DIY CO2 System - How to do it - The Planted Tank Forum
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post #1 of 33 (permalink) Old 06-01-2012, 09:53 PM Thread Starter
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DIY CO2 System - How to do it

This is the 19,999th thread on this subject! But, maybe it will help someone. And, maybe I will get a Pulitzer Prize!

I'm making a two bottle, 2 liter bottles, DIY CO2 system, with a powerhead (internal filter) as the diffuser. Right now I am still waiting for the check valves I ordered on Ebay - 20 days since I paid for them, but that's another story.

I am using two club soda bottles that sat in our pantry for about 2 years, long enough to be pretty sure my wife won't miss them. And, for a bubble counter/yeast filter I'm using a 500 ml bottle that had sugar free, zero calorie lemonade in it.

The club soda bottles get a 3/16" hole in the cap, drilled from the inside out to try to avoid tearing the seal inside the cap.

A short piece of air tubing, cut at an angle goes in the hole. I poked the sharp end in the hole from the inside of the cap, then used a pair of needle nose pliers to pull the tube into place.




The second bottle was done the same way. Notice that I drilled the holes off center, since there is always a little raised spot on the center which can make the drilling harder to do.

My bubble counter was made the same way, except with two tubes in the cap, one long for the CO2 to enter, under the water in the bottle, and one very short, to let the "filtered" CO2 out, heading for the diffuser in the tank. I picked the lemonade bottle by searching the grocery story for bottles with larger than usual caps, to allow more room for the two tubes.

I have a tee fitting, from the LFS, in the inlet tube, so I can hook up two bottles of yeast/water/sugar. There will be a check valve at the outlet from each bottle, so I can disconnect a bottle for replenishing the mixture without losing much CO2 or introducing much air in doing so.

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post #2 of 33 (permalink) Old 06-01-2012, 10:25 PM Thread Starter
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The CO2 diffuser will be an internal filter, a Cascade 300, that I have had for a few years.


It has two filter chambers separated by dividers with small slits for water passages.


The CO2 will bubble through a check valve in the lowest chamber, through tiny slits, which will reduce the bubble sizes through another chamber and through more slits, to the powerhead rotor, which I modified per a Tom Barr method.

I used nail clippers go split each paddle into two thinner paddles, then slightly bent them to misalign them. This makes the rotor act similar to a needlewheel rotor, further chopping the bubbles into very tiny ones, without much affecting the flow rate.

Since this will be vertical in the tank, the CO2 will all float up, with none of it escaping the rotor. With the check valve inside the filter chamber, there should be no water migrating back down to the bubble counter, a usual problem with CO2 systems.

This is for a 65 gallon tank, not an easy one to get a good CO2 level in with DIY, so I want a good diffusing method, even at the cost of having CO2 mist in the water. I'm doing this because I use low light, about 30 micromols of PAR, and my plants grow too slowly, and not reliably enough to suit me, but I like the absence of algae problems too much to increase the lighting. This should give me enough CO2 to improve the plant growth even though it isn't at all likely to come close to 30 ppm.

Now if I can just get the check valves.

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post #3 of 33 (permalink) Old 06-01-2012, 10:53 PM
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Awesome write up Hoppy! I might have to pull out my old penguin 550 powerhead and try that " half ass needle wheel" trick! Really neat and creative stuff.

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post #4 of 33 (permalink) Old 06-02-2012, 12:32 AM Thread Starter
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Awesome write up Hoppy! I might have to pull out my old penguin 550 powerhead and try that " half ass needle wheel" trick! Really neat and creative stuff.
I don't get credit for this - Plantbrain originated this modification and tested it out. I'm just finally finding a use for it.

My check valves finally showed up today.

One check valve, allowing flow out of the bottle, for each bottle


One check valve in the internal filter, allowing flow into the powerhead portion.

I bought 4 of them, so I'm using the fourth one as a connector for the tube from the bubble counter to the tube into the diffuser (internal filter). Hopefully, I will get this set-up in the tank this evening. Timely, because I just planted some more stem plant cuttings.

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post #5 of 33 (permalink) Old 06-02-2012, 02:00 AM Thread Starter
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It is installed now! Unfortunately, I didn't have as much sugar as I thought, so I ended up with 2/3 sugar 1/3 Karo syrup. My proportions are 1 1/2 cup sugar/syrup, 1/2 tsp bread machine yeast, 1/2 tsp baking soda, in 2 liters of water, roughly - up to the end of the cylindrical part of the bottle and a half inch higher. I soaked the yeast in slightly warmed water, then poured it into the water/sugar/baking soda mix, and topped off the water.




The diffuser is low, at the back of the tank, with the water flow aimed to graze the back of the tank, so it doesn't blow down the stem plants. No CO2 bubbles yet, of course. That will take a few hours to stabilize, and a few more hours to remove the air in the system.

