Reef Advantage Magnesium 600 g — Magnesium 80,000 ppm Ammonia Free | Seachem

Seachem Reef Advantage Magnesium is a concentrated 80,000 ppm powdered magnesium supplement composed of an optimized blend of magnesium salts, chloride, and sulfate. It restores depleted magnesium levels with minimal impact on the ionic ratios of natural seawater. Unlike competing liquid magnesium supplements, it contains no ammonia.

Main advantages

• High concentration of 80,000 ppm — ionically balanced mixture of magnesium, chloride and sulfate
• Ammonia-free — a common contaminant in all liquid magnesium supplements on the market
• Minimal impact on the ionic ratios of natural seawater
• Economical powder format, compatible with pre-mixed solution dosing pumps

Use in reef aquariums

Magnesium plays a critical role in reef water chemistry. Severely depleted levels (below 800 mg/L) can lead to a depressed pH and an inability to maintain calcium levels. The most common causes of magnesium deficiency are the use of kalkwasser, overdosing with carbonate additives, or insufficient levels in sea salt. Kalkwasser precipitates magnesium as magnesium hydroxide—an extremely insoluble and irreversible reaction. Excess carbonates precipitate it as magnesium carbonate, which slowly redissolves. Seachem recommends maintaining magnesium levels between 1200 and 1350 mg/L.

Dosage

• Beginner: 5 g (1 level teaspoon) per 80 L (20 US gallons), twice a week. Dissolve in at least 250 ml (1 cup) of fresh water.
• Advanced: Dose until reaching 1200–1350 mg/L. Each 5 g dose per 80 L increases magnesium by 5 mg/L. Do not exceed 25 g per 80 L per day.
• Expert: determine the depletion rate and configure a continuous drip. Formula: g = v × m ÷ 80 (g = grams, v = volume in liters, m = increase in mg/L).

Guaranteed ingredient and analysis

Ingredients: magnesium sulfate, sodium chloride. Content per gram: minimum 80 mg magnesium.

Manufacturer's precautions

• Do not exceed 25 g per 80 L per day
• An excess of magnesium can accelerate the loss of carbonate alkalinity.
• Do not mix directly with a carbonate supplement — alternate days or wait at least 30 minutes
• A slight clump may form, but this does not affect use — the clumps break easily

Preparation for dosing pump

To prepare an automated dosing solution, dissolve 1 to 2 cups of Reef Advantage Magnesium in 1 L of fresh water. Calculate the weekly amount based on your aquarium's consumption rate and divide by 7 to obtain the daily dosage.

Available formats

• 300 g
• 600 g
• 1.2 kg
• 4 kg

Why choose Reef Advantage Magnesium from ReefSolution?

For a complete reef supplementation program, combine Seachem Reef Advantage Magnesium with Seachem Reef Advantage Calcium for calcium and Seachem Reef Carbonate for alkalinity. Monitor your levels with the Salifert Magnesium Test Kit or the Hanna Checker Magnesium for accurate dosing.

Frequently Asked Questions

Why is my magnesium level constantly dropping in my reef aquarium?

The most frequent causes are the use of kalkwasser (which irreversibly precipitates magnesium into hydroxide), overdosing on carbonate additives, or using sea salt with insufficient magnesium levels. Test regularly and adjust dosage accordingly.

Can Reef Advantage Magnesium be used with a dosing pump?

Yes. Dissolve 1 to 2 cups in 1 L of fresh water to create a dosing solution. Calculate the weekly amount based on your system's consumption and divide by 7 for the daily dosage.

What level of magnesium should be maintained in a reef aquarium?

Seachem recommends between 1200 and 1350 mg/L. Levels below 800 mg/L can depress the pH and prevent calcium retention.