Salifert Magnesium Aquarium Test Kit. Magnesium is present in NSW in a fairly high concentration (1300 - 1400 mg/L). Magnesium is an essential part of chlorophyll, which is necessary for photosynthesis. Without photosynthesis plants, including algae and the corals, which we usually have in our aquariums, would not be able to live. Magnesium has another important function since in fact makes maintaining the correct combination of calcium concentration and alkalinity or carbonate hardness possible. Maintaining a correct magnesium concentration is therefore very important and is indirectly responsible for fast coral and calcareous algae growth by virtue of making the maintenance of correct calcium and alkalinity figures possible. Magnesium is depleted by algae and is also depleted by the use of excessive kalkwasser and by going far beyond natural calcium and alkalinity and pH values. The Salifert magnesium test is very straightforward and does not suffer from calcium and strontium interferences when within certain bounds. It measures in sufficient accurate steps of 30 mg/L with a sharp color change. The kit can perform approx. 50 measurements.