Balance between Calcium, Alkalinity and Magnesium

[Arkonen]

Is there a formula or method to determine what my levels should be of each type to be balanced?  For example:

 

If calcium is 450, my alkalinity should be ____ dkH, and magnesium should be ____ ppm.

If alkalinity is 10 my calcium should be ____ ppm, and magnesium should be ____ ppm.

If magnesium is 1350 ppm my calcium should be ____ ppm, and alkalinity should be ____ dkH

 

I know that calcium should be between 400-440ish, and alkalinity between 7-12 dkH, and magnesium between 1300-1500 ppm, but it would be beneficial to see HOW they are supposed to be balanced with each other.  I've seen other calculators such as http://www.ultimatereef.net/info/calculators/alkcalcalc.php that do calcium and alkalinity, but nothing that also includes magnesium.  

 

Thoughts?

[mr.x-ray]

Yes it should be. Origami has a chart in his photo gallery for calcium and alk balance. Mag should be approx. 3x amount of calcium. ie. calc is 400 mag should be 1200.

[surf&turf]

http://reef.diesyst.com/chemcalc/chemcalc.html

 

 

This one is pretty good. 

[dave w]

The best illustrations I've read came from Julian Sprung's reef aquarium books.  He really made that complex subject more clear for me.  He used graphs that had 3 or 4 variables involved.  Sorry, I can't remember which of the three books it was in.  I can check for you tonight if you want.

[Origami]

I use the Reef Chemistry Calculator linked to above, actually.

 

If you want a formula, it works out to be something like this:

 

Ca_ppm = 360 + 7.14 * alk_dKH  << This calculates your balanced calcium level given your alk level (measured in dKH)

 

Alk_dKH = (Ca_ppm - 360) / 7.14

 

There really isn't a "balanced magnesium" level as it is not consumed consistently proportionally. Instead, magnesium is often kept between 1280 ppm and 1500+ ppm depending upon the aquarist's preference.

 

I've memorized a variety of quick facts over the years. One is that, ideally, 20 ppm of calcium is consumed for every milliequivalent per liter of alkalinity consumed in the production of calcium carbonate (coral skeleton). There are 2.8 dKH in 1 meq/l.  This results in the constant that you see above. 20 divided by 2.8 is 7.14.

[icsparks]

 

Balanced Calcium and Alkalinity

 

360 ppm to 0 dKH

 

370 ppm to 1.4 dKH

 

380 ppm to 2.8 dKH

 

390 ppm to 4.2 dKH

 

400 ppm to 5.6 dKH

 

410 ppm to 7 dKH (natural seawater)

 

420 ppm to 8.4 dKH

 

430 ppm to 9.8 dKH

 

440 ppm to 11.2 dKH

 

450 ppm to 12.6 dKH

 

460 ppm to 14 dKH

 

[Arkonen]

Thanks guys for all your input

[zygote2k]

What it should be and what it is are 2 very different scenarios. I've never witnessed a 'balanced' aquarium.

[Origami]

What it should be and what it is are 2 very different scenarios. I've never witnessed a 'balanced' aquarium.

Maybe you have but you just didn't know it.

 

"Balanced" by the way is a term that should be explained. When you look at "average" natural saltwater (keeping in mind that there is probably no single place on earth that always meets this definition), there's a certain balance of calcium and alkalinity. This establishes a point-reference. From there, you extrapolate a line that increases alkalinity by 1 meq/liter (or 2.8 dKH) for every 20 ppm of calcium. That ratio corresponds to the theoretical consumption of alkalinity and calcium in the formation of calcium carbonate. There's nothing particularly magical about being in "balance." Of course, if you're really out of balance, there can be negative implications but, for the most part, if your coral has one calcium ion and a couple of bicarbonate ions available to it, it's going to try to lock onto them and add to it's skeleton. But, when you're in "balance" your tank should maintain "balance" with normal consumption and balanced additives should keep you on this balance line. It's this consumption ratio that sets, for example, the ratio used in two-part dosing. Deviations from this consumption ratio can indicate other issues in the tank - for example, nitrate problems.

 

So, whether you know it or not, the idea of "balance" is affecting your reefkeeping protocol, regardless of if you're using kalkwasser, two part, or a calcium reactor.

[s2nhle]

Thanks for information sharing.