Reef Advantage Calcium 4 kg — Ionic Calcium pH 8.3 with Mg and Sr | Seachem

Seachem Reef Advantage Calcium in a 4 kg format is a non-caustic (pH 8.3–8.6) powdered ionic calcium supplement formulated to restore and maintain calcium levels in reef aquariums. It includes magnesium and strontium in proportions corresponding to typical usage ratios (100:5:0.1, Ca:Mg:Sr). The 4 kg format is the largest in the range, designed for large reef systems, multiple systems, or aquarists using long-term automated dosing.

Main advantages

• Concentrated ionic calcium powder — 5 g per 150 L increases calcium by 12 mg/L
• Non-caustic pH (8.3–8.6) — without risk of fluctuation, unlike kalkwasser
• Includes magnesium and strontium in natural ratios (100:5:0.1, Ca:Mg:Sr)
• 4 kg format — the most economical in the range, ideal for large systems and long-term dosing
• Compatible with pre-mixed solution dosing pumps

Use in reef aquariums

Calcium is essential for the growth of all corals and coralline algae. A deficiency causes growth to stop, followed by a rapid decline in coral health. Reef Advantage Calcium differs from kalkwasser in that it maintains a safe pH of 8.3–8.6 and includes magnesium and strontium without additional supplementation. Seachem recommends maintaining calcium levels between 380 and 420 mg/L with an alkalinity between 3 and 6 meq/L (8–17 dKH).

Dosage

• Beginner: 5 g (1 level teaspoon) per 150 L (40 US gallons), twice a week. Dissolve in at least 250 ml (1 cup) of fresh water.
• Advanced: Dose until reaching 380–420 mg/L. Each 5 g dose per 150 L increases calcium by 12 mg/L. Do not exceed 10 g per 150 L per day.
• Expert: determine the consumption rate and configure a continuous drip. Formula: m = v × c ÷ 400 (m = grams, v = volume in liters, c = increase in mg/L).

Ingredients and guaranteed analysis

Ingredients: calcium chloride, magnesium chloride, strontium chloride.

• Calcium (min): 335 mg/g — (max): 347 mg/g
• Magnesium (min): 17 mg/g
• Strontium (min): 0.34 mg/g

Preparation for dosing pump

To create an automated dosing solution, dissolve 165 to 200 g in 1 L of RO/DI water. The 4 kg format allows you to prepare more than 20 liters of concentrated solution. Calculate the weekly quantity based on your system's consumption rate and divide by 7 for daily dosing.

Manufacturer's precautions

• Do not exceed 10 g per 150 L per day
• Excess calcium can accelerate the loss of carbonate alkalinity.
• Do not mix directly with a carbonate supplement — alternate days or wait at least 30 minutes
• Causes serious eye irritation — keep out of reach of children, avoid skin contact

Available formats

• 250 g
• 500 g
• 1 kg
• 4 kg

Why choose Reef Advantage Calcium from ReefSolution?

The 4 kg format is the most cost-effective choice for serious aquarists. For a complete reef program, combine Seachem Reef Advantage Calcium with Seachem Reef Carbonate for alkalinity and Seachem Reef Advantage Magnesium for magnesium. Monitor your parameters with the Salifert Calcium Test Kit or the Hanna Checker Calcium and automate your dosing with the Kamoer X1 Pro Dosing Pump.

Frequently Asked Questions

Is the 4kg format the most economical for large reef aquariums?

Yes. The 4 kg size is the largest in the range and offers the best cost per gram. It allows you to prepare more than 20 liters of concentrated solution for dosing pumps, ideal for systems over 100 gallons with high calcium demand.

How long does a 4kg format last?

At a starting dosage of 5g twice a week for a 150L aquarium, a 4kg package lasts for 800 doses, or approximately 7 to 8 years. For SPS tanks with high consumption, dosed daily, the duration varies depending on the volume and the system's demand.

Does Reef Advantage Calcium replace strontium and magnesium supplements?

Partially. The product includes Mg and Sr in typical usage ratios (100:5:0.1). For large, high-demand SPS systems, supplementation with Seachem Reef Advantage Magnesium may be required depending on test results.