Benefits of Magnesium in Saltwater Aquariums

Often overlooked, magnesium plays a critical role in chemical and biological processes in an aquarist's saltwater aquarium. The magnesium content in natural saltwater is only behind that of sodium and chloride, making it a major element as opposed to a trace element. Magnesium is essential to all organisms for biological functions, and is very important to organisms that are skeleton building such as LPS and SPS corals.

Many times we find hobbyists that are struggling with issues in their coral reef aquarium only to find deficiencies in magnesium. It is very difficult to maintain ideal calcium and alkalinity levels in saltwater without maintaining magnesium levels as well. Natural sea water has magnesium concentrations of 1280-1350 ppm. If the levels in an aquarium are below these levels, calcium and carbonates will tend to precipitate out causing issues, mainly with corals. Therefore, we suggest if you are not achieving intended results, you should check your magnesium levels on a regular basis and dose as needed.

 

Magnesium may be found in saltwater mixes. Many of the "reef" mixes will have added higher concentrations of magnesium and other elements in the concoctions. Magnesium can also be found in the proper breakdown of materials such as aragonite in a calcium reactor set-up. However, the easiest way to dose magnesium is to use a liquid or a powdered form of a stand-alone supplement such as aquavitro ions™.

 

Before dosing anything, you need to know where you're starting, so test your aquarium's water. Magnesium levels in a reef aquarium should be between 1250 and 1350 ppm. Since each aquarium is different, it will use magnesium at its own rate. Typically, aquarists keeping fish-only tanks do not have problems with low levels of magnesium, as the major element is used slowly in this type of set-up. As it is used, it is replenished during water changes with quality salt mixes.

The aquarist keeping live rock, a mix of soft corals and maybe a few stony corals will have a higher magnesium demand than a fish-only tank. Maintaining magnesium levels in this type of set-up will usually need a general all-around supplement in addition to water changes. Products such as  Seachem Reef Complete™ are a good place to start if the magnesium isn't being used at a high rate.

Hobbyists maintaining higher concentrations of LPS, and especially SPS, will have a much higher demand for magnesium to coincide with the higher usage of calcium and carbonate (alkalinity) in their aquarium. Generally speaking, aquarists with higher concentrations of stony corals also have more of a tendency to be hands-on in their aquarium so testing and dosing magnesium as a stand-alone product should not be a big deal. Products such as the previously mentioned aquavitro ions™, along with Continuum reef basis magnesium™, Tropic Marin Bio-Magnesium™ and Kent Tech M™ can all serve this purpose.