In a reef aquarium, maintaining the right balance of calcium (Ca), alkalinity (KH), and magnesium (Mg) is essential to coral health, growth, and skeletal formation. These three major elements form the structural foundation of hard corals and coralline algae, and even slight imbalances can lead to coral stress, poor coloration, and stunted development.
Red Sea’s Reef Foundation A, B, and C supplements are designed to work in harmony, providing a precise, balanced system for dosing these critical elements. In this guide, you’ll learn why each of these elements matters, how they interact, and how Red Sea’s Foundation line simplifies their management.
Why Calcium, KH, and Magnesium Are Called “Foundation Elements”
In reef aquariums, calcium, alkalinity, and magnesium form the building blocks of coral skeletons. Without these in the correct proportions, corals cannot grow, and water stability begins to decline.
Calcium (Ca)
Calcium is required by all hard corals to form their calcium carbonate skeletons. It’s also used by clams, snails, and coralline algae. The ideal range in a reef tank is
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430–450 ppm
When calcium levels drop, corals may stop growing, and tissue can recede or bleach.
Alkalinity (KH)
Alkalinity represents the concentration of carbonate and bicarbonate ions in the water—these are the buffers that maintain pH stability and combine with calcium to form coral skeletons. The ideal KH range is:
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8–9 dKH
Low alkalinity leads to pH instability and poor calcification. High alkalinity can cause precipitation and stress.
Magnesium (Mg)
Mgnesium doesn’t directly build coral skeletons, but it regulates the ratio between calcium and alkalinity, preventing them from precipitating out of solution. It also supports coral coloration and metabolic function. Ideal range:
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1280–1350 ppm
Without enough magnesium, it becomes almost impossible to maintain stable calcium and alkalinity levels.
How Red Sea Foundation A, B & C Work Together
Red Sea’s supplements deliver each of these elements individually, allowing you to dose according to your tank’s specific needs.
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Foundation A (Calcium + Strontium + Barium)
Promotes strong skeletal growth with additional trace elements for density.
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Foundation B (KH Buffer)
Stabilizes pH and supports calcification with balanced carbonate content.
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Foundation C (Magnesium)
Enhances element solubility and maintains ionic balance in reef systems.
These are highly concentrated and designed to match the uptake rates in mixed and SPS-dominant tanks. Red Sea recommends using them in tandem with their Reef Foundation Pro Test Kit for accurate monitoring.
How to Dose Red Sea Foundation Supplements
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Test your water regularly using Red Sea’s Pro kits.
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Match your test results to Red Sea’s dosing chart.
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Dose manually or via a dosing pump like ReefDose for consistency.
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Always dose separately, not at the same time, to avoid precipitation.
Dosing schedules can be daily or weekly, depending on coral demand and stocking levels.
The Importance of Balance
The Red Sea Reef Care Program emphasizes ionic balance. Dosing Foundation A, B, and C in the right proportions keeps your water stable and prevents swings that can damage coral health. Using Red Sea salt mixes, test kits, and supplements together helps ensure long-term compatibility.
Final Thoughts
If you want to grow vibrant, structurally sound corals, you can’t ignore calcium, alkalinity, and magnesium. Red Sea’s Foundation A, B & C supplements offer a research-backed, reef-safe way to manage these parameters precisely.
