Techniques For Maintaining Calcium And Alkalinity In Reef Tanks

By Than Thein

Calcium and alkalinity are vitally important chemical parameters in reef aquariums. They are used by stony corals to build their calcium carbonate skeletons. A lack of calcium and alkalinity in the water will inhibit the growth of reef-building corals and invertebrates, which will eventually lead to health problems.

What is calcium?

Calcium is one of the major ions in salt water. It is the fifth most common ion in salt water behind, chloride, sodium, sulfate, and magnesium. In most healthy reefs, the calcium level hovers around 425 parts per million (ppm). It regularly pairs with anions such as sulfate, carbonate, and bicarbonate in solution.

What is alkalinity?

Alkalinity is a little more difficult to explain than calcium. It is not a particular ion, but rather the buffering capacity of salt water. Buffering capacity can be thought of as the amount of acid required to lower the pH of salt water to the point that bicarbonate turns into carbonic acid. It sounds overly technical, but in layman’s terms, higher alkalinity levels equal greater chemical stability in our reef tanks.

Maintaining calcium and alkalinity

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