View Full Version : Calcium and Alkalinity Levels

10/04/2012, 05:49 PM
I have a question on calcium and alkalinity levels, depletion and testing. The reefkeeping article on their relationship states this:

1. Corals and coralline algae use calcium and alkalinity almost exclusively to deposit calcium carbonate. Because of this they use a fixed ratio of calcium to alkalinity, which is driven by the ratio of calcium and carbonate in calcium carbonate (1:1). The net consumption is about 18-20 ppm of calcium for each 1 meq/L (2.8 dKH) of alkalinity. The reason the amount of calcium varies is that the incorporation of magnesium in place of calcium varies a bit from species to species.

2. The fact that corals and coralline algae use a fixed ratio of calcium to alkalinity allows supplements to be devised that mirror this exact ratio. Using such an additive system allows accurate matching of the supplement to the demand, and does not cause rapid swings in calcium or alkalinity relative to each other if the additions are not perfect. Such balanced additives include calcium carbonate/carbon dioxide reactors, limewater/kalkwasser and two-part supplements, among others.

Hypothetically, if I only use 2 part for dosing and corals and coralline used a fixed ratio of both. Can I only test for alkalinity and trust that the calcium parameters are good?

I'm not saying cut testing calcium tests out completely, but cut back to weekly or even monthly. Does anything else deplete calcium out ratio w/calcium?

Sidenote question: how often do y'all test for magnesium?

10/04/2012, 06:15 PM
I seldom tested calcium when I was using a 2-part. Once every month or two was fine. :) Magnesium testing was about that frequent, or maybe only once every two months. Alkalinity testing was weekly or so.

10/04/2012, 06:29 PM
Thanks Jonathan.

10/04/2012, 06:37 PM
I test magnesium monthly right now because its a new tank and I seem to go through a bit more than normal due to coralline growth. I test calcium about the same, although sometimes I do go longer. I recently switched to kalk from 2 part but my calcium never differed from the expected level.

10/04/2012, 10:20 PM
You're welcome!

10/04/2012, 10:25 PM
Hi, I dropped two part, and now use a C reactor, I check cal about every 2 to 3 weeks, mag once a month, but check alk every 3 or 4 days and keep a chart of my alk - the CA reactor has been great, my alk and cal has been dead steady.

10/05/2012, 06:01 PM
I dose kalk and I do only pretty much test alk. When my alk is off, then I double-check my calcium and see if my ratios are off. I check calcium now once per month. I am really really glad people on RC like Bertoni suggested me to do this about a year ago. Good luck.

10/05/2012, 07:08 PM
i dont run 2 part but have a faithful cal reactor. after it was dialed in and fine tuned. now i only check alk every week before water change and its usually dead o at 7.8-8.2dkh range.
cal i check maybe every 2 weeks or so and its also dead on at 420. while mag is checked maybe once a month and is also right on the money 1280-1300. i use red sea regular salt. and change water 40% per month.
its all in ur testing data. i logged everything every test for every day i performed and after very careful dialing in the reactor and parameters in where i needed them i can tell testing is not much required but i do it for personal reasons and just in case.