Free reef tool
Reef calcium dosing calculator
Enter your aquarium’s actual water volume and calcium test results to estimate a dose of Known Matter’s fully prepared calcium solution.
Raises calcium by 10 mg/L in 100 L. One 500 mL bottle provides about 80 equivalent doses at approximately $0.31 each, based on the $24.95 delivered price.
Calculator results are estimates for the fully prepared solution at approximately 160 mg calcium per mL. Confirm actual water volume, test first, make larger corrections in stages and retest. Never add the dry refill directly to the aquarium.
Before calculating
Use a recent calcium test and estimate actual water volume after rock, sand and equipment displacement. A display tank’s stated capacity is usually higher than its true water volume.
What the result means
The result is the volume of fully prepared solution—not dry refill. Make corrections gradually, allow the aquarium to circulate and retest before adding more.