CO2 Bubble Counter with Check Valve

This combination CO2 bubble counter and integrated check valve provides two essential functions in a single inline component. The acrylic bubble counter chamber allows real-time visual monitoring of CO2 injection rate, while the built-in check valve prevents aquarium water from back-siphoning into the CO2 line when pressure drops — such as when the solenoid closes at lights-out or the cylinder is changed. Without a check valve, water drawn into the CO2 tubing can cause blockages, damage the needle valve seat, or in severe cases reach the solenoid or regulator. This combined unit reduces the number of fittings required in the CO2 line and is suitable for all planted aquarium CO2 setups using standard 4mm CO2 tubing.