I've been experimenting a bit with various types of CO2 misting systems, and I want to pass on to my fellow aquarists (in my case a very loose term) what I personally feel for me is the best setup, especially for larger and longer tanks. I'll include web sites for procuring some of the materials I used, but there may well be some other firms with better prices, more favorable location, etc., but these are the locations and people I have dealt with and found to be efficient and reputable. Material substitution can probably done as well, it's the distribution of the CO2 that's important. I will add that there is quite a bit of misting that does occur with this system, but by adding or decreasing the flow of CO2 through a needle valve, the individual should be able to minimize the visual effect of the misting.
I have a 75 gallon tank, roughly 18"x18"x48". I mount a Rio 600 RVT pump, (available at http://www.marinedepot.com/md viewI...dproduct=TA3191) to the aft, lower left wall of the tank (as you view the tank from the front), so the output of the pump is as close to the substrate as possible, and pumping water along the length of the back wall. I place a short piece of Eheim tubing 12/16mm (available at Big Al's Online at http://www.bigalsonline.com/catalogu...tegory_id=2627) over the outlet of the pump. I then use a short piece of Eheim 16/22mm ( available at Big Al's Online at http://www.bigalsonline.com/catalog/...tegory_id=2627 ) to connect the pump to a 39" long, 3/8" clear PVC pipe, with approximately 15 #40 (3/32") drill bit holes drilled evenly along the length of the tube in a straight line, with the holes pointing to the front of the tank. The clear PVC pipe ( available at http://www.clearpvcpipe.com/index.as...ROD&ProdID=121 )was selected for aesthetic purposes, but CPVC pipe, 1/2", could also be used, which would be cheaper, but is off white in color, and very noticeable in my tank. 1/2" suction cups are used in 3 places to secure the pipe to the aft tank wall.
The misting has been terrific. The main advantage with this system is this- I have 15 separate dispersion points for points for the CO2, not a singular, inefficient outlet that requires a high pump output to disperse it, blowing plants all over the place. Admittedly, the pipe is there and visible, but there always seems to be some sort of compromise that needs to be made with almost any system or procedure. Outlet pressure could be increased or decreased by adding/deleting some of the holes, using a smaller/larger pump, et., that's up to the individual. I cannot say enough about this, I've tried stones, reactors, etc.,but nothing comes close to this.
I need to apologize to everyone, my computer skills are limited, or I would have included a diagram, and a direct method to access these websites. Best of luck with this, feel free to contact me if you need more help.

Walter :gw

I must be getting mentally slow, but I can't see in that description how you get the microbubbles of CO2 to be dispersed by that spray bar. Don't you need a difuser of some kind?

Im pretty sure what he's doing is feeding the CO2 line into the venturi intake on the power head. Basically the flow from the power head rips the CO2 bubbles into a mist as the enter and then the mist flows through the spray bar and disperses through the tank evenly.
Pretty good Idea, probably one of the most efficient ways of using a mist method if you dont mind the extra equiptment in the tank. Plus since the bubbles are starting at the bottom of the tank and being pushed directly into the plant groupings from underneath it seems as though it would maxmize the contact time for the bubbles to hit the leaves before they floated to the top of the tank, or dissloved into the water colum. Thanks for sharing the great Idea Walter!

~Matt

Exactly as colonel says, the pump breaks up the CO2 into a fine mist, and that is carried to 15 ejection points in the tank. The bar really is almost invisible, with the power head being far more visible than the pipe. Especially when the pipe is located behind and below the plants. I, like many others I'm sure, are disturbed by the mist that's created in the tank, but it really is impossible to stop- after all, one way or the other, if you're using the misting technique, which I believe is the most efficient method, the bubbles, or mist, have to go into the tank; even with an internal reactor, the reactor itself is more visible than this system, and by far less efficient. I have a Madagascar Lace Leaf plant in my tank, and it is saturated with bubbles on the leaf- utterly fantastic display! The pump, I might mention, is one Tom recommended some time ago, which really does the job. The only problem with just using the pump to distribute the CO2 is that the pump's output is quite strong, and blows the plants around far too much- hence the pipe with multiple outlets. I want to add that the pipe is capped on the end with a cap available from the same place as the pipe. Now, if someone can come up with a way to get the bubbles so small that they're invisible, that would be great! But, CO2 is a gas, and I don't see how that can be done. Even my reactor showed some sort of visible display of CO2 injection.
I want to add that I replaced the pump's venturi line and added a 90 degree plastic 1/8" elbow to that line, then reconnected. The original line was bent sharply, creating a situation where it could eventually shut off flow. Not likely, but possible. This elbow was obtained at Auto Zone

Walter, the friendly ole' :gw

This actually helps to distributes the mist better, since it spreads it out evenly.

I do the same thing for the sumps I use and feed the outflow from the CO2 reactors directly into the return lines.

You can use flexible clear tubing of anytype and hide it along the back wall, even bury it where appropriate and have little elbows pop up.

They also make those rotating powerhead flow divertors.
I use this with aeration for a marine tank.
Regards,
Tom Barr

This sounds like a great idea! Since I've rescaped, I can't position my powerhead (w/ quickfilter attachment) where I'd like. And even if I could, the "misting" is not as even as I'd like. There's definitely an advantage to CO2 misting, as shown by plants in certain parts of the tank, where the CO2 hits the bottom and rises up through the plants, but the opposite end, plant growth is well, meh...

What I'm looking for is a filter to serve mainly as a mechanical filter that has enough oomph to drive a 40-45" spraybar, as well as serve as a diffusor (direct CO2 injection). I'm thinking maybe a Marineland 350 cannister? I don't want to spend too much. I'd go with a powerhead, but they are bulky, and I need the mechanical filtration, as my Eheim 2028 can't keep the tank as clean as I'd like all on its own.

David, I will add something about the size powerhead you may need for that 45" spraybar- drill only about 5 or 6 #40 drill holes initially, to be sure you get the pressure correct. I have quite a few holes in mine, and thr Rio 600 RVT is fine for that purpose. Let me know if you come up with something for the canister, however.

Walter :gw

I think a RVT 600 is plenty to drive a mist bar for larger tank applications.

One idea is adding the limewood stone to the canister filter return.
Then using that for the CO2. You'd need a solenoid and a larger tubing section, say a little 1" PVC section and add the stone inside and a CO2 libne hole drilled and glued in place.

I'll think I'll make one here and show folks rather than explain it.



Regards,
Tom Barr

Any reason that mounting the powerhead on top would not work as well (aside from the look of the tank)?

Rich

"I'll think I'll make one here and show folks rather than explain it".

Hey, Tom, I think this is a pretty good idea. As an "Excel" user , the CO2 spraybar concept is hard to visualise. I'm finding the tech talk a bit difficult to follow. I'd love to see a simple diagram to see how this system works. While the Excel carbon-source method delivers, C02 injection appears to be a more cost efficient system in the long-term. But this is a bit of a guess.

Have the cost efficiency figures been calculated by anyone?

Robin