Measured corrections
How to raise calcium safely in a reef tank
A calcium correction should begin with a reliable test result—not a routine dose or a guess.
1. Test before dosing
Confirm the result with a correctly used test kit. If a reading is surprising, repeat the test before making a large change.
2. Estimate actual water volume
Subtract the displacement from rock, sand and equipment. Overestimating water volume produces an oversized dose.
3. Calculate the prepared-solution dose
Use the current result, target and actual litres. The Known Matter calculator is based on the fully prepared solution at approximately 160 mg calcium per mL.
4. Correct gradually and retest
Split larger corrections, allow water to circulate and retest. Once the target is stable, measure daily consumption and dose only what the aquarium uses.
Keep calcium and alkalinity additions separate
Do not mix concentrated calcium and alkalinity supplements together. Add them separately in a high-flow area so each can disperse.