# An incredibly simple CO2 reactor



## ed seeley (Dec 1, 2006)

I've decided to set this up as a separate thread, rather than adding it to the DIY reactor sticky as this design is way more basic IMO than the ones posted there.

My idea started when i got my JBL Easy 2 CO2 kit just before christmas.
I set up the kit as instructed with the JBL Vario diffuser in the tank. The bubbles shrank as they climbed round the diffuser but lots of the gas collected in the cap at the top. This then belched out irregularly once the amount built up. As far as I am concerned this was a complete waste so I tried to improve diffusion.

First I directed the filter output directly at the diffuser. No reall difference so next I connected the nipple on the cap to a piece of airline and connected the other end the the outlet of the filter. I did this by making a hole in a piece of filter tubing and pushing the airline, cut at a sharp angle, into the hole. This then connected onto the bend of the filter output.


















At first i set this with the airline angled cut facing towards the flow so that water was forced up the airline into the diffuser. This definitely had an effect on diffusion, but gas still collected at the top so i turned the airline around and it now functioned as a venturi, sucking water and any gas up the airline and out into the filter output. This meant little bubbles came jetting out of the outlet every so often as the CO2 built up at the top of the diffuser.

However this was still wasting a fair bit of the gas, IMO, so i had to think of another idea.

I have, quiet conveniently, a now unused gravel cleaner and a spare top for it (after i broke the last gravel cleaner!). These fit together and i have used them in the past to treat rainwater by syphoning water through it and putting carbon and floss inside among other things. This would make the perfect simple CO2 reactor, with Bioballs to break up the water flow and an airline connector to connect the CO2 pipe to.









To inject the CO2, I would put an airline connector into the tubing upstream of the reactor and the CO2 would enter here, be mixed into the flow of water like a venturi, then swirl around the bioballs in the reactor and mix with the tank water. It also has the advantage of only cutting a hole into a piece of tubing that can always be chucked if it didn't work!









To prevent leaks I siliconed all the pieces together. This meant carefully cleaning everything with meths,








then applying silicone, putting everything together and leaving to dry.









Once all the bits dried, I connected the tubing up to my external filter outlet pipe. I zip-tied it to the stand to keep the unit upright, but did this while the unit was empty and the reactor stayed full of air! I turned it upside down to remove all the air then connected it back up. After checking for leaks (none yet!) I turned on the CO2.









So far it's been running since boxing day (4 days) and i seem to have 100% diffusion with excellent pearling on the plant leaves. A small amount of gas builds up at the top during the day, but the CO2 is switched off about an hour before the 55W light goes out and by then all the excess gas has dissolved. I'm very happy so far. The only problem is the silicone hasn't stuck to the tubing, but there are no leaks at that point. I might try PVC pipe glue, or put a larger ring of silicone all around the tubing so it can't come off.


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## John N. (Dec 11, 2005)

Ed, great little writeup, and story of trial and error to go with it. The place where your reactor is different from the others out there is the CO2 input side is embedded directly into the tubing line, rather than attached to the reactor itself. Are you concerned that the flexibility of the tubing, and any movement will cause leaks around the silicone (or other future glue) and the CO2 input barb? 

Basically, wouldn't it just be a simple procedure to attached the CO2 input barb directly in the reactor part which will ensure a better adhesion of the barb to the plastic?

-John N.


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## ed seeley (Dec 1, 2006)

Thanks very much John.



> Basically, wouldn't it just be a simple procedure to attached the CO2 input barb directly in the reactor part which will ensure a better adhesion of the barb to the plastic?


In a word, yes! But the thing is that to start with i didn't want to put holes in anything that i only had 1 or 2 of in case it didn't work! If i had to throw away with a hole in it, I thought that if it was a bit of tubing, fair enough!

I also quite like the way the CO2 injected into the water flow is working at the moment. The gas is dissolving completely and i only get a few very, very tiny bubbles coming out in the outlet flow. If i injected CO2 straight into the reactor, with the lower velocity of the water in there, i would have to add it to the base of the reactor and if I did that I thought i would be best breaking up the CO2 into smaller bubbles using a simple airstone type diffuser of some sort.

I have seen a very nice piece of equipment in another thread http://www.aquaticplantcentral.com/forumapc/do-it-yourself/34940-how-to-inject-co2-into-rena.html#post260194 and this would solve the problem of leaking, but keep the CO2 going in at the same point. I'm going to see if I can get something similar over here!

