CO2 pH Controller

A CO2 pH controller automates planted aquarium CO2 management by continuously monitoring the pH of the aquarium water and switching CO2 injection on or off to maintain a user-programmed target pH level. Because dissolved CO2 acidifies aquarium water, maintaining a stable pH setpoint serves as an indirect proxy for maintaining stable CO2 concentration. The controller includes a pH electrode probe, a digital LCD display showing current pH and setpoint, and a relay output that connects to a CO2 solenoid valve. When pH rises above the setpoint, CO2 injection is triggered; when pH reaches the target, CO2 is cut. This provides precise and responsive CO2 management superior to a simple timer, and is especially valuable in high-demand planted tanks with fluctuating plant uptake rates.