Where is my calcium going?

[Modge]

Hi all - trying to figure out what's happening with my water chemistry. I am fairly new at reefing and upgraded from a 40 DT nano to a 110 DT (525 Red Sea) about a month ago.

Question I have is what would cause a significant decline in calcium from 410 ppm on 11/28 to 320 ppm on 12/12?

Here are the facts from my log:

11/27 - I began dosing Kalk at 1 tsp/gallon in my ATO. Alk tested at 7
11/28 - Measured Calc at 410ppm
11/30 - Reached a stable 8.7 Alk and has held there since
12/01 - added an additional 7lbs of live rock bringing my live rock total to around ~55lbs
12/07 - added 2/3 cup of PhosGuard after measuring phosphates at .18
12/12 - Measured Calc at 310, Phosphates tested at 0 (removed the PhosGuard media), and Alk has dropped to 8.4

I only have a handful of small LPS, a couple leathers and softies. My livestock consists of 3 giant snails, a couple of astria snails, 3 bubble bee snails, a bristle star, 15 fish (6 blue/green chromis, 2 tangs, dottyback, goby, 2 Banggai Cardinals, 2 clowns, and a red coris wrasse).

Hanna test kits for Alk and Phos - Red Sea for Calc.
Still in need of a magnesium test kit.

 

[HankstankXXL750]

I believe Alk and Ca are connected. Raising the Alk only might be the issue. I think you might need to dose Ca if your dosing for Alk.

 

[Randy Holmes-Farley]

I think the likely explanation is test error, unless you are adding large amounts of alkalinity that you are not aware of. Calcium cannot be consumed in significant amounts except by consuming 2.8 dKH of alk for each 18-20 ppm of calcium consumed.

 

[Modge]

I think the likely explanation is test error, unless you are adding large amounts of alkalinity that you are not aware of. Calcium cannot be consumed in significant amounts except by consuming 2.8 dKH of alk for each 18-20 ppm of calcium consumed.

Thanks Randy - you were correct. I retested and it came back at 400. Not sure what happened. I did have my 4 year old daughter yanking on me when I ran it earlier. So chalk the error up to "child-in-the-hood" influence.

 

[Modge]

I believe Alk and Ca are connected. Raising the Alk only might be the issue. I think you might need to dose Ca if your dosing for Alk.

I am only dosing Kalkwasser ATM - I thought that helped maintain Ca levels as well as Alk and PH stability. Am I wrong in thinking that?

 

[HankstankXXL750]

I am only dosing Kalkwasser ATM - I thought that helped maintain Ca levels as well as Alk and PH stability. Am I wrong in thinking that?

Yes my bad. I dose 2 part, and was thinking kalkwasser was only Alk.