Efficacy of CO2 absorbtion into WC


Prolific Poster
Jan 28, 2007
I'm pokin around with making a new reactor for one of my tanks. I was wondering how to make it as efficient as possible.
The thing that occurred to me that might be really efficient, is the possibility of atomizing or finely misting WC into a chamber that is filled with CO2. The fine water droplets would have significant surface area and would be exposed to high if not pure ambient CO2 and would collect and flow out re-entering aquarium.
Question is would this be effective if built on a scale to accommodate adequate volume of misted water?
Another thing that occurs to me as that this may also cause off gassing of nitrogen and oxygen in the WC as it is misted which would accumulate in the misting chamber. I guess I would need the chamber to purge occasionally.
Does this sound like good idea?
More or less effective than what we already have available to us?
Problems I'm overlooking regarding concept?


Lifetime Charter Member
Lifetime Member
Jan 15, 2009
It might work, although I suspect pressurizing the chamber with CO2 might work better but then you risk having your outflow fizz a bit.

Having said that, CO2 is relatively cheap. To get a really good water mist you are probably going to need a high pressure pump to get this to work. I mean something like the downdraft skimmer pumps the reefers use. The electrical costs of running this ( not to mention the pump cost ) will probably far outstrip any economical efficiency you get from the CO2 use reduction ( assuming it works the way you hope it will ). From an environmental standpoint you're likely to use MORE resources to run the pump and such than the "cost" of using a little more CO2. That's strictly conjecture on my side, but if the choice to do this is environmentally driven you should at least consider it since you're going to have to buy the CO2 anyway.

I would imagine the best was is one of the inline reactors. Low bubble count and any bubbles swirl around inside until the CO2 dissolves. You might be able to get some sort of spray nozzle in there, but a jet of water blasting down from the top to mix up the CO2/water into a froth should do the same thing. This is pretty much what a downdraft skimmer does.

For an experiment, you could get two small tanks and on one you use your design, and the other just use one of the inline reactors. Tom's inline/external design seems to work pretty well from all accounts so that could be a useful baseline. Try to get similar/identical flow in the tanks if possible and put a drop checker in each. Time the color changes. Not overly scientific, but at least you'll have a baseline.


Tom Barr

Staff member
Jan 23, 2005
If you do a large WC, then the plants are already exposed to the air, gas phase CO2.

So they can nab all they want real fast, I do the WC's about 1 hour after the lights come on in the morning.

They are ready taking up lots of CO2 by then due to light, this pushed them even faster.

Then I refill and they pearling like mad.

Tom Barr


Prolific Poster
Jan 28, 2007
Sorry for any ambiguity in my use of the acronym "WC" Tom. Rather than water change I was referring to water column.
Thanks for the suggestions Shog..., I have already designed the system, and there really is no loss to speak of except for the potential need for a purge cycle periodically to clear the chamber of O2 that may off gas during misting, but that may not even be necessary.
As far as energy consumption goes, small misting pumps do not use much juice but my intention is not to conserve CO2 so much as to possibly devise a more effective means of providing consistent, responsive levels of CO2 in the water column.
My question really is would water misted into a CO2 filled chamber absorb CO2 into solution quicker and at a higher degree of saturation than water flowing through a reactor with bubbles of CO2 bouncing around in the chamber?