Salifert Magnesium Test KitMagnesium is present in natural seawater 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, would not be able to live. Maintaining a correct magnesium concentration is very important, and is indirectly responsible for fast coral and calcareous algae growth by virtue of making the maintenance of correct