Addign CO2: needle wheel methods

Tom Barr

Staff member
Jan 23, 2005
I've been playing with CO2 for 20+ years as some may know.
Venturis where one of the last incarnations into adding CO2 to planted tanks, this was merely taken from marine systems and larger scale aquaculture use, no new info really there other than it works amazingly well.

But the trade off and one reason why it worked so well was due to the increase of flow rate between the water mixed and the gas.

If you run 100gph through a reactor and 500 gph, which will have a better response time in 100 gallon tank?

The answer should be obvious.

The same is true for CO2 mist.
The aquarium is the reaction chamber essentially.

Needle wheels are hardly my invention.
We have bubbles CO2 into intakes of pumps for years and cansiter filters intake do this as well.

However, modification of the impeller to create a needle wheel dramatically improves the misting effect.

Unlike Venturis, does not impede flow rates nor require any added pressure and is simple to size.

They can be used in line, externally and internally.

The cost is about 10-60$ depending on the size of powerhead/pump you chose really for anything 180 gal or less.

Here's some threads on DIY impellers from marine sites.

Many folks in the FW plant area have simply take a hot needle and poked holes, alternating back and forth to each impeller blade, this adds more turbulance and chops the CO2 bubbles up even better.
You can use the scrub pads as well, they will work better but produce less flow out the end of the powerhead.

You can buy needle wheel powerheads also, and impellers.
I'd suggest giving this a try, if you have an internal reactor, this will help to get rid of them all, and go with simply a modified powerhead, which is not that unattractive compared to a tube and a powerhead.

If you slip a tube from the suction side out of the tank and to an external pump with a mod impeller, then you have an external needle wheel, simply put a small air line tube or hole to suck the air out to start the siphon. Then fire it up and put the return back into the tank.


In line, same type of thing as above, just Tee of the main line and add ball valves to control the flow, make a hole on the suction side for CO2 and add a check valve. Then the pump will such the water from the main line without reducing any flow(your suction should increase a bit and end up with a slight higher flow rate, quite unlike a Rector or Venturi!)

Hope this helps,

Tom Barr