should I test my Alk daily?

Typically, a reduction of 2.8 dKh corresponds to a drop in calcium of about 18-20ppm and 0-2ppm magnesium. Based on this, I suspect testing error; most magnesium kits aren't very precise so it's easy to get a larger delta that you expect (a drop roughly equals to 15ppm for Salifert).