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Reef Tank Parameters (Calcium & Magnesium)

Reef Tank Parameters - Pisces Reef Fish Emporium of Las Vegas

There are a number of parameters you need to monitor to maintain a healthy and successful reef tank (alkalinity, magnesium, calcium, etc.).

As mentioned, we are going to discuss reef parameters in a couple articles not to overwhelm because there is a lot of information to discuss. Previously, we discussed Alkalinity and pH and calcium. For a more in depth discussion, speak to your Pisces Reef staff. Also, the full articles can be viewed at and at

Magnesium is the 3rd most abundant element in saltwater. We will concentrate on the interaction between magnesium with calcium and alkalinity balance in reef aquarium. Calcium and magnesium are structurally much alike. Corals use Mg2+ by incorporating it into their skeletons. We know that Ca2+ and alkalinity have an inverse relationship. Mg2+ provides buffering capacity by bonding with carbonate ions. Mg2+ binds with Ca2+, it allows for more hardness in the water than if Mg2+ were not there. High Mg2+ levels allow for the addition of Ca2+ without the drop in alkalinity.The natural concentration of Mg2+ in seawater is approximately 1285 ppm. That is what I would aim for. Most salt mixes these days have a good amount of Mg2+ already. You could just do more water changes and over time Mg2+ levels will rise. Alternatively, you can dose a magnesium supplement. Talk with your Pisces Reef fish specialists to see what you are needing.