TBH, I would seriously consider opening that BRS box and using it, KC. Let's put the pricing in perspective. A 1 gallon container of dry calcium carbonate additive from BRS is $17. When added to water, that's about 6 gallons of additive. For SeaChem Reef Complete, you pay $32 (according to MarineDepot) for 2 liters, which is about 1/2 gallon of additive. The additive has magnesium and strontium, which you then cannot control separately, and may have too much or too little of. Each capful will raise calcium by about 10 mg/L. They say to raise the calcium by 20 ppm in a 50g tank to add 25mL of Seachem. BRS says you need 100 mL. Seachem is supposedly 4x more potent, but that 2L still only goes as far as 2 gallons of BRS solution for calcium, while not allowing you to control magnesium, which is going to be differently utilized depending on what you have in the tank. In sum, you get 3 times as much BRS solution as you do with SeaChem, at approximately half the cost of the SeaChem, and requiring about 20 minutes more work each time you need to actually make the solution. Fill bottle with RODI, pour in the amount of additive, shake - that simple.