Dose Your Calcium Correction
Enter your current and target calcium and we'll work out how much to dose – based on Red Sea Reef Foundation A's published rate, split safely across days if the correction is a big one.
Based on Red Sea Reef Foundation A's published rate: 1 mL per 100 L raises calcium by about 2 ppm. Dosing a different calcium product? Check its own label – dosing strength varies by brand.
FAQ
How much should I dose to raise my calcium?
Test your current calcium first, then use the calculator above – it's built on Red Sea Reef Foundation A's stated rate of 1 mL per 100 L for roughly 2 ppm of calcium. If you're dosing a different brand, check that product's own label; strengths vary.
Is there a limit to how fast I can raise calcium?
Yes – Red Sea specifically advises against raising calcium by more than 20 ppm in a day. A fast jump can throw off the balance with alkalinity and magnesium, and in tanks with already-high alkalinity, can cause cloudiness as calcium carbonate precipitates out of solution.
What calcium level should I be targeting?
Most reef tanks are kept somewhere around 400–450 ppm, close to natural seawater. Stony corals, clams and coralline algae are the main consumers – a fish-only or soft-coral-only tank generally has much lower demand and needs less frequent dosing.
Why does my calcium keep dropping even though I dose it?
Usually low magnesium. Magnesium is what keeps calcium and alkalinity from reacting and precipitating out of the water – if calcium won't hold no matter how carefully you dose it, check magnesium before dosing more calcium. See our Magnesium Dosing Calculator and Alkalinity Dosing Calculator.
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Dosing rate above is Red Sea Foundation A's published figure. Using Reef Fusion or another brand? Check its own label before dosing – rates differ.