CO2 Tube Diffuser (New Design?) - The Planted Tank Forum
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post #1 of 44 (permalink) Old 07-11-2018, 10:31 PM Thread Starter
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CO2 Tube Diffuser (New Design?)

Following the recent ‘re-discovery’ that diffused CO2 bubbles might benefit plants more than using a reactor (thanks to @Xiaozhuang pointing us to the T Barr study), I decided to try it. It does seem that I can drive CO2 higher (.4 increase in the Ph drop, Kh ~1dKH, pH7.2 drop to 5.4) without affecting the fish. I’m currently awaiting any change in plant performance, but have noticed a drop-off in GSA activity, probably indicative of increased plant performance. However, the purpose of this post is to share a new (to me, anyway) way to diffuse CO2.

Essentially, this is a design for laying tubing on your substrate that acts as a very long CO2 diffuser. I found that creating needle-sized holes in the urethane CO2 tubing I use allows tremendous design flexibility, while delivering minute, ceramic diffuser-sized bubbles throughout the entire tank, from the bottom of the tank. Placing the tubing under the plants allows the bubbles to get hung up in the plants. Very few make it to the surface so, absorption can occur as the bubbles stick to the leaves, which is considered ideal …and there is no swirling haze of bubbles, such as I used to get with an in-line atomizer, to affect the pristine clarity of the water.

My initial design (pictured) which covered about half the tank floor, under the plants, has been replaced with a single line that traverses the back of the tank. I have about 12” of diffusing activity on each end of the three-foot tubing (where the bulk of my stems plants are), with a non-diffuser section in the middle. The pinholes are spread along these two 12” sections at each end and there are about 3-6 holes in any given inch of these tubing sections.

The holes can be bunched in small sections of the tube for different effects and, being a tube, you can serpentine it anywhere along your floor. An additional benefit seems to be that water can not enter these pinholes when the CO2 is off. This means that check valves may not be necessary or, at least, no more worry about their failure.

To make the minute holes, I use pliers to push a small needle through the sides of the tubing. I use urethane tubing (Clippard .250” OD) and I think CO2-type tubing is necessary given the much greater wall thickness of this type of tubing. Thinner tubing, such as silicone tubing, would likely allow much larger bubbles through the holes.

You will need the pressure from a pressurized system to push the CO2 through these holes. The pressure needed is a function of the number of holes and the bubble size. If pressure is too high, the bubbles are large enough to immediately rise to the surface where they do not get absorbed well. For example; right now I have a three-foot length of tubing laid along the back of the tank substrate. Many holes are in the first foot and the last foot (nothing in the center). Given the number of holes I have, I am sustaining about 35 ppm of CO2 with 15 psi in a 29-gal tank.

To plug the end of the tube, I use a plug for drip irrigation (Rainbird – 30 of them for $7 on Amazon), but you might be able to melt the tube end closed. I also use drip irrigation parts for the various “T”, right-angle and other connectors, as well as the long black tube that runs along the inside corner of the tank top to the substrate where it connects to the main urethane tubing (pictured). The CO2 and drip irrigation tubing comes coiled. To straighten it out, I straightened a wire hanger, inserted it into the tubing and placed it in an oven for 10 minutes at 150F.

The process I use to optimize the bubble size and CO2 ppm is this:

I start with the tubing configuration mentioned above (your design may be different based upon plant layout, tank size, etc.) and about 20-25 psi. I lay this in the front of the tank to observe the bubbles. Usually, it starts by having large bubbles that immediately rise to the surface and are wasted. However, it can take a few hours for the bubble sizing to settle in, so wait at least three hours to see if any changes are needed. The bubbles, ultimately, should be so small that they rise very slowly and are difficult to see from several feet away, much like a ceramic diffuser would create. If you still have large bubbles after three hours, put more holes in the tube. Repeat this process until you have no large bubbles for a day. Then place the tubing where you want it. Now, you can adjust the pressure as you need to reach your CO2 ppm target.
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Last edited by Deanna; 01-19-2019 at 01:09 AM. Reason: Update
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post #2 of 44 (permalink) Old 07-11-2018, 11:51 PM
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pictured?

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post #3 of 44 (permalink) Old 07-12-2018, 12:01 AM Thread Starter
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Delete - not relevant to topice?

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post #4 of 44 (permalink) Old 07-12-2018, 12:02 AM
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There is a distinct lack of picture haha

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post #5 of 44 (permalink) Old 07-12-2018, 12:09 AM Thread Starter
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Delete - not relevant to topic

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post #6 of 44 (permalink) Old 07-12-2018, 01:03 AM
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I don't see a pic or even a broken link or anything. Just looks like a normal post. If you hadn't said "pictured" I wouldn't have had a clue. Weird...

