Week Aqua Inline CO2 Diffuser

Invisible CO2 dosing for serious aquascapes

If you run an external canister filter, the Week Aqua Inline CO2 Atomizer is the cleanest way to inject CO2 into your planted tank. Instead of mounting a glass diffuser inside the aquarium — which steals visual space from your scape and accumulates algae — the atomizer sits hidden in your filter’s outflow tubing, behind or under the cabinet. The result is a noticeably cleaner aquascape with no in-tank hardware, paired with significantly higher CO2 dissolution efficiency.

How an inline atomizer works

CO2 from your regulator enters the atomizer through a dedicated quick-plug fitting. Inside the chamber, the gas is forced through a cylindrical ceramic atomizing core under pressure — breaking it into a fine mist of micro-bubbles. The powerful flow from your canister filter then carries this mist through the outflow tube and into the tank, where the bubbles dissolve almost instantly into the water column. Compared to a standard in-tank glass diffuser, more of the CO2 you pay for ends up actually fertilising your plants.

Key features

• Quick-plug fittings — the CO2 line and water tubing lock in securely; no worrying about tubes popping off under pressure
• Durable metal body — crack-resistant, built to last through repeated cleaning cycles
• Cylindrical ceramic atomizing core — produces an exceptionally fine mist for near-complete CO2 dissolution
• Three tubing sizes available — 12/16mm (13mm), 16/22mm (17mm), and 20/22mm (19mm) to match all popular canister filter brands including Eheim, Fluval, Sunsun, and Oase
• Compact form factor — fits easily inside most cabinet setups without modification to your plumbing

Which size do I need?

Match the atomizer to the tubing diameter your canister filter uses, not the filter model. The number refers to the inside diameter / outside diameter of the hose. Most mid-sized canister filters (rated for 200–400L tanks) ship with 16/22mm tubing. Smaller filters and aquascape-grade setups often use 12/16mm. Larger setups using filters like the Fluval FX series, Eheim Pro 4+ 600, or Sunsun HW-5000 typically use 20/22mm tubing.

Installation

Cut the outflow tubing of your canister filter at a convenient point — ideally outside the tank, between the filter and the lily pipe or return outlet. Push both cut ends firmly into the quick-plug connections on the atomizer. Connect your CO2 line from the regulator to the dedicated CO2 inlet. Run the filter and check carefully for water leaks before turning on CO2. Only connect the atomizer to the outflow side of your canister — never the intake — to avoid trapping CO2 bubbles inside the filter motor.

Important usage notes

• Minimum 30 psi working pressure required. The ceramic core needs sufficient back-pressure to atomise CO2 properly. This product is not suitable for bio-CO2 systems running yeast fermentation — pressurised cylinder setups only.
• Use CO2-rated pressure-resistant tubing only. Standard silicone airline tubing will rupture under the pressure this atomizer requires. Always use acid-resistant, pressure-rated CO2 tubing.
• Soak the ceramic core in water for 30 minutes before first use. A dry ceramic membrane will not atomise efficiently and may produce large bubbles for the first few hours of operation.
• Clean by soaking only — never scrub the ceramic. If micro-bubble output drops over time, disassemble and soak the ceramic core in a 1:3 mix of bleach and water for an hour, rinse thoroughly, and reinstall.

What’s in the box

• 1 × Week Aqua Inline CO2 Atomizer (size of your choice)
• Quick-plug fittings pre-installed
• Replaceable ceramic atomizing core

Manufactured by Zhuhai Weekaqua Technology Co., Ltd. — the same company behind Week Aqua’s popular P-series aquarium LED lights and CO2 regulator range.