Confusing Ca and Mg test results

[PDR]

It's me again and I'm still confused . This time it's Alk.

I am still not dosing anything to the tank, just trying to get a good base line for consumption. I'm mainly just paying attention to alk but I go ahead and do the calcium test while I have everything out.

Here is the timeline:
- 5/29 - 20% water change with IO
- 5/30 - added some mushrooms, 2 small lps frags (torch and blasto) and a 2" birdsnest frag.
- 5/31 - alk 11.2, ca 470
- 6/3 - alk 10.2, ca 460
- 6/7 - alk 9.6, ca 450
- 6/13 - alk 9.6, ca 450

So according to my tests I went almost a full week with zero alk or ca consumption. I can confirm I have done the tests the exact same way every time and even did them each several times today just to make sure I didn't screw something up.

No water has been changed, nothing has been dosed and salinity is still at 1.025.

Any help understanding this would be greatly appreciated!

Thanks!

 

[Randy Holmes-Farley]

I just think you have pretty low demand. The demand declines as the alkalinity declines and the drop from 11 to 9.6 dKH may have been mostly abiotic precipitation, which is not abnormal.

Just check to be sure everything else is ok. Enough N and P for corals, light, flow, maybe trace elements, etc.

 

[PDR]

I just think you have pretty low demand. The demand declines as the alkalinity declines and the drop from 11 to 9.6 dKH may have been mostly abiotic precipitation, which is not abnormal.

Just check to be sure everything else is ok. Enough N and P for corals, light, flow, maybe trace elements, etc.

I thought the amount of alk "used" over those first few days did seem high for my tank, but I did expect some usage over a week's time. I never considered it could be precipitation over a few days like that.

Thanks again Randy!