Hope that shows why I've gone with this choice! Of course after a few more weeks I might realise what a huge mistake this is, but I don't think so....


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## banderbe (Nov 17, 2005)

The gas accumulating in the top of a reactor is not a sign that the reactor isn't efficiently dissolving CO2.

Most seem to believe that the gas that builds up in the top of a reactor is gas other than CO2.

CO2 dissolves readily into water fairly rapidly with ease. Even if the bubble at the top of a reactor were CO2 it would still dissolve into the water since the water surface is at the bubble's bottom.

For anyone interested I'm using a Red Sea 500 and getting outstanding results.


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## ed seeley (Dec 1, 2006)

The gas that's accumulating at the top of my reactor is just because of the shape of the end caps that i have used. They are conical and as the water/CO2 mix rushes in and hits the bioballs some of the CO2 collects there. As the water rushes past, some of the gas gets sucked in, tumbled and mixed around and dissolves. Really 'accumulate' is the wrong word, it's just gathering there temporarily!


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## ed seeley (Dec 1, 2006)

I wonder if anyone can help.
My CO2 Reactor has been running for a little while now and is doing a great job. The drop checker is showing CO2 ppm of 30 when it is on and the plants are pearling nicely!

I have fitted a glass bubble counter so I can more accurately monitor and adjust the bubble rate, but this is not proving too successful. The pressure in the tubing is fluctutating with the filter output (obviously something to do with the impellor in the filter) and this is causing the CO2 bubbles to come out in fits and starts. This makes adjusting the bubble rate tricky at best.

Also when the solenoid turns the CO2 off, water is being pushed down the CO2 tubing. I have a JBL non-return valve just ahead of the regulator so the water can't get that far, but it does go into the bubble counter and I have to reset the amount of water in there when the CO2 goes back on in the morning!

Why is this happening? Is this normal and is it just because of the pressure from the filter outlet and because the reactor is below tank level? Is it because I have a fairly long length of CO2 tubing (It is the black JBL tubing supplied with the Easy 2 kit)? Or is there a CO2 leak somewhere (all the fittings seem very secure)?

Can anyone help? I'm assuming the best way to solve it would be to add another check valve after the bubble counter so that the water cannot flow back in? Will this work?


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## DougC (Aug 4, 2006)

I've done a similar reactor (old gravel vac and bioballs on the outflow of an external filter) I added some heavy stuff in the bottom of it too so it wasn't so buoyant. I'm using diy CO2 presently but the principle is the same. I reckon that much of the gas accumulating in the reactor will be the likes of methane or nitrogen produced in the external filter. I built in a bleed tube to let this stuff out periodically.

My guess about the suck back of water when you shut off is that as the residual CO2 in the pipes get dissolved the water follows it back up the tube.


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## gibmaker (Jan 3, 2007)

ed seeley said:


> I've decided to set this up as a separate thread, rather than adding it to the DIY reactor sticky as this design is way more basic IMO than the ones posted there.
> 
> My idea started when i got my JBL Easy 2 CO2 kit just before christmas.
> I set up the kit as instructed with the JBL Vario diffuser in the tank. The bubbles shrank as they climbed round the diffuser but lots of the gas collected in the cap at the top. This then belched out irregularly once the amount built up. As far as I am concerned this was a complete waste so I tried to improve diffusion.
> ...


excelent idea, and great job. You can also do the exact same thing you are doing with a power head if you do not have a external filter (and I dont and I truley regret iit in my 125 gal discus tank) just attach the power head to the top of the gravel cleaning tube and put a filter in the bottom of the gravel tube and run co2 directly into the tube the power head churns the co2 around and the filter in the bottom stops bubbles from escaping. I currently do this on my 125 with diy co2 , and everything looks beautifull, again good job very creative. Its always awesome to see your own creation working and doing exactly what you wanted it to!!!!!!


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## ed seeley (Dec 1, 2006)

Thanks for your comments guys.



> Its always awesome to see your own creation working and doing exactly what you wanted it to!!!!!!


Couldn't agree more! Thanks.



> My guess about the suck back of water when you shut off is that as the residual CO2 in the pipes get dissolved the water follows it back up the tube.


I thought this, but the water goes down the tubing so quickly I don't think this can explain it all. Of course I might be wrong. Do other people who use external reactors, especially those sited under the tank, find this happening when the CO2 goes off?


