Magnesium in your Stony Reef

---

     Magnesium is often one of the most overlooked properties of your reef’s synthetic seawater and although this is one of the most important factors considered in growth and health of most stony corals. Just like calcium and alkalinity magnesium is depleted by your reef inhabitants. It is also an important factor in maintaining stable calcium and alkalinity levels.

Just like all other ions in a reef tank you want to produce levels as close to natural seawater as possible. For this reason maintaining a level of at least 1290 to 1400ppm of magnesium is critical. Speaking from experience most stony corals will show lack of growth around 1100ppm and start declining in health at around 1000 or 900ppm.

There are many ways to keep your magnesium levels as stable as possible.

• Magnesium supplements such as Tropic Marin, Kent Marine or Bulk Magnesium Chloride.
• Using Salts that have high magnesium Content. Many Salts use half the recommended amount to stay inexpensive.
• Frequent Water changes with a high magnesium Salt such as Oceanic Salt Mix( My personal preference.

As noted in bullet number 2 when maintaining a reef aquarium it is critical that you use a salt mix formulated for a reef environment. Generally more costly than regular salts such as instant ocean it will save you money and less loss of inhabitants in the long run.

Magnesium is the 3rd most abundant ion in natural seawater, first being sodium and second being chloride it is often overlooked until there is a problem by aquarist’s. I have personally tested a tank with magnesium deficiency and most cultured corals significantly lack in growth and many slowly bleach and STN(slow tissue necrosis). Polyp extension is highly lacking as well. After raising the magnesium level to the correct range we noticed almost immediately increased polyp extension and over a few days increased growth in the tips of cultured corals. Make sure to raise these levels slowly as you would any other parameter.

In essence maintaining a healthy growing reef environment requires that your magnesium not be overlooked. Frequent testing and use of high quality supplements and salt mixes will make this process much easier and save you money in the long run.