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Alk\Calc Ratio
- Thread starter ecam
- Start date
Here's my canned answer to this question:
[FONT=&]The uptake of Ca and Alk, by “stony” type coral, coralline algae, etc. in a reef system is[/FONT][FONT=&]20 ppm Ca to 50 ppm(2.8dKH) Alk(CaCO3), which is a ratio of 2 pts Ca to 5 pts Alk (2:5)[/FONT][FONT=&]. Equal doses of any two part supplements are designed to provide the same ratio's. So, they will all work but, I have found that the brand name products are going to be more expensive. I use one of the BRS (Randy’s) recipes. I considered using the Dow flake, etc., but just can't get my head wrapped around the fact that something that is used in your driveway to melt snow and ice is going to be pure enough to add to an aquarium. So I buy both the Calcium Chloride and Soda Ash from BRS, although I have used A&H Baking Soda as well.
Saturated kalkwasser also contains this same ratio, @ ~ 800 ppm Ca(2pts.) to 2,000 ppm CaCO3(5pts.). It also has the added benefit of utilizing some of the CO2 in your system, which may help keep your pH in line. Even though I'm using a two part recipe, I also still use the kalk in my dosing regimen. The problem with kalk is that it’s limited in its ability to keep up with a high demand due to the fact that you’re limited to how much you can add to RO/DI water (2tsp.), and your evaporation rate. You can boost that to 3 tsp. with the addition of vinegar, but that also adds a carbon source, and potentially other issues.
I'd make sure the salinity is right, by measuring it using a calibrated (@35ppt) refractometer, or metering device. This will ensure you are adding enough Ca, Alk and Mg when you do your WC's. With normal WC's mixed to a salinity of 1.026, using a "reef" grade of salt mix, i.e. Reef Crystals, I've never had to add Mg.[/FONT]
[FONT=&]The uptake of Ca and Alk, by “stony” type coral, coralline algae, etc. in a reef system is[/FONT][FONT=&]20 ppm Ca to 50 ppm(2.8dKH) Alk(CaCO3), which is a ratio of 2 pts Ca to 5 pts Alk (2:5)[/FONT][FONT=&]. Equal doses of any two part supplements are designed to provide the same ratio's. So, they will all work but, I have found that the brand name products are going to be more expensive. I use one of the BRS (Randy’s) recipes. I considered using the Dow flake, etc., but just can't get my head wrapped around the fact that something that is used in your driveway to melt snow and ice is going to be pure enough to add to an aquarium. So I buy both the Calcium Chloride and Soda Ash from BRS, although I have used A&H Baking Soda as well.
Saturated kalkwasser also contains this same ratio, @ ~ 800 ppm Ca(2pts.) to 2,000 ppm CaCO3(5pts.). It also has the added benefit of utilizing some of the CO2 in your system, which may help keep your pH in line. Even though I'm using a two part recipe, I also still use the kalk in my dosing regimen. The problem with kalk is that it’s limited in its ability to keep up with a high demand due to the fact that you’re limited to how much you can add to RO/DI water (2tsp.), and your evaporation rate. You can boost that to 3 tsp. with the addition of vinegar, but that also adds a carbon source, and potentially other issues.
I'd make sure the salinity is right, by measuring it using a calibrated (@35ppt) refractometer, or metering device. This will ensure you are adding enough Ca, Alk and Mg when you do your WC's. With normal WC's mixed to a salinity of 1.026, using a "reef" grade of salt mix, i.e. Reef Crystals, I've never had to add Mg.[/FONT]
Is there a predictable consumption rate of mag? I personally assume 1ppm a day after some research... hope you don't mind the hijack OP.
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The chemist's answer is two moles of alkalinity are lost for every one mole of calcium. As mentioned, all two part solutions are made to provide this equivalence by adding equal volumes of each. Note that this is not an exact science since magnesium and strontium can take the place of calcium and offset this ratio slightly. That is why you want to test and adjust volumes accordingly.
From the hyperlink in response #2:
"There are many good ways to provide a balanced ratio of calcium and alkalinity. Before discussing the methods, let me explain a bit more about what a balanced ratio actually is. Pure calcium carbonate contains one calcium ion for each carbonate ion. That ratio corresponds to 1 meq/L of alkalinity (= 2.8 dKH or 50 ppm calcium carbonate equivalents) for each 20 ppm of calcium. In a real coral skeleton, some magnesium ions get into spaces ordinarily occupied by calcium, so the real ratio in corals and coralline algae is usually closer to 18-20 ppm calcium for each 1 meq/L of alkalinity, and that ratio varies a bit by organism."
So, some Mg will be used depending on the organism, but it would be hard to predict. I think with regular WC's, at a consistent SG, it will not be a problem.