I usually difuse the CO2 by using a powerhead and hooking up the CO2 line in the suction so the bubbles get broken by the powerhead impeller and then fly along the tank. I have such a setup in my 6 ft. tank and tiny bubbles fly from one side to the other with no problem. The efficiency of that method is great - on my 180 gal. tank a 10 lb. CO2 bottle lasted for 3-1/2 months!

The sight of fine bubbles flying all over the tank is not something I completely enjoy. But I know that CO2 is getting everywhere so I tolerate it.

Today I tried something a little different. I know someone else has done it before but the efficiency of the setup really amazed me.

I placed a sponge on the powerhead outflow:


1. Powerhead
2. Sponge
3. CO2 line
4. Suction of water + CO2
5. Coarse pre-filter (so snails don't end up sucked, dying and clogging the suction of the powerhead)

The efficiency of that simple setup is amazing. I can see the bubbles going into the powerhead because the CO2 line that I use is clear. I can also hear the bubbles hitting the powerhead impeller. 1 bubble per second definitely goes goes into the powerhead.

After about 12 hours of work the sponge was covered with bubbles that stay embedded inside the pores. A lot of dust-like bubbles leave the sponge but nowhere near the CO2 loss of a regular diffusor (atomizer). The bubbles are really small - you can't see the bubbles from 4 ft. away. There are no bubbles accumulating in the sponge. With 1 bubble per second and a 200 GPH powerhead there are almost no bubbles that remain undisolved. I'd say the efficiency of that simple set-up is close to 99%.

The diffusor has been working perfectly since I set it up. No fertilizers have been added to the tank yet but the plants are pearling very heavy under 2 wpg of light. Strings of Oxygen bubbles from the valisnerias are all over and big (1/4") bubbles from the wide leafed L. ovalis float up every 2-3 min.

The tiny bubbles that the powerhead's impeller produces get stuck in the sponge and the 200 GPH flow has time to disolve them. Only a small amount of CO2 makes it outside of the sponge. The small bubbles raise very slowly to the surface and have even more time to disolve.

I dislike the sight of equipment in the tank but for a quick and simple solution that combination seems to be great. Especially if used with a DIY yeast CO2 reactor.

--Nikolay

I have a very similar setup like yours Niko, but instead of inserting the co2 tube near the intake, I connect it to a glass diffusers that is place directly under the intakes. The diffuser is surrounded by a outer sponge layer to keep the diffuser in place. Not only does it works well, but even smaller bubbles are produce making it more efficient.

That is a great idea NIKO to put a sponge over the out let,I am trying to replace my DIY external reactor ,with a RIO RVT pump but the problem is that the bubbles are still too big so I thought of feeding the outlet of this pump to the inlet of the Maxi jet.I haven't done it yet but after seeing your idea of using a sponge on the outlet,maybe I'll give that a try.
One question :don't you think you would disperse the dissolved co2 better by putting a pump in front of the sponge?just a thought.

Well, according to Mr. Barr and a few others, CO2 micro bubbles are better than dissolved CO2, even though there is no concrete proof. The theory is that 30 ppm CO2 in water is not as good as CO2 bubbles on leaves (2000ppm). Did you just observe the opposite?

If you are posing this question to me,I fully dig Mr Barr
The reason I suggested a second power head is he already made the choice to dissolve the co2,I say now that you got it, why not put a power head to distribute it better .
I have two reactor in a 6' long tank one is by a power head mist and the other is an external one which I will retire in favour of another mist reactor.
I don't mind micro bubbles floating around the tank at all .here is a link that describes the whole situation:

mist or reactor - Barr Report

Aquadise,

I have a set-up with a powerhead above a Dupla CO2 atomizer. It works well - the small bubbles from the atomizer get broken into even smaller ones by the powerhead's impeller. But as I said the microbubbles flowing all over the tank is something I don't like.


Distrbd,

I spraybar could be placed above the sponge and will disperse the tiny bubbles that come out of the sponge. But for now, for me, it all seems to work fine as it is.

One detail - at the end of the CO2-tubing I have stuck a piece of bamboo chopstick. It produces very small bubbles by itself. So in the "sponge reactor" on the picture the CO2 bubbles come out of the tubing already small, then the impeller chops them up, then they get blasted around inside the sponge center opening, then they get stuck in the sponge itself with water flowing around them, and finally the ones that escape are too small to raise fast to the surface.

--Nikolay

Actually there is "proof", I'd prefer to call it "solid evidence".
It's called a dissolved O2 meter.

Control: tank with reactor that dissolves the gas 100%: add 30ppm of CO2 or slightly more

Take a tank with mist, measure the dissolved CO2 accurately(target 30ppm dissolved).


You can use the same tank but the order of the control/treatment is important: do the Reactor (no mist) control after the mist method. You should not prune the plants in between.

This difference in time between treatments will produce more plant biomass(and thus higher O2 levels as well) for the control test tank.

So you skew the O2 levels to the control.

Allow the tank to grow well for 1-2 weeks prior.
Maintain good light/Nutrients/water changes etc.

Do the mist for 2 days and measure the O2 at various times
Do the control for 2 days after the mist and measure the O2 at the same times as the control.

Maintain similar dissolved CO2 levels or a little higher in the control tank.
This will also skew a higher O2 level towards the control.

Even with the skewing, I found on average of 3 runs, 10-40% higher levels of O2 for each time data point.

Now if there was no effect, I should see equal or less.

Unlike watching pearling, O2 meters are quantifying the production by the plants, this production is growth.
And the pearling is only measured by O2 levels, not any other gases.

And O2 meters have temp compensation ATC (the tank changed 3F with the lights on over the day).

So explain that.
Sounds like the higher O2 is a direct result of the mist effect.


Regards,
Tom Barr

Why not use the plant's themselves as the surface for the bubbles to stick to instead of a sponge?

Specifically their lower abaxial sides where the stomates are?

Regards,
Tom Barr

Personal preference.

Perceived water clarity. The tank doesn't look serene but turbulent with all the bubbles flying around.

Compare a tank with no bubbles and completely "missing" water and one with bubbles all over and plants pearling madly.

The original post was about a quick, simple and dirty way of disolving CO2 well. Any equipment in the tank is ugly, including beautiful lilly pipes.

--Nikolay