What ratio should a tank use calcium to alkalinity?

[azbigjohn]

I realize this may not be an completely answerable question, but I started a new, 210 gallon aquarium and fuge 4 months ago, and have added several frags to it (mixed, but several SPS, along with zoas, nepthia, acans and hammers). I have been checking my "big three" every two days, trying to determine my daily need, so that I can bring a doser online eventually when my uptake gets high enough. I should note that the total water volume of aquarium and sump is 200 gallons.

I try to aim for my levels to be:

SG - 1.026
Alkalinity - 8.8 dKh
Calcium 450 ppm
Magnesium 1300 ppm

I realize this may all be perspective from the different labels, but it seems my tank is sucking up alkalinity, but only a little bit of calcium.

Every two days, I find my alkalinity usually down 0.7 to 0.8 dKh, and my calcium is usually only down 10 ppm, if that even. I expect magnesium to not waver much (I have added Magnesium once in three weeks).

Not sure if it matters, the tank was started with all new, dry Marco rock, and has about a 1 1/2" aragonite sand bed. Current inhabitants are only a small CUC, two large Ocellarius clowns, a Large PJ Cardnial and a BiColor blenny.

Any thoughts on if my tank is gulping down alkalinity, or is it just my perception is off?

 

[reeferfoxx]

I use this calculator to help me with dosing --->Here.

I believe Randy helped with these calculations as it references a thank you message to him.
Once you punch in your alkalinity level and target level w/ the selected product, then it will tell you the balanced level. Calcium ranges can vary and won't negatively impact tank. I however go by this calc. with balanced Ca and Dkh and can maintain equal dosings on the daily. BTW I dose two part.

 

[azbigjohn]

Thanks for the link to the calculator. I have seen this in the past, but I must say I do not completely understand what it is meaning when it gives me a "balanced Calcium" under the alkalinity, and likewise a balanced alkalinity under the calcium. The "goal" numbers and the "balanced" number seem to have nothing to do with each other...

Think its time to go read Randy's chemistry articles again...

 

[reeferfoxx]

Think its time to go read Randy's chemistry articles again...

This is a good one Here.
Once I figured out my stable nutrient levels, I adjust my alkalinity for that range, and keep calcium "balanced" with alk.

 

[Randy Holmes-Farley Verified Community Expert]

Tanks generally use about 18-20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity. That's the ratio deposited into coral skeletons.

There are a few things that mess with this ratio, such as big rises or falls in nitrate (not steady nitrate, regardless of level), sulfur denitrators, and water changes with a mix not matching the tank.

This has more:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

 

[azbigjohn]

Tanks generally use about 18-20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity. That's the ratio deposited into coral skeletons.

There are a few things that mess with this ratio, such as big rises or falls in nitrate (not steady nitrate, regardless of level), sulfur denitrators, and water changes with a mix not matching the tank.

This has more:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

Thanks, Randy,

So, using that figure, I guess my big concern about my tank only using 10 ppm of Calcium for every 1 dKH of alkalinity was actually not too far out of whack. If anything, my tank is a little behind on sucking up alkalinity!

 

[Karliefish]

Tanks generally use about 18-20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity. That's the ratio deposited into coral skeletons.

There are a few things that mess with this ratio, such as big rises or falls in nitrate (not steady nitrate, regardless of level), sulfur denitrators, and water changes with a mix not matching the tank.

This has more:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

Randy question on the calculator…I don’t see Tropic Marin All-ForReef as a choice. What should I select if this is what’s I’m using to supplement my tank?

 

[Randy Holmes-Farley Verified Community Expert]

Randy question on the calculator…I don’t see Tropic Marin All-ForReef as a choice. What should I select if this is what’s I’m using to supplement my tank?

I don't know of a calculator for it.

From this comment:

Where can I find the dosing calculator for Tropic Marin All for Reef (AFR)?

I remember it used to be at the bottom of the tropic marin site but it's no longer there. Does anyone know where I can find it again? My alk is currently 6.7 and I want to raise it to 8.0 (tank volume is 95 gallons). The instructions only say to add 5ml per 25 gallons but I have no idea how...

www.reef2reef.com

This means for example 10 ml contain 60 dKH alkalinity and dosed to 100 l/26.4 US-gallon of water it raises the alkalinity by 0.6 dKH.

If you want to use a calculator, use this one and the entry for my DIY #1, and then multiply the amount needed by 0.88 (meaning you need just a little less AFR than my two part #1 to provide the same alk (or calcium).

Reef Chemistry Calculator