Calcium reactor

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In marine and reef aquariums, a calcium reactor is a device used to create a balance of akalinity in the system. An acidic solution is produced by injecting carbon dioxide into a chamber with salt water and calcium rich media. The carbon dioxide lowers the pH, dissolving the calcium media, and producing a solution high in carboxcylic acid. The effluent is then returned to the reef aquarium where it is used up by organisms, including corals. This is one of the most efficient ways of supplying calcium to a reef aquarium.

Contents 1 Reaction 2 Design and operation 2.1 CO2 Chamber 2.2 Bubble Counter 2.3 Feed Pump 2.4 pH Control 3 Trends 4 See also

[edit] Reaction

The objective is to dissolve the calcium laden media to provide both bicarbonates HCO₃^- (alkalinity) and calcium (Ca⁺⁺) ions at the sames rate as consumed during calcification. Effectively dissolving the media requires an acidic pH. Saltwater typically has a pH of at least 8.0, so to reduce the pH carbon dioxide (CO₂) is used. The general reaction form is:

CaCO₃ + H₂O + CO₂ <——> Ca²⁺ + 2HCO₃^-

[edit] Design and operation

[edit] CO₂ Chamber

Inside the reaction chamber, a calcium rich media, mainly CaCO₃, is forced into contact with water injected with carbonic acid (CO₂). This increases the solubility of the calcium carbonate. This reaction frees the calcium and carbonate, therefore supplying the aquarium with water rich in Ca²⁺ and CO₃^2-. These elements are important for maintianing both alkalinity and calcium levels.

[edit] Bubble Counter

The bubble counter is used to measure the rate of carbon dioxide introduced to the system. The flow rate of carbon dioxide must be monitored so that the maximum amount of gas disolves into the solution with a minimum left unconsumed. A needle valve is used to regulate the CO₂ bubble rate. Valves with precise adjusment abilities will improve bubble control characteristics.

[edit] Feed Pump

The feed pump controls the volume of water exchange in the system. This is important because a high rate of water flow into the reactor reduces it's efficiency, thus resulting in underproduction and a waste of CO₂.

A number of methods exist to supply the reactor with water from the tank. Some reactors siphon water into the input of the reactor's re-circulation pump. A potential complication is that the medium in the reactor may become compacted, increasing back pressure onto the pump and reducing water into the reactor. Placing a gate or needle valve on the reactor's outlet side will improve flow characteristics compared to control from the inlet side.

Alternately, peristaltic pumps are effective operating against pressure, capable of supplying a precisely adjustable and continuous flow over a varity of flow rates with minimal maintenance.

[edit] pH Control

The pH control adjusts the rate at which the calcium media dissolves. A control is connected to a probe in the reactor. When the pH goes above a certain level, a valve opens, allowing carbon dioxide to enter the reactor. It also closes the valve as the pH falls below this level.

[edit] Trends

[edit] See also

• Protein skimmer

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