One level measuring spoon increases the magnesium level of 30 gallons of tank water by about 5 ppm. The natural concentration of Magnesium is 1280-1300 ppm. In a reef aquarium the concentration of magnesium decreases quickly through biological process, precipitation and through use by calcareous animals. The recommended maximum dose is 4 measuring spoons per 30 gallons of aquarium water per day! Check the specific gravity of the aquarium water on a regular basis as this may gradually increase over time with the addition of Tropic Marin Bio-Magnesium. This is easily counteracted with regular water changes. An excessively high magnesium concentration may have a negative effect on certain organisms. For this reason it is not recommended to exceed magnesium concentrations over 1600 ppm.