[Red Sea] Foundation Magnesium 16.9floz

Red Sea Reef Foundation C — Magnesium (500 mL / 16.9 fl. oz.)

Transform Your Tank with the Missing Link in Reef Chemistry

Looking for the foundation element most reef keepers overlook? Red Sea Reef Foundation C Magnesium is a hobbyist staple at The Coral Boutique, trusted by reef keepers who understand that calcium and alkalinity simply won't stay in balance without it. This 500 mL bottle is sized perfectly for nano and mid-sized reef systems running manual or automated dosing.

Reef Foundation C is a high-purity liquid magnesium complex formulated to maintain stable Mg levels in the seawater-correct ratio. Magnesium plays a critical behind-the-scenes role in reef chemistry — it prevents calcium and carbonate from precipitating out of solution, keeps your dosing efficient, and is essential for healthy coralline algae growth and overall coral skeletal development. When Mg drops too low, you'll see calcium and alkalinity become impossible to hold steady no matter how much you dose, plus coralline coverage stalls. Red Sea recommends maintaining magnesium between 1,250–1,390 ppm to keep the entire foundation chemistry locked in. Reef Foundation C is part of Red Sea's complete Reef Care Program, designed to be dosed alongside Foundation A (Calcium) and Foundation B (Alkalinity) to keep all three core parameters in true balance. Ready-to-use straight from the bottle — no mixing, no stock solutions — it works equally well with manual dosing or a dosing pump for the kind of stability your corals reward you for.

Key Benefits

• High-purity liquid magnesium complex in seawater-correct ratios
• Prevents calcium and alkalinity precipitation, keeping dosing predictable
• Promotes strong coralline algae growth and vibrant coral skeletal development
• Stabilizes the entire reef foundation chemistry trio
• Ready-to-use formula — no mixing required, no stock solution needed
• Ideal for both manual dosing and automatic dosing pumps
• Part of the complete Red Sea Reef Care Program for balanced reef chemistry
• Concentrated formulation — efficient dosing for nano and mid-sized reefs

Quick Stats & Dosing Guide Product Name: Red Sea Reef Foundation C — Magnesium Manufacturer: Red Sea Size: 500 mL (16.9 fl. oz.) Active Ingredients: Magnesium complex (in coral-skeleton ratios) Form: Ready-to-use liquid supplement Target Magnesium Range: 1,250–1,390 ppm Dosing Rate: 1 mL raises Mg by approximately 1 ppm in 100 liters (25 gallons) Recommended For: Reef aquariums up to 500 liters (125 gallons) Best Practice: Dose according to measured magnesium uptake using Red Sea's Foundation Pro multi-test kit Compatibility: Works alongside Reef Foundation A (Calcium) and Reef Foundation B (Alkalinity) for complete balance Best For: Reef keepers running mixed reefs, SPS-dominant systems, or any saltwater aquarium where precise magnesium control matters Directions: Test magnesium levels regularly. Add directly to a high-flow area of the sump or display, or use with a dosing pump. Magnesium can be dosed at any time and is not subject to the same precipitation timing as Foundation A and B.

Why Buy From The Coral Boutique?

At The Coral Boutique, we stock only the supplements and additives we trust on our own systems. Red Sea's Reef Foundation C Magnesium is a long-standing favorite in the saltwater aquarium hobby because it locks in the foundation chemistry that calcium and alkalinity dosing depend on. Every product on our shelves is tested, vetted, and backed by reefers who actually use it — so you can buy with confidence.