Fluval BIO CO2 Diffuser

Fluval Bio-CO2 Diffuser disperses CO2 into your planted aquarium as an ultra-fine mist for maximum uptake by your plants. A high-quality ceramic disc breaks the gas into tiny bubbles that dissolve quickly, while the clear acrylic body stays discreet in the tank. It pairs with the low-pressure Fluval Bio-CO2 system (or a compatible low-pressure CO2 source) to give your plants the carbon they need for lush, healthy growth. German engineered, with two suction cups included. Choose the 125 for aquariums up to 125 L (33 US gal) or the 250 for aquariums up to 250 L (66 US gal).

Round out your planted-tank routine with plant supplements and browse our live aquarium plants.

Features

• Ceramic disc diffusion. A fine ceramic membrane turns CO2 into a micro-bubble mist for fast, efficient dissolving.
• Better plant absorption. Smaller bubbles linger in the water longer, so more CO2 reaches your plants.
• Clear acrylic body. Durable and low-profile, it blends into an aquascape.
• Easy mounting. Two suction cups hold it wherever your flow is strongest.
• German engineered. Precise, reliable diffusion built to last.
• Two sizes. Matched disc sizes for small and larger planted tanks.

Choose Your Size

How to Use

• Mount the diffuser in the lower half of the tank, in an area with strong water movement so the CO2 mist spreads evenly.
• Connect the inlet tube to your low-pressure CO2 source, such as the Fluval Bio-CO2 system.
• Run CO2 during daylight hours when your plants photosynthesize. It is not needed after lights-out.
• Rinse the ceramic disc every so often to keep the mist fine as mineral buildup collects.

Recommended Pairings

• Fluval Bio-CO2 Pro System: the low-pressure, fermentation-based CO2 source this diffuser is built for
• Plant supplements: liquid ferts to complete your planted-tank routine
• Live aquarium plants: the stems, carpets, and rhizome plants that thrive on added CO2

Frequently Asked Questions

Which size do I need?

Match the model to your tank volume. The 125 suits aquariums up to 125 L (33 US gal); the 250 handles up to 250 L (66 US gal) with a larger disc for more mist.

Do I still need a CO2 source?

Yes. This is the diffuser only. It connects to a low-pressure CO2 supply such as the Fluval Bio-CO2 system.

Freshwater or saltwater?

Freshwater planted tanks. CO2 injection feeds aquarium plants and is not used in reef or marine systems.

What comes in the box?

The clear acrylic ceramic-disc diffuser and two suction cups.