FZONE Aquarium Inline CO2 Diffuser, L Size for 3/4-Inch Tubing with Replaceable Ceramic Diffuser

The FZONE Aquarium Inline CO2 Diffuser dissolves CO2 into aquarium filter outflow for planted tanks, with a replaceable ceramic diffuser and a size that fits 3/4-inch ID tubing.

• Up to 70% CO2 diffusion efficiency — helps dissolve CO2 into the water flow for plant absorption.
• External, inline installation — keeps diffuser equipment out of the aquarium and leaves more open tank space.
• Distribution through filter outflow — spreads CO2 across the aquarium and helps reduce dead spots.
• Aluminum alloy body and replaceable ceramic diffuser — combines a corrosion-resistant body with a replaceable bubble-producing component.
• Tool-free push-fit connections with hose-locking nuts — makes installation and removal straightforward while helping prevent leaks.

Planted aquariums need CO2 dispersed through the water so it can reach plants around the tank. This inline design puts the diffuser on the filter’s outflow rather than inside the aquarium, making it suited to setups where an uncluttered interior and broad water-flow coverage matter. Its distribution approach is particularly suited to medium and large aquariums, including systems with powerful filter flow.

Which tubing size does this FZONE inline CO2 diffuser fit?

This FZONE Aquarium Inline CO2 Diffuser fits 3/4-inch ID tubing and corresponds to the L size, with a 20 mm diffuser size. FZONE’s size range also includes S for 1/2-inch ID tubing and M for 5/8-inch ID tubing. Match the tubing’s inside diameter to the correct size before installation.

• S: 13 mm diffuser size for 1/2-inch ID tubing.
• M: 17 mm diffuser size for 5/8-inch ID tubing.
• L: 20 mm diffuser size for 3/4-inch ID tubing.

How does the FZONE diffuser distribute CO2?

The FZONE Aquarium Inline CO2 Diffuser introduces CO2 into the filter’s outflow, carrying it through the aquarium with the moving water. Its replaceable ceramic diffuser produces bubbles smaller than 0.1 mm, creating a fine mist to support CO2 dissolution and plant absorption. The outflow-based approach is designed to cover medium to large aquariums and help reduce areas with less CO2 circulation.

• Requires a working pressure of at least 30 psi.
• Designed for use with aquarium filter outflow.

How is the FZONE inline diffuser installed and maintained?

The FZONE Aquarium Inline CO2 Diffuser connects into the filter outflow with a quick-connect push-fit system, so installation and removal do not require tools. Hose-locking nuts secure the connections and help prevent leaks. The ceramic diffuser is replaceable, while the aluminum alloy body is corrosion resistant.

• Mounts externally on the filter’s outflow pipe.
• Replaceable ceramic diffuser component.

This diffuser suits planted-aquarium owners who want CO2 carried through filter outflow, especially in medium to large tanks where broad distribution is useful. It is the L-size option for 3/4-inch ID tubing, with an external design that keeps diffuser equipment out of the tank.

Read our guide: Aquascaping a freshwater tank: substrate, stone, wood and light