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## tutquarium (May 27, 2005)

Hi, Ed,

I am using a JBL CO2 set vario 500 (a previous model). When I first set up the device and saw the accumulating gas under the cap, I had really been upset, but after re-reading the user manual i recognised it was written that it was by-product of CO2 which is not CO2 itself in fact. So I did not bother too much and I have been still achieving the required CO2 levels in the tank. I am actually not so sure whether such work is needed or not. Of course, I don't want to say that what you do has no point. Moreover, if what you did is something that must be done, then I can achieve the same levels by decreasing the bubbles/second rate and provide the pressurised bottle last longer. But how can we make sure that the gas under the cap is really undissolved CO2 (or an amount of CO2 which is worth to force it to be dissolved)?

On the other hand, I have been having the same back-suction problem especially when the pressure in the bottle dropped. I will be waiting for the other aquarists' comments


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## ed seeley (Dec 1, 2006)

Anubias said:


> I am using a JBL CO2 set vario 500 (a previous model). When I first set up the device and saw the accumulating gas under the cap, I had really been upset, but after re-reading the user manual i recognised it was written that it was by-product of CO2 which is not CO2 itself in fact. So I did not bother too much and I have been still achieving the required CO2 levels in the tank. I am actually not so sure whether such work is needed or not. Of course, I don't want to say that what you do has no point. Moreover, if what you did is something that must be done, then I can achieve the same levels by decreasing the bubbles/second rate and provide the pressurised bottle last longer. But how can we make sure that the gas under the cap is really undissolved CO2 (or an amount of CO2 which is worth to force it to be dissolved)?


I read that and to be honest was unconvinced by the explanation they gave!
If there is other gas in the cylinder (apart from tiny amounts of trace gases that would be so little you wouldn't see it) then the quality control of the company producing the cylinder is, IMO, not good enough. Producing pure CO2 is not that hard for chemical companies. There shouldn't any "by-product" from what I understand.
The other explanation, and the one that I'm pretty sure is correct, is that a lot of the gas that accumulates at the top of the JBL unit is gas that has come out of solution in the tank water into the bubble as it travels up the ladder and into the large bubble at the top of the unit. The thing is I have a Nutrafin ladder with a Yeast CO2 unit in another tank and the bubbles that produces shrink to a much smaller size by the time they get to the top of the ladder.
I was getting OK CO2 levels with the vario, but not the 30ppm I was aiming for without turing the bubble rate way up and losing lots of gas. I now have just under 2bps feeding into the reactor and that's only for about 8 hours a day as i turn it off an hour before the main lights go off so hopefully I'm now more economical on the CO2 than with the diffuser and getting better CO2 levels - exactly what I was hoping!
I've also got the pretty huge diffuser out of the aquarium!

Still wondering what's going on with the water back-flowing when i turn the CO2 off! Help! Anyone! Do other CO2 diffusers have this issue?


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## adamt (Oct 21, 2006)

Did you install a check valve on the co2 line? If water is flowing into the co2 line at the place where the tube goes into the reactor, it would probably help if you installed a check valve right there so nothing can back flow.

Not to insult your intelligence, but a check valve is simply a valve that only allows a substance to flow through it in one direction.


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## ed seeley (Dec 1, 2006)

Adamt you certainly didn't insult my intelligence! I'm sure we all know it's all too easy to miss something very simple and not be able to see it ourselves!

I have got a check valve. I've installed it just after the solenoid valve.

My set up is as follows;
500gram CO2 cylinder > JBL Easy regulator > JBL Solenoid > Short (3"/7cm) length of JBL, black, CO2 proof tubing > JBL Check Valve > Long (about 1.6m) length of the same tubing > Boyu glass bubble counter > Short (5"/12cm) length of tubing airline connector into filter tubing above CO2 reactor.

Can I add another check valve between the CO2 reactor and the bubble counter without compromising the flow of CO2? Obviously every check valve added works by creating back pressure that the CO2 has to push against, but, as the CO2 is pressurised will an increase in the back pressure make any difference?


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## adamt (Oct 21, 2006)

If I were you I would put a check valve right at the end of your co2 tubing where the line connects to the filter line.

Did you ever find one of those reducing "T" hose barbs?


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## ed seeley (Dec 1, 2006)

No I didn't, but thanks for asking. It seems no one sells them over here and thought it was a bit excessive to ship it all the way from the states!

At the moment the airline connector is fine just in the tubing and not leaking, but I'm going to make my own version by buying a normal 12mm connector, drilling a hole in it and using PVC pipe glue to glue an airline connector in! I think when I do i'll also add a valve to bleed off excess air from the reactor after water changes and filter cleanings as that would be very convenient.


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