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Re: [APD] CO2 mist

> Date: Wed, 15 Mar 2006 21:40:20 -0800
> From: "Joel Fizette" <sentientpuppet at gmail_com>
> Subject: [APD] Co2 mist
> To: "aquatic plants digest" <aquatic-plants at actwin_com>
> I'm having trouble finding info on this "co2 mist" people keep
> talking about
> I've found hundreds of postings in the archives and can't seem
> to figure out
> how exactly it's produced... can someone point me in the right
> direction?

The method is simple: Take a fine diffuser stone(limewood or the
Sweetwater ones from Aquatic Eco are okay but you have to order
them etc) and place the mist eminating from this next to the
current so the mist gets blasted all around the tank and hits
the plant leaves. 

Some have used powerheads connected to a spray bar and fed the
CO2 into the intake side of the powerhead and this produces good
even mist along the back wall of larger tank sizes.

ADA tanks often use a similar approach. 

I think I'm the only person that has used Fick's law of
diffusion to suggest that this mist is superior to dissolved CO2
in water.
It's not an all or nothing thing either.
Some of the mist does dissolve, some does not.
How much is hard to say directly.

But if you look at Fick's first law of diffusion, it would
appear that for each parameter, the gas phase has far better
characteristics than a liquid phase and can fully maximize the
photosynthetic capacity of submersed plants.

Concentration-> gas bubbles will have a higher
concentration(even if you lost 99% of the CO2 in the first 30
seconds, it's still 10,000 ppm)

Diffusivity coefficent, it's 10,000 times high for the gas than
the liquid(H20).

Distance, the gas can hit the plant directly reducing the
distnace for transfer

The first two are the main players.
Even if you believe that dissolved CO2 is the only way to go,
adding the mist on top of that, will only add even more wiggle
room to your CO2 dosing method, something folks might want to
really consider.

Folks that have actually tried it and had decent plant biomass,
dosing, light etc found a dramatic increase in pearling.
Many complained about all the pearling, all the plant growth and
other related issues(lack of algae etc).

Try a limewood stone placed under the filter flow and direct the
mist into the plant beds as evenly as you can.
Turn CO2 off at night also. You can add more CO2 safely and in
conjuction with high O2 levels by doing this. This is better for
bacteria and fish or at the very least, gives them a break from
high CO2/low O2.

Tom Barr 


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