Understanding the CO2 Regulator and Planted Tank Relationship

Carbon dioxide is a chemical compound composed of two oxygen atoms bonded to a single carbon atom (O=C=O). During photosynthesis, terrestrial and aquatic plants use carbon dioxide and water, removed from the atmosphere and combined with light energy to produce oxygen and sugars. These sugars may then be consumed in respiration or used to produce polysaccharides, complex carbohydrates, such as starch, cellulose, proteins, and other organic compounds required for plant growth and development.

In the planted aquarium ecosystem, carbon dioxide is introduced through the use of a  CO2 regulator in combination with additional equipment. Carbon Dioxide (CO2) is fundamental to the function and success of the planted tank. 

CO2 Cylinder – Carbon dioxide (CO2) in a cylinder exists primarily in the form of liquid CO2, only the head space of the tank contains gas. The liquid allows the cylinder to maintain a constant and high pressure; as long as the cylinder contains any amount of the liquid CO2 the regulator’s high pressure gauge will read full, between 800 – 1000 PSI.

CO2 Pressure Regulator – designed to reduce the high pressure inside of a CO2 cylinder to a lower, usable pressure that can be dispensed. The pressure-reducing regulator takes a pressure of 800-1000 PSI (pounds per square inch) from the cylinder, and regulates it, providing a controlled, reduced pressure output in the range of 1-40 PSI. Our CO2 regulators have CGA (Compressed Gas Association) 320 fittings for USA and Canada. 

High Pressure Gauge – located at the nine o’clock position, it reads the amount of pressure present in the cylinder. As long as there is liquid gas in the cylinder the pressure will read at or around 800 – 1000psi. For CO2 cylinders, once the gauge reads in the red, the liquid gas is depleted and the cylinder should be refilled. 

Low Pressure Gauge – located at the twelve o’clock position, it represents the working pressure or output pressure; the pressure you are using, which can be adjusted.

Adjustment Screw – Adjustments to the output pressure (read on the low pressure gauge) are made with the adjustment screw or t-handle located in the center of the regulator body. The output pressure is set by turning the screw clockwise to increase the output pressure. To reduce the output pressure, the screw should be turned completely counter-clockwise.

Tank Connector Nut – attaches the regulator to the cylinder. Due to high pressure in the cylinder, this connection is a common location for leaks; it is critical to securely fasten the connector nut using the correct seal, nylon or permaseal. The connection must be tightened with a crescent wrench or CO2 wrench.

Solenoid Valve – the solenoid valve is an electromechanical device that controls the flow of CO2 gas from the regulator to the aquarium. The solenoid should be connected to a timer or pH controller to control the output of CO2 into the aquarium. It is the on / off valve. 

Pressure Relief Valve– functions to release excess pressure in the regulator.

Needle Valve – the needle valve provides precise control over the amount of CO2 allowed to enter the aquarium. It allows you to fine tune and regulate the rate of flow, the number of CO2 bubbles per second.  It is important to invest in a quality needle valve for increased precision and to avoid the potentially negative effects of “end of tank dumps”. As the liquid gas in a cylinder nears empty, the pressure in the cylinder will decrease, causing the output pressure to quickly increase and potentially “dump” out of the cylinder into the aquarium. A needle valve will control this “dump” because it functions as the gateway that controls the volume of gas entering the aquarium, it will stabilize the increased output pressure at the set rate of flow (bubbles per second) preventing the CO2 from completely dumping into the aquarium.

Bubble Counter – a visual tool in measuring the number of bubbles per second entering the aquarium. A bubble counter allows you to count the exact number of bubbles per second so that fine adjustments can be made to the rate of flow.