The DALUA collaboration with Coral Essentials. Magnesium plus traces is a concentrated source of liquid magnesium, 20,000 ppm (mg/L). Coral take up magnesium into their calcium carbonate skeletons. It is important to maintain adequate magnesium levels as this is essential in maintaining correct calcium and alkalinity levels. Poor magnesium levels usually result in the need for addition of much higher levels of calcium and carbonate than would normally be required. It serves to prevent the excessive precipitation of calcium carbonate from aquarium water. The magnesium levels in marine tanks need to be checked regularly to determine the uptake in your system.