Timed internal reactor for DIY CO2 - The Planted Tank Forum
 
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post #1 of 15 (permalink) Old 12-03-2014, 04:01 PM Thread Starter
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Timed internal reactor for DIY CO2

Hello, I'm new to the forums. Well, I just registered anyway. I'm familiar with the site, it's been a great source of ideas and information.

This has been working great so far, so I thought others might find it useful.



The problem with DIY CO2 is that you can't simply shut it off, so you have to adjust the yeast/sugar recipe and then count bubbles, which can be unpredictable. I've been experimenting with DIY internal CO2 reactors, and this is what I came up with. The idea behind this project was to make an internal reactor for DIY CO2 that can be turned on and off with a timer, and allows excess gas to escape to the surface, giving you some control over the amount of CO2 being dissolved into the water.

Unlike other similar DIY internal reactors, the powerhead can be turned off without CO2 accumulating in the impeller chamber, causing an air lock. The gas will escape out the side of the reactor instead of going up the outlet into the impeller chamber, so this one can be switched off and back on again without the need to re-prime the powerhead.

When it is turned off, it just functions as a "bell" type reactor that traps the CO2 in the bottle, with only a minimal amount of CO2 being dissolved into the water, and most of it escaping through the hole in the side and bubbling to the surface. Once it is switched on, the flow of water enables a much higher dissolving rate, and all of the CO2 coming in should get dissolved without any of it escaping to the surface. The photo shows it in action. It's hard to see the outlet hole in the side, but if you look closely you can see that the water/CO2 level stays about 1 cm above the outlet hole when it's switched on. It's kinda fun to watch it "breathe" as the level fluctuates slightly up and down (the CO2 entering and then dissolving).

This design should give you a fairly consistent amount of CO2 no matter how much gas your yeast/sugar mixture in the generator bottles is producing (if it's coming in faster than it's dissolving, the excess should just bubble out). This way, there's no risk of gassing your fish unless you're leaving the reactor on for too long. I have mine set to turn on 1 hour before lights on, and set to turn off at lights out.

another pic:
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post #2 of 15 (permalink) Old 03-31-2015, 06:13 PM Thread Starter
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Update!

Here's what I've observed after using my reactor for a few months. The photos show it being used in a 10 gallon, which has since been torn down and replaced with a 20 long. I was worried it would be insufficient for the bigger tank, but so far it has been more than sufficient.

I'm no longer concerned with getting 100% diffusion with this reactor. In fact, it's good that some co2 is escaping periodically. That just means the reactor is "running full", which tells me the generator bottles are still going strong. In other words, normally, the reactor is full of trapped CO2 while running. When it slows down, the reactor will no longer run completely full, which gives me notice that I need to change out a bottle soon. So, the reactor also functions as a gauge of co2 production.

More importantly, this reactor is self-regulating, meaning:

1) It has a consistent dissolving rate that is independent of the rate of co2 production, which really smooths out the fluctuations inherent with DIY CO2.

2) It's a fish-saver. There's no risk of gassing fish as long as it's on a properly set timer. When/if the co2 production is faster than the dissolving rate, the excess just bubbles out.

3) The trapped co2 provides a "reserve" supply for when your generator bottles start to slow down.

I'm only running two 1-liter bottles on my 20 gallon long, and the drop checker is green and never budges. It seems to always be the same color at any given time.

If I may gloat, this has proven to be a top-notch solution for DIY CO2, as long as you don't mind a bit of an eyesore in the tank (just hide it with plants!)
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post #3 of 15 (permalink) Old 03-31-2015, 07:38 PM
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How is that different than the tom Barr internal venturi reactor. I have that on a timer. No bubble lock either.
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post #4 of 15 (permalink) Old 03-31-2015, 07:53 PM Thread Starter
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Originally Posted by jrill View Post
How is that different than the tom Barr internal venturi reactor. I have that on a timer. No bubble lock either.
I'm not sure. Do you have a link or a pic? Is that one self-regulating as well?
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post #5 of 15 (permalink) Old 03-31-2015, 07:57 PM
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Here is one link. Plenty if you Google it. Not sure what you mean by self regulating.
http://www.aquaticquotient.com/forum...ad.php?t=13643
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post #6 of 15 (permalink) Old 03-31-2015, 09:04 PM Thread Starter
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Here is one link. Plenty if you Google it. Not sure what you mean by self regulating.
http://www.aquaticquotient.com/forum...ad.php?t=13643
So turning the powerhead sideways prevents it from getting air-locked? I hadn't thought of that, it makes sense. I might try that with mine if only to save some space.

