Calcium is a source of huge debate when it comes to reefkeeprs. Unfortunately, there is a lot of confusion when it comes to calcium in the water, much like there is about pH levels. Many reef animals utilize calcium to live and grow. Some of these depend on calcium in the water to create their skeletons. Whereas many animals (including humans) are able to take up calcium through the foods they eat, these sessile organisms in the reef have to rely on ambient levels of calcium, gradually absorbing it through their tissue.

Corals are the number one type of organism that needs calcium present in the water to grow, and since this is the goal of the reefkeepers, it makes sense to ensure there is enough calcium available for corals to grow. To measure calcium, we use test kits that measure in parts per million, or ppm. The ocean contains calcium levels of 400-420 ppm, and this is what we aim for in the aquarium.

There are many ways to introduce calcium into the water, but by far the easiest is simply to do water changes. Synthetic sea salt mixes contain many salts in them, including ones that have calcium. Performing frequent water changes is one excellent way to keep calcium levels high.