How to Dose Magnesium in a Reef Tank

If you’re concerned about your reef tank’s pH levels, you may be wondering how to dose magnesium. This mineral is the third most abundant ion in seawater and is intimately involved in many biological processes. Too much magnesium can cause problems with calcium and alkalinity. Full strength seawater contains 1285 ppm of magnesium. It is three times more concentrated than calcium because it is lighter than calcium.

Most reef tanks require calcium, magnesium, and alkalinity dosing to maintain the optimum conditions for coral growth and health. The good news is that these parameters can be adjusted easily using aquarium test kits. Just make sure to use water that has not been dosed yet and the desired range. Once you have done this, you will know how much water your tank needs each day.

The volume of your system’s water will determine how much magnesium you need. If you have a 20-gallon display, then you’ll need about 10 ml of magnesium solution per day. If you’re concerned about your magnesium levels, you can also use the BRS Reef Calculator, which can help you find out the right dose of magnesium for your reef tank. You should always monitor the water pH levels and salinity with a test kit.

Using a supplement that contains both calcium and magnesium is a good way to maintain a proper pH balance. You can avoid calcium carbonate precipitation by keeping the magnesium level under control. But don’t forget to choose the correct magnesium for your tank because not all additives are created equal. The sulfate-to-chloride ratio will be a big factor. For large adjustments, a magnesium solution with a low sulfate concentration is better. A solution with a higher sulfate content is better for daily doses of 2 parts.

To properly dose magnesium, you should consider the type of fish you keep in your tank. Although fish food does contain magnesium, its concentrations are not high enough to significantly affect the normal magnesium levels in the water. Typical effects from foods are only between one and four ppm over a year. Magnesium in aquariens is mainly eliminated by co-precipitation of calcium carbonate in organisms, and abiotic precipitation via heaters and pumps.

Although increasing the magnesium level in a reef tank can be a good idea it is important to remember that too much or too little magnesium can have a negative impact on the health of corals and other animals. Adding magnesium is more effective than adding mineral acid. The problem with high levels of magnesium is that it depletes the mineral fast. This can be avoided by adding calcium carbonate or a magnesium supplement.

A standalone supplement is the best way to give magnesium to a reef tank. You can also use Epsom salts as a sink for magnesium, which is found naturally in seawater. You can also use magnesium calcite as a magnesium supplement if Epsom salts are not desired. However, the latter is more difficult to mix with calcium carbonate, and may coat the corals.