CO2 mist idea....

[Lonewolfblue]

Here's an idea on a system for CO2 mist in a tank. This is for a 75G, 48" long.

On the right, the blue is my XP3 intake.

On the left, the blue is my XP3 spraybar.

The powerheads will be the Aquaclear Powerheads with the quickfilter attachment on each. The CO2 will be injected into the Quickfilter. Inside the quickfilter will be either a limewood airstone, or other fine output airstone. The fine bubbles will be taken directly into the powerhead, down the tubing, and out the spraybar at the bottom of the tank.

The spraybar will have holes pointed straight out, and a few at a 30 degree angle up. The amount of holes and size of holes will be at the right size so there will not be a lot of current, but a nice mist of CO2 going up through all the plants without a powerhead waving the plants all over the place. It will also be placed at the substrate level, hidden by all the plants unless you have a hole where you can see the back of the tank.

What are your thoughts on this?

[evercl92]

interesting idea. I'm curious to find out if the CO2 will disperse evenly across the spray bar or if it will output only part way across.

[Lonewolfblue]

Originally Posted by evercl92

interesting idea. I'm curious to find out if the CO2 will disperse evenly across the spray bar or if it will output only part way across.

That's why I had the idea of powerheads on both sides. I was also playing with the idea of cutting the spraybar in half, and closing off the ends and having 1 powerhead run each. Each spraybar would then only be 18-20 inches long.

Another idea that was brought up to me was placing the airstones at the base of each tube at the intake of the spraybar. That may help in not having near as much CO2 buildup in the tube going to the bottom.

Also, another reason for using the Quickfilters is they can be used to clean the water before going into the system. They are very fine filters, and can act as a partial diatom filtering system that runs all the time. It's not really a diatom filter, but the cartriges do an excellent job of removing a lot of very fine particles. Then for maintenance, you just unplug the powerheads, pull off the quickfilters, replace with new, and put back on. No need to remove the powerheads themselves or disconnect any tubing or the spraybar.

[7Enigma]

I like the idea. I originally thought you had the PH's injecting the CO2 at/near the surface and thought that might not be a great idea. But now I see you are using the PH's more like an air pump in an UGF to push the CO2 to the bottom of the tank and out the spray bar along the substrate.

My only concern with the idea is the forcing of the bubbles down the tubing. For your size tank there would (I imagine) be a good bit of backpressure, not to mention the gas will attempt to go back up the tubing. I would use very small diameter tubing for the downpipes to keep the velocity of water/gas as high as possible so you won't get huge bubbles forming in the tubing that might disrupt flow. The other part to that concern is what happens when the CO2 gets to the spray bar. I have an inkling that you will get 1 or 2 streams of bubbles along the spray bar instead of an even dispersion across the whole bar.

After my short time with CO2 injection I feel the best way to get good saturation is to have injection into a powerhead at/near substrate level. This gives you a fine mist that will get dispersed around the tank and slowly float upwards all the while dissolving in the water. The only problem, as you mentioned, is to limit turbulence on the plants surrounding the PH. I have a large terra cotta pot in my 20 gallon that effectively disrupts the flow of the PH, as well has having the PH set on its lowest setting. This results in an almost imperceptible current at substrate level. MUCH less than when I had the PH near the surface shooting downwards, and I get better saturation since the bubbles now have to travel a foot upwards instead of a couple of inches. If you have a piece of drift wood, other ornament, or stiff stem plant such as anubias, you can fire directly into this, and it should have a similar effect.

After trying a TON of variations on a lot of different methods, I've always come back to the simplest tends to be the best, that is force the highest contact time by injecting at substrate level, and letting the slow ascent of the microbubbles do the work for you. This also results in the least amount of "stuff" (piping, "reactors", etc) being needed in the tank. For larger tanks like yours this probably isn't much of a concern, but for those of us with small tanks (mine's a 20gallon high), I need to limit the mechanical clutter as much as possible, otherwise the fish would have no where to swim!

Let us know how it goes if you decide on your method because it is unique!

justin