Reef Advantage Calcium 500 g — Ionic Calcium pH 8.3 with Mg and Sr | Seachem

Seachem Reef Advantage Calcium in a 500g format is a non-caustic (pH 8.3–8.6) powdered ionic calcium supplement formulated to restore and maintain calcium levels at natural seawater levels in reef aquariums. Its formula includes magnesium and strontium in proportions corresponding to typical usage ratios (100:5:0.1, Ca:Mg:Sr), eliminating the need for separate supplements for these elements.

Main advantages

• Concentrated ionic calcium powder — 5 g per 150 L increases calcium by 12 mg/L
• Non-caustic pH (8.3–8.6) — no risk of pH fluctuation unlike with kalkwasser
• Includes magnesium and strontium in typical usage ratios (100:5:0.1, Ca:Mg:Sr)
• Economical 500g format for medium to large aquariums
• Compatible with pre-mixed solution dosing pumps

Use in reef aquariums

Calcium is essential for the growth of all SPS and LPS corals, as well as coralline algae. If calcium becomes deficient, growth ceases and coral health declines rapidly. Reef Advantage Calcium differs from Kalkwasser in that it maintains a safe pH of 8.3–8.6 and simultaneously retains magnesium and strontium. 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 1 teaspoon (5 g) in 25–30 ml of water. According to Seachem, 165–200 g can be dissolved in 1 L of RO/DI water. Calculate the weekly amount based on the consumption rate and divide by 7 for the daily dosage.

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?

For complete reef supplementation, combine Seachem Reef Advantage Calcium with Seachem Reef Carbonate for alkalinity and Seachem Reef Advantage Magnesium for magnesium. Monitor your levels with the Salifert Calcium Test Kit or the Hanna Checker Calcium. For a secondary source of bioavailable organic calcium, add Seachem Reef Calcium.

Frequently Asked Questions

What is the difference between Reef Advantage Calcium and Reef Complete?

Both are Seachem ionic calcium supplements with magnesium and strontium in identical ratios. Reef Advantage Calcium is in powder form (more economical for larger volumes), while Reef Complete is in liquid form (easier to dose without pre-mixing).

Is a separate strontium supplement necessary with Reef Advantage Calcium?

No. Reef Advantage Calcium includes strontium and magnesium in proportions corresponding to typical usage rates (100:5:0.1, Ca:Mg:Sr). If used to maintain calcium levels, no additional strontium or magnesium supplementation is necessary.

Does Reef Advantage Calcium affect the pH of the aquarium?

No. The product mixes at a pH of 8.3–8.6, unlike kalkwasser which has a caustic pH that can cause dangerous fluctuations.