Dennerle CO2 Diffusor Ultra, Small

Ceramic Disc CO2 Diffusor for Planted Tanks Up to 100 Liters

The Dennerle CO2 Diffusor Ultra (100L) is a compact CO2 diffuser for freshwater planted tanks rated up to 100 liters (~26 gallons). It is a diffuser accessory, not a complete CO2 system — it connects to an existing CO2 source such as a pressurized cylinder with a regulator or a BIO CO2 system, and converts the CO2 supply into fine bubbles that dissolve efficiently into the water column before reaching the surface.

The ceramic disc atomization is the most functionally important specification on this product. Fine bubbles produced by a high-quality ceramic disc have more surface area per unit of CO2 than coarse bubbles, giving each bubble more time to dissolve before escaping at the surface. That translates directly into better CO2 efficiency per bubble — less wasted gas and more CO2 actually available to plants. The shatterproof acrylic body replaces the glass construction common in lower-cost diffusers, eliminating the most common failure point in a CO2 diffuser setup. The built-in bubble counter lets you monitor CO2 delivery rate without installing a separate in-line bubble counter. CO2 hose with 4mm inner diameter (6mm outer) is included.

Key Features:

• Ceramic disc produces fine CO2 bubbles for efficient dissolution into the planted tank water column
• Shatterproof acrylic construction; more durable than glass diffusers without visual compromise
• Built-in bubble counter for monitoring CO2 bubble rate without a separate in-line counter
• Includes CO2 hose with 4mm inner diameter / 6mm outer diameter — standard CO2 system sizing
• Compact and clean design suited to aquascape setups where visible equipment affects the layout
• Rated for freshwater planted tanks up to 100 liters (~26 gallons)
• Requires a separate CO2 source: pressurized cylinder with regulator, or BIO CO2 system

Ideal For:

• Nano and small planted tanks of 10 to 26 gallons running a pressurized or BIO CO2 system where a compact diffuser that does not visually dominate the layout is needed
• First-time CO2 system builders adding a diffuser to a small planted aquascape as the final component of their CO2 setup
• Aquascape hobbyists running a Nature Aquarium or Dutch style layout in a desktop or mid-size tank who want fine-bubble CO2 delivery with a clean, low-profile diffuser

Pro Tips:

• Position the diffuser near the filter intake. Placing the diffuser close to the intake of a canister or HOB filter pulls CO2 bubbles into the filter and distributes dissolved CO2 evenly throughout the tank. This is more efficient than placing the diffuser in a low-flow corner where bubbles rise undisturbed to the surface.
• Start with a low bubble rate and dial up slowly. For a 100L tank, begin at one to two bubbles per second and increase gradually over several days while monitoring plant response and fish behavior. Signs of CO2 oversupply include fish gasping at the surface; signs of undersupply include slow plant growth and algae on leaves.
• Clean the ceramic disc every four to six weeks to maintain fine bubble output. Calcium and algae buildup on the ceramic disc reduces bubble fineness over time. A brief soak in diluted citric acid or white vinegar, followed by a thorough rinse with clean water, restores the disc's atomization quality.

Online exclusive: this item is ordered in for you and is usually ready within a few business days. Choose in-store pickup, local delivery or shipping at checkout.