Reef Reactor Lg 4 L — High Purity Aragonite 1–3 cm Calcium Reactor | Seachem

Seachem Reef Reactor Lg 4 L is a high-purity aragonite media designed for calcium reactors in reef aquariums. With a grain size of 1–3 cm, the Lg format dissolves more slowly than Md (0.5–1 cm), providing a prolonged and more stable release of essential elements. By dissolving under the action of CO2 in the reactor, it supplies calcium, magnesium, strontium, potassium, and carbonates for optimal growth of corals and calcareous organisms.

Main advantages

• High-purity aragonite — a natural and balanced source of calcium, magnesium, strontium, potassium, and carbonates
• Particle size 1–3 cm (Lg) — slower and more stable dissolution than the Md format (0.5–1 cm)
• Highest level of soluble potassium of all competing brands
• Lower levels of aluminum and phosphorus than any competing brand
• Stabilizes alkalinity and pH — promotes rapid coral skeleton formation

Use in calcium reactors

Rinse the Reef Reactor before first use in the reactor. The water flow rate through the reactor, combined with the pH of the water inside the reactor, controls the media dissolution rate. Follow the calcium reactor manufacturer's instructions and adjust the water flow rates and CO2 injection to achieve the desired calcium and alkalinity concentrations in the effluent. Maintain calcium between 380–420 mg/L and alkalinity between 3–6 meq/L (8–17 dKH).

Lg vs Md — Which particle size to choose

• Reef Reactor Lg (1–3 cm): Slower and more uniform dissolution. Recommended for large reactors and systems requiring extended stability between refills.
• Reef Reactor Md (0.5–1 cm): faster dissolution. Recommended for small reactors or systems with high calcium demand.
• The two formats can be mixed in the same reactor to adjust the dissolution rate.

Items provided

• Calcium — growth of the coral skeleton
• Magnesium — stabilizes calcium in solution
• Strontium — growth of SPS and LPS hard corals
• Potassium — coral colour and health (highest soluble level on the market)
• Carbonates — alkalinity and pH stability

Available formats

• Reef Reactor Lg: 2 L, 4 L
• Reef Reactor Md: 2 L, 4 L

Why choose the Reef Reactor from ReefSolution?

The Reef Reactor Lg 4 L is the economical size for large calcium reactors. For smaller reactors or faster dissolution, the Seachem Reef Reactor Md is available. Use Seachem Reef Status Calcium and Seachem Reef Status Magnesium to monitor your parameters. For manual dosing in addition to the reactor, Seachem Reef Advantage Calcium and Seachem Reef Carbonate are recommended.

Frequently Asked Questions

What is the difference between the Reef Reactor Lg and the Md?

Particle size: Lg is 1–3 cm and dissolves more slowly, Md is 0.5–1 cm and dissolves more quickly. Lg offers longer stability between refills, while Md is suitable for systems with high calcium demand.

Can the Reef Reactor be used without a calcium reactor?

No. The Reef Reactor is specifically designed to be dissolved by CO2 in a calcium reactor. For dosing without a reactor, use Seachem Reef Fusion 1 and 2 or Seachem Reef Advantage Calcium.

How often should the media in the reactor be replaced?

When the media volume has decreased significantly due to dissolution. The frequency depends on your system's calcium demand and CO2 flow rate. Monitor calcium and alkalinity levels in the effluent to determine when to recharge.