Seachem Reef Strontium 250 mL — Strontium Gluconate for Reef Aquarium

Seachem Reef Strontium 250 mL is a concentrated strontium supplement in gluconate complex form, formulated to restore and maintain strontium levels at natural seawater levels in reef aquariums. In the ocean, strontium is present at a concentration of 8 to 12 mg/L—chemically very similar to calcium, it is incorporated directly into the calcareous skeleton of corals, coralline algae, and bivalve mollusks along with calcium. In an aquarium with a high concentration of hard corals, these levels drop rapidly and inhibit calcification even when calcium and alkalinity are perfectly maintained.

The 250 mL format is ideal for small to medium-sized aquariums, or as a starter format to test the protocol before moving on to 500 mL.

Gluconate Technology — Why It Changes Everything

Reef Strontium uses gluconate complexation — the same technology as Reef Calcium — which provides three decisive advantages over simple ionic strontium:

• Increased bioavailability: gluconate keeps strontium in solution and facilitates its direct absorption by the calcifying tissues of corals
• Source of metabolic energy: gluconate itself constitutes an organic fuel directly usable by corals to support their growth.
• Inhibition of precipitation: the gluconate complex prevents strontium from precipitating and depleting alkalinity — a common problem with uncomplexed ionic supplements

The product is formulated at 10,000 mg/L —a high concentration that allows for effective dosing with small volumes. It is nitrate- and phosphate-free, and nitrogen-free. The gluconate formula is biologically ineffective in promoting the growth of unwanted algae.

Who Benefits from Strontium

Reef Strontium is particularly useful in aquariums with a high density of:

• Hard corals (SPS and LPS): intense calcification continuously consumes strontium
• Coralline algae: their development depends directly on the levels of available strontium.
• Tridacna clams: their rapid growth depletes strontium and calcium faster than most other organisms
• Systems without regular water changes: strontium is not naturally replenished in closed systems.

Note: If you are already using Reef Complete or Reef Advantage Calcium which already contain strontium in their Ca:Mg:Sr ratios, Reef Strontium becomes necessary only in very high density or intensive calcification systems.

Seachem Official Usage Protocol

• Maintenance dosage: 5 mL (1 capful) per 80 liters, twice a week
• Target level: 8–12 mg/L — test with Reef Status™ Strontium
• Increase: Each 5 mL/80 L dose raises strontium by approximately 0.6 mg/L — adjust frequency or dose according to test results
• Caution: Do not mix directly with carbonated (alkalinity) supplements. Alternate doses or wait at least 30 minutes between the two.
• Storage: No refrigeration required

Yield of the 250 mL format

• 200-litre aquarium: approximately 12 weeks at a rate of 2x/week (standard dose)
• 400-litre aquarium: approximately 6 weeks at a rate of 2x/week