I've seen similar designs, and it's quite possible I've run across Tom Barr's specific design before and just don't remember. One of the reasons I decided against a similar design is that they are "too efficient" if you follow me. It seems to me that the CO2 concentration would fluctuate up and down corresponding with the fluctuations in co2 production when using DIY. I see that his design includes a burp hole to release excess co2, but I'm guessing it can handle a fairly high bps??

By self-regulating I mean that an increase in bps will not increase co2 concentration. Since it's always running full of trapped co2, and burping regularly, the bps doesn't matter (as long as it's sufficient of course).
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post #7 of 15 (permalink) Old 03-31-2015, 09:12 PM
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Then I suppose by that definition it would be self regulating. While I have used his design in yeast diy, I currently use it on citric acid/baking soda diy co2 which is regulated by design. But on your system how much co2 are you putting in your tank. Drop checkers are very poor at telling us that. Do you know what your daily pH drop is. By knowing that you will have a better idea of how effective your diffuser is.
I hope I don't come off as a jerk here. I too am always looking for better ways to do things.
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post #8 of 15 (permalink) Old 03-31-2015, 09:39 PM Thread Starter
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Then I suppose by that definition it would be self regulating. While I have used his design in yeast diy, I currently use it on citric acid/baking soda diy co2 which is regulated by design. But on your system how much co2 are you putting in your tank. Drop checkers are very poor at telling us that. Do you know what your daily pH drop is. By knowing that you will have a better idea of how effective your diffuser is.
I hope I don't come off as a jerk here. I too am always looking for better ways to do things.
The drop checker reads 6.6 with a 4dkH reference solution, so right around 30 ppm. I was under the impression that a drop checker with reference solution was more accurate than measuring daily pH drop. If that's incorrect could you please explain? Either way, the daily pH drop is negligible since the combination of co2 produced by plants at night plus the trapped bubble of co2 in the reactor seem to keep the co2 concentration close to the same as the daytime concentration when the reactor is running. Like I said, the drop checker never budges.

To give an approximation, pH of aged tap water is 7.8, and tank pH looks to be about 6.9.
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post #9 of 15 (permalink) Old 03-31-2015, 09:45 PM
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Checkers are not very accurate. Ever notice how many post with problems directly related to co2 levels and the op says the drop checker looks right. Have some fun and read some of the later stuff tom Barr says about them. I threw mine away years ago.
De gas your a tank water sample for 24hrs. Drop 1 degree from there as a starting point.
But, others will disagree.
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post #10 of 15 (permalink) Old 03-31-2015, 09:59 PM Thread Starter
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Originally Posted by jrill View Post
Checkers are not very accurate. Ever notice how many post with problems directly related to co2 levels and the op says the drop checker looks right. Have some fun and read some of the later stuff tom Barr says about them. I threw mine away years ago.
De gas your a tank water sample for 24hrs. Drop 1 degree from there as a starting point.
It would seem to me that if drop checker looks right, but there are CO2 issues, it is most likely a lack of proper circulation. I do understand that drop checkers will take some time to respond to changes. I'll search around and see what info I can find, thanks.

I was actually considering taking my drop checker out just because this reactor seems to be so predictable. So far there's not a hint of algae to be seen (except on the rocks )

Yeah, by aged I meant de-gassed for 24 hours, so a 0.9 drop should be good right?
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post #11 of 15 (permalink) Old 03-31-2015, 10:19 PM
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Correct on aged but test your tank water not the tap.
More important or at least equally important is the amount of light. Are you running high, med or low.
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post #12 of 15 (permalink) Old 03-31-2015, 11:27 PM Thread Starter
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Ok gotcha, that makes sense, but I'm betting de-gassed tank water will still be 7.8. I've been changing 50% weekly. It shouldn't be far off if not exactly the same.

Medium light. I'm not exactly sure of PAR. Fixture is 30" BeamsWork LED, 57 X 0.5W 6500K on a 20 long (12" deep, light not suspended, legs are on the rim)

Here's a pic:
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post #13 of 15 (permalink) Old 04-01-2015, 01:33 AM
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Your tank looks very nice. The medium low light would explain little or no algae along with the co2. Nice. With less than high light, assuming that's what you have you can get away with less co2.
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post #14 of 15 (permalink) Old 04-01-2015, 02:11 AM Thread Starter
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Thanks! I should mention that I used exposure compensation when I took that photo, which gives the appearance of a lower light level. The tank is only 8 weeks along in the photo.
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post #15 of 15 (permalink) Old 04-01-2015, 02:50 AM Thread Starter
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I really wish I knew the PAR ratings for the BeamsWork. I'm definitely seeing pearling. Not like in a higher light situation, but a steady release of bubbles throughout, with the occasional singular steady stream.
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