How to calculate Calcium Carbonate as a function of alkalinity consumption?

[FranklinDattein]

Hi @Randy Holmes-Farley and fellow chemistry enthusiasts,

Is it possible to calculate the amount of dissolved calcium carbonate media by weight, as a function of alkalinity consumption? If so, how would you calculate it?
For example: 30 grams per day of calcium carbonate needs to be dissolved, to maintain 0.5dkh of consumption in 100 liters

I am looking for a formula to input the tank volume and daily alk consumption and output the amount of media required, by weight, to replenish it. Similar to how 2 part calculators do, but for calcium reactors.

I built this calculator in Google Data Studio (AU and BR prices only at the moment, sorry) to compare the running cost of most 2-3 part products on the market and I would like to update it to be able to compare 2-part products with the approximate cost of running a calcium reactor.

ps. There is also the cost of running Co2 as well, but I have an impression it isn't possible to calculate because it will vary widely depending on the reactor characteristics. It is likely to be a negligible amount, anyway.

Thanks

 

[Randy Holmes-Farley]

For alkalinity: 1 meq/L = 2.8 dKH

Each 1 mmole of carbonate adds 2 mmoles of alkalinity

Thus, 2.8 dKH contains 0.5 mmoles of carbonate in a liter

0.5 mmoles of calcium carbonate weighs 0.5 mmoles x 100 mg/mmole = 50 mg

Thus, to add 2.8 dKH to 1 L requires 50 mg of calcium carbonate

Using a calculator, the entry of sodium carbonate is quite close to calcium carbonate. It gives a requirement of media that is 6% high:

Reef Chemistry Calculator