DIY Magnesium (Randy Recipe 3A) Magnesium Dosing Calculator

DIY Magnesium (Randy Recipe 3A) raises magnesium by 0.4694 ppm per mL per 100 L of tank water (manufacturer data: source). Enter your tank volume, current and target magnesium below for an exact dose, split automatically if it exceeds the safe daily limit.

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Worked example

A 75 gallon tank (284 L) raising magnesium by 20 ppm needs (20 / 0.4694) x (284 / 100) = 121 mL of DIY Magnesium (Randy Recipe 3A).

Safe dosing rules

• Never raise magnesium more than 100 ppm per day.
• Test again before each additional day of a split correction.
• Dose into high flow, away from coral tissue and intakes.