This product can be used on its own for a one off fix for increasing Magnesium levels in your marine/reef tank.
Maintaining Magnesium at natural sea water levels helps stabilise calcium and alkalinity levels, leading to improved growth of stony corals and calcerous algaes such as coraline and helps keep a stable pH.
You should aim to maintain Magnesium levels at around 1300 to 1350ppm using a good quality reliable test kit.
For use in aquarium to replenish lost magnesium. Use as a single correction for low magnesium levels or as part of a balanced solution using the balling method.