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post #6 of 33 (permalink) Old 06-02-2012, 04:09 AM
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I have never seen this before (I don't know a thing about Co2) but your step-by-step pics and descriptions are fantastic - I have confidence that even I could do this now!
Thanks Hoppy!

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post #7 of 33 (permalink) Old 06-02-2012, 04:27 PM
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Nice setup, Hoppy! I like how you used black tubing rather than the clear. Is it much more expensive? I've never seen it in our LFS.

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post #8 of 33 (permalink) Old 06-02-2012, 04:46 PM
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Nice write up, Hoppy. Thanks.

Thinking about it now--for those of us with an ol' HOB sitting in the cabinet--I wonder if using a small HOB filter, just for CO2, would be useful (as opposed to the simple tubing and chopstick I'm currently using for my DIY CO2). Do you think the gas exchange as the water flowed from the filter and back into the tank would nullify some of the CO2 that was initially injected into the HOB? (EDIT: this was a sudden thought and I haven't searched on it.)

I tried placing the CO2 'diffuser' near the intake of my Fluval 206 but the filter housing collected the CO2 until it piled up and dumped large amounts into the tank every few minutes. Any fish in its path was noticeably put off by this! So...

Sewingalot - I've seen black tubing at my local Pet* stores. It's priced about the same.

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post #9 of 33 (permalink) Old 06-02-2012, 06:04 PM Thread Starter
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Nice setup, Hoppy! I like how you used black tubing rather than the clear. Is it much more expensive? I've never seen it in our LFS.
Oh Gee! I don't have my acceptance speech written yet

I got the tubing from a LFS near me, and it was available in 10 foot lengths, where the clear wasn't. Then I decided I liked the black color better too. It was $3 for 10 feet.

DIY CO2 is almost always on the low end of being enough to do much good, so I think it is worth the effort to find a way to make the diffusing process as efficient as you can. A HOB filter is likely to outgas a significant amount of the CO2 before it can be used by the plants, so I wouldn't try that. There used to be a very tiny cheap internal filter, the Elite by Hagen, sold only at Petco, that worked well as a diffuser, and was a very popular diffuser for a few years after a writeup on it in APC. I still have one of those also, but I wanted more water circulation in my tank so I decided to use the larger Cascade one I also had. Another efficient diffuser is the traditional external 2" PVC pipe method, but that requires a water pump or canister filter, and I'm not using that on this tank.

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post #10 of 33 (permalink) Old 06-02-2012, 06:24 PM Thread Starter
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16 hours later, and the bubble counter shows 1 bubble per second. The diffuser chirps loudly with each bubble going through, and that happens 2 times per second, so the idea of running the CO2 through the slitted filter chambers is chopping the bubbles into half size bubbles. All is working fine, but, as usual this is a somewhat noisy diffusing method.

The lights just came on. You can't see the bubbles! If you look very carefully you can see the haze of microscopic bubbles leaving the little internal filter in bursts. But, it takes a really good eye to spot the bubbles in the water - they really are microscopic. No champaign look at all. Now, this is true CO2 mist.

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post #11 of 33 (permalink) Old 06-02-2012, 09:13 PM
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I'm not sure if you've got the room or not but if you can fit an air stone in the filter, it will make a big difference in noise.
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post #12 of 33 (permalink) Old 06-02-2012, 09:51 PM Thread Starter
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An air stone was my first choice, but I found I don't have one. And, I wanted the check valve there to hide it. If my wife gets too upset about the constant chirping I will try the airstone. I could probably put it downstream of the check valve right where it is. Unfortunately they tend to disintegrate with CO2 going through them, in my experience. Maybe a really good quality one might last a long time.

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post #13 of 33 (permalink) Old 06-02-2012, 10:56 PM
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Stick the end of a bamboo chopstick in it in place of air stone
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post #14 of 33 (permalink) Old 06-02-2012, 11:19 PM Thread Starter
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Stick the end of a bamboo chopstick in it in place of air stone
How long do those last before plugging up or disintegrating? I have some bamboo chopsticks, so the cost is about right.

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post #15 of 33 (permalink) Old 06-04-2012, 12:11 AM Thread Starter
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I found these, http://www.wayfair.com/Hagen-Elite-M...4-HGE1777.html at an LFS near me and bought a 3 pack of them, and installed one on the end of the check valve shown below


Now it makes a lot less noise, just an occasional slight click as a bigger bubble goes through, and the mist in the water is still very good.

After about 24 hours I can see an effect of the CO2. I have a little clump of Rotala cuttings that has just stayed alive, no growth for 2 months now. It is now green, with about 3/4 inch of new growth with bigger leaves. I expected this, having seen the effect on my last tank. I can't see any change in the other plants yet.

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