Balanced reef chemistry
Calcium, alkalinity and magnesium work together
Calcium is only one part of reef chemistry. Reading it alongside alkalinity and magnesium makes corrections more predictable.
Calcium
Calcium is a building material used by stony corals, clams and coralline algae. A calcium supplement replaces what those organisms and chemical processes remove.
Alkalinity
Alkalinity supports calcification and helps resist rapid pH change. It is often consumed alongside calcium, but the two measurements are tested and adjusted separately.
Magnesium
Magnesium helps calcium and carbonate remain available in seawater. A low or inaccurate magnesium reading can make calcium and alkalinity appear harder to stabilise.
A practical order
Check salinity first, then test magnesium, calcium and alkalinity with reliable methods. Correct large imbalances gradually and avoid adding concentrated calcium and alkalinity solutions at the same time or in the same container.