UP inline Standard CO2 and Super CO2 atomiser review


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If you're opting to go for a minimalist tank, these will truly float your boat reckons Nathan Hill.

Traditionally, CO2 diffusion has involved lengths of air line going into the aquarium, connected to atomisers. However, there are two downsides to these.

The first is their unsightliness and the second is the dispersal of their misted bubbles.

Anyone who has run one of these will be aware of the remorseful pang you feel as you watch most of your gas bubbling straight to the surface and disappearing into the air.

These inline diffusers get around that by producing a Venturi-style mist of CO2, ultra fine bubbles pushed around in the water flow — and often so small that their first instinct may not be to hurtle to the surface.

Either atomiser is designed to nestle between two lengths of return pipe coming from an external canister filter.

Threaded clamps hold them in place and then, depending on the model you have, either one or two ceramic diffusers inside the unit.

The 'two diffusers' format in the Super version is confusing, and I’m not sure I see the relevance.

The unit runs dry and so there’s no real need to diffuse CO2 into the chamber.

However, I have found that when cleaning the Super you can remove one diffuser while soaking the other in scale remover. Perhaps that’s why it’s the way it is.

Turn it all off, unscrew the top, pull out one of the ceramics, and get it cleaned while the other one bubbles away.

Alternatively, I note the bubble size varies according to which diffuser is used. When the small one is used alone, the bubbles appear considerably larger than when the larger diffuser is used.

Expect to start swearing when connecting these up for the first time, especially if working in a fiddly gap behind the tank.

The hose connectors don’t tighten without a considerable fight and, even then, you need to double check that everything is angled the way you want it.

You’ll also need high pressure to run either, starting at around 1.5 to 2 bar.

They are a pain to get the amount of bubbles just right, as any reaction from a change in regulator setting takes ages to have a knock-on effect on flow.

But for the aquascaper, they are excellent. The microbubbles they produce are difficult to see but, looking hard, you’ll see they’re all over the tank — in fact, anywhere there’s a water flow from the filter outlet, there’ll be CO2.

This is a very efficient way of getting gas into the tank.


The 'standard' model with just the one ceramic inside has proved to be my favourite, being easier to work with and, I think, better value for money.

However, I’d happily take either one over an in-tank diffuser.

Prices: Super atomiser £27.99, Standard atomiser £24.99. Available from tankscape.co.uk

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