Calcium reactor

Lore & Background

The calcium reactor operates by forcing calcium-rich media, typically aragonite, into contact with water injected with carbon dioxide to create carbonic acid, increasing solubility. The reaction frees calcium and carbonate, supplying the aquarium with water rich in Ca2+ and CO2−3. A bubble counter visually or audibly measures the CO2 rate, and a needle valve or solenoid valve regulates the bubble rate. A feed pump controls water exchange volume, as high flow can reduce efficiency and waste CO2. Some reactors siphon water into the recirculation pump input, but media compaction can increase back pressure; placing a gate or needle valve on the outlet side improves flow. Peristaltic pumps are effective against pressure and provide adjustable continuous flow with minimal maintenance.

Reader's Guide

A pH controller is recommended to control CO2 by measuring the reactor's pH via a probe and turning the CO2 flow on or off. The typical pH range inside the reactor is 6.5 to 6.8. Some pH controllers have an interface for an air pump connected to an airstone in the sump or main tank; if the probe detects low pH, the pump activates and bubbles raise pH by dissipating CO2 gas. Since the reactor's pH is much lower than the aquarium's, running a calcium reactor risks lowering aquarium pH. To counteract this, many manufacturers offer reactors with secondary buffering chambers filled with the same media but without CO2 injection; the effluent passes through this chamber, consuming excess CO2 and raising the solution's pH before entering the aquarium. The reactor dissolves media to provide bicarbonates and calcium ions at the same rate as consumed during calcification.

Did You Know?

• The reaction formula inside a calcium reactor is CaCO3 + H2O + CO2 ⇌ Ca2+ + 2 HCO−3.
• A pH controller can turn CO2 flow on and off based on the pH inside the reactor, typically set between 6.5 and 6.8.
• Some calcium reactors include a secondary buffering chamber filled with the same media but without CO2 injection to raise the effluent pH.
• Peristaltic pumps are effective for supplying adjustable and continuous flow against pressure with minimal maintenance.