Sounds like an interesting idea though. I was recently thinking about DIYing a PVC return that sits along the substrate. Maybe I'll combine the two and add some tubing just below the holes in the PVC..

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post #7 of 44 (permalink) Old 07-12-2018, 02:03 AM Thread Starter
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post #8 of 44 (permalink) Old 07-13-2018, 04:40 AM
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No pic, and Im not seeing a link or bbcode in the quote.

As for the idea it sounds interesting (too bad we cant see it!) You can also cram a piece of regular cotton ball in the end of the line to make fine bubbles, or a bamboo chopstick


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post #9 of 44 (permalink) Old 07-14-2018, 01:59 AM Thread Starter
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Quote:
Originally Posted by burr740 View Post
No pic, and Im not seeing a link or bbcode in the quote.

As for the idea it sounds interesting (too bad we cant see it!) You can also cram a piece of regular cotton ball in the end of the line to make fine bubbles, or a bamboo chopstick
Can't figure it out: I can see the picture in the post, but no one else can. It's via a BB code. Can't even post the url as a link. No response from tech support. I'm wondering if they are having site problems. Here is the BB code ...if it's any help:
https://www.plantedtank.net/forums/p...ctureid=107527
Can also send you a picture.

Unlike an in-line atomizer (creates hazy tank), ceramic diffuser (single-point heavy stream of minute bubbles) or a cotton ball, this provides the opportunity to have streams of CO2 (ceramic diffuser-sized bubbles) come up from the substrate level anywhere in your tank at points of your choosing (mine are coming up through the interior of the stem plants). So, because they can be spread out across the entire tank, the streams are very small, making them difficult to see. However, the combined effect is a lot of CO2 being put in (I'm now pushing a 2 point pH drop and fish are fine). If you like the look of bubbles coming up here and there in a heavier stream, you can group the holes anywhere along any length of tubing you want to use - great design flexibility.
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post #10 of 44 (permalink) Old 07-14-2018, 11:04 PM
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I'm basically picturing a soaker hose type concept except opposite of how it would be used in a garden.

My concern would be around clogging in the long term. If any of them stop putting out CO2, would it be very apparent? How do you clean that out when it does?
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post #11 of 44 (permalink) Old 07-15-2018, 08:28 PM
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Even clicking on your link does not show a picture for me. I like the concept a lot, especially since it eliminates a lot of the plumbing difficulties and potential hazards (e.g. leaking inline atomizer). What PSI are you running from your regulator? I'm guessing this would also be dependent upon the length of tubing and number of holes.

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post #12 of 44 (permalink) Old 07-16-2018, 01:38 AM Thread Starter
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Quote:
Originally Posted by natemcnutty View Post
I'm basically picturing a soaker hose type concept except opposite of how it would be used in a garden.

My concern would be around clogging in the long term. If any of them stop putting out CO2, would it be very apparent? How do you clean that out when it does?
Similar concept to a soaker hose, although I first visualized it when thinking about my drip irrigation system. Shouldn't be any clogging. What would clog it? There is no back-flow through the system. Any conceivable clogging would also apply to the clogging of any CO2 tubing into a diffuser or reactor, of which I have never heard about.


Quote:
Originally Posted by sdwindansea View Post
Even clicking on your link does not show a picture for me. I like the concept a lot, especially since it eliminates a lot of the plumbing difficulties and potential hazards (e.g. leaking inline atomizer). What PSI are you running from your regulator? I'm guessing this would also be dependent upon the length of tubing and number of holes.
Yeah, I can't get any response from TPT on the picture posting problem.

Current PSI is about 30, only because that's what I've been running all along. When you speak about length and number of holes, you are probably thinking about the length of the tube beginning from the first hole (my tubing, up to that point, is about 40 feet from the regulator). There will be varying levels of bubbles along the path, but my observations are that each hole is producing some amount, perhaps a little more near the end.

If either of you want pictures, I can pm them to you.
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post #13 of 44 (permalink) Old 07-16-2018, 02:32 PM
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Deanna could you send me a picture.
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post #14 of 44 (permalink) Old 07-16-2018, 10:53 PM Thread Starter
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Deanna could you send me a picture.
Sent. Let us know if the link is view-able.
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post #15 of 44 (permalink) Old 07-17-2018, 12:30 AM
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Deanna the link did not work.
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