Magnesium Supplement Calculator

Magnesium Dosing Tips

It is recommended to maintain magnesium levels at 1200-1400 ppm in a reef aquarium. Not all magnesium additives are created equal, and it is important to refer to the manufacturer's instructions before adding anything to your aquarium. Please reach out to our Customer Service team anytime to speak with a reef aquarium expert.

Before You Dose

BRS Pharma General Adjustment or 2-Part Maintenance Mix: Select BRS Liquid Magnesium Mix as the product in the calculator. The resulting dosage will be appropriate for both solutions. Both are intended to be mixed into 1 gallon of RO/DI water.
Maintenance vs. Correction: A small maintenance dose is added daily to replenish magnesium that is used by corals and to maintain stable magnesium levels in your aquarium. Large correction doses are used to adjust magnesium levels that have fallen out of an acceptable range.
General Adjustment (larger corrections over 100 pm): Spread the dose over a few days when adjusting more than 100 ppm. For example, if your required adjustment is 180 ppm, divide the calculated dose by three and add equal amounts to your aquarium over three consecutive days. Test your water chemistry in between doses to monitor your aquarium's response.
2-Part Maintenance (daily dosage): Small daily doses intended to keep magnesium levels stable in your aquarium. To be added alongside your calcium and alkalinity liquid supplements. Wait 5 days without dosing, test your magnesium levels and enter into the BRS Reef Calculator to calculate the required amount of magnesium to return your tank to optimal levels. Divide the result by 5 and you have your daily dose.
Mixing: Fully dissolve dry magnesium supplements as instructed into RO/DI water before dosing into the tank.
Where to add: Dose liquids slowly into a high-flow area, away from pumps, heaters, and other equipment to reduce precipitation.
Spacing supplements: Since magnesium will not cause precipitation like calcium and alkalinity, you can dose it within 5 minutes of your calcium or alkalinity dose without issue. Just be sure its gets dispersed in a high flow area.

After You Reach Your Target

Slow & steady: Once your target magnesium levels are reached, make small daily doses to replenish magnesium that is consumed by your corals.
Test to dial in: Test magnesium daily until consumption and dosing are matched, then switch to weekly or even bi-weekly checks.
Expect changes: As corals grow, consumption rises. You may need to increase daily dosing every few months to keep up with your tank's demand.