Calcium
Ca2+Definition
Calcium (Ca2+) is the cation that combines with carbonate to form coral skeletons (CaCO3). Reef tanks consume calcium as coral grows.
Practical use
Reef target: 420-450 ppm. Test weekly; supplement via 2-part dosing, kalkwasser, or calcium reactor. Pair with magnesium - low Mg prevents Ca/Alk uptake.
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