Magnesium Supplement Calculator

Enter your aquarium water volume, current and desired magnesium level, and then select your additive of choice to find out how much you need to add to reach that desired magnesium level.




This calculator is designed to provide a single adjustment dose to correct fallen magnesium levels. Once your desired magnesium level is reached, reference the manufacturer instructions for calculating your daily dosing amount.

Keep in mind your adjustment dose will be different from your tank’s required daily dose.

If making a large adjustment (more than 100 PPM) divide the dose up and add to the tank over the course of 1-2 days to avoid dramatic changes in water chemistry.

Powdered magnesium additives should be thoroughly dissolved into solution before dosing. Dose liquid solutions slowly, into an area of high water flow.

To maintain magnesium levels once the target level has been reached, it is best to dose small amounts each day or at minimum once per week. This maintains that stability in your tank and ensures magnesium does not fall too far out of balance.

Test and monitor your magnesium levels weekly until your dosing regime is dialed and stable. In aquariums with a significant population of growing stony corals, check magnesium levels every 1-2 weeks.

Download Bulk Reef Supply Saltwater Aquarium Water Parameters Chart

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