Dose Your Magnesium Correction
Enter your current and target magnesium and we'll work out how much to dose – based on Red Sea Reef Foundation C's published rate, split safely across days if the correction is a big one.
Based on Red Sea Reef Foundation C's published rate: 1 mL per 100 L raises magnesium by 1 ppm. Dosing a different magnesium product? Check its own label – dosing strength varies by brand.
FAQ
How much should I dose to raise my magnesium?
Test your current magnesium first, then use the calculator above – it's built on Red Sea Reef Foundation C's stated rate of 1 mL per 100 L for 1 ppm of magnesium. If you're dosing a different brand, check that product's own label; strengths vary.
How fast can I raise magnesium?
Red Sea's own guidance is to split any correction over about 20 ppm across several days. Community experience on how fast magnesium itself can safely move varies quite a bit – the more consistent concern raised by reef chemistry writers is product purity (impurities in cheap magnesium sources), not the magnesium level itself, which is another reason to stick to a reputable brand.
What magnesium level should I be targeting?
Most reef tanks are kept in the 1,250–1,350 ppm range, close to natural seawater, which is what lets calcium and alkalinity hold their levels without precipitating out of solution.
My calcium and alkalinity won't stay balanced – could this be why?
Very possibly. Low magnesium is one of the most common reasons calcium and alkalinity seem to "fight" no matter how carefully they're dosed – check magnesium before adjusting either one further. See our Calcium and Alkalinity dosing calculators.
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Dosing rate above is Red Sea Foundation C's published figure. Using a different brand? Check its own label before dosing – rates differ.