No dosing but calcium went up alkalinity down

[nkyreef]

So I stopped dosing BRS 2 part to try and nail down a more accurate dose via BRS dosing pumps. 12/3 (right after a water change) alk measured 7.8 and calcium was 410. Today I measured 5.8 and 425. What in the world is going on? I use just straight ro/di water for top off nothing else went into the tank over these 4 days.

 

[Breadman03]

I suspect that your consumption is low enough that it's just within the noise/margin of error in the test kits. Assuming your alk measurement was perfect, you could assume that your tank consumed about 14 ppm of calcium per the ratio that Randy posted here. It seems to me that 35 ppm (14 plus the difference between your tests) could easily be within a reasonable margin of error.

Hi Pete, I edited the quote in your post to put the 3 on the line with the CaCO so it showed CaCO3 correctly.

Calcium consumption is about 18-20 ppm for each 1 meq/L or 2.8 dKH of alkalinity (6.4-7.1 ppm calcium per dKH, as Pete indicated). The reason there is some variability is due to the variable incorporation of magnesium in place of calcium in the calcium carbonate structure. Different corals use slightly different amounts.

 

[nkyreef]

The ratio of consumption is good info thanks for posting. I'm still trying to grasp how to dose properly. The four weeks prior dosing pumps were giving equal amounts of BRS 2 part (10 mL each). It always seemed like my calcium went up while my alk went down. When I stopped I lost 0.5 dKH per day over those 4 days. Using the BRS calculator, to raise my alk by 0.5 based on 45 gallon total water volume it would take 16 mL. If this is correct based upon what I've read from Randy's posts I should dose 16 mL per day calcium as well. Does this sound accurate? Should I dose 16 mL manually over a few days in addition to the pumps to get my numbers back where they need to be?

 

[Randy Holmes-Farley Verified Community Expert]

Set up your dosers for equal parts dosing based on the alk demand, then, over time, adjust the calcium doser up or down to match the long term (not daily) apparent trend in calcium changes.

 

[cracker]

Thanks Randy that's what I was wondering !

 

[Randy Holmes-Farley Verified Community Expert]

You're welcome.

Good luck.

 

[nkyreef]

Set up your dosers for equal parts dosing based on the alk demand, then, over time, adjust the calcium doser up or down to match the long term (not daily) apparent trend in calcium changes.

Thanks Randy for weighing in. In some of your previous posts you've mentioned the alk/calcium numbers get off track due to water changes. Would it be good practice to dose the amount of alk/calcium needed to restore my normal operating parameters after doing a water change? I use IO reef crystals if that makes any difference.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks Randy for weighing in. In some of your previous posts you've mentioned the alk/calcium numbers get off track due to water changes. Would it be good practice to dose the amount of alk/calcium needed to restore my normal operating parameters after doing a water change? I use IO reef crystals if that makes any difference.

IO will generally boost alk and lower calcium for most tanks doing a water change. So watching and correcting if calcium drops too much is certainly desirable.