Pressurized CO2 diffusion? - The Planted Tank Forum
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post #1 of 6 (permalink) Old 02-27-2011, 06:23 AM Thread Starter
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Pressurized CO2 diffusion?

Being an Evil Mad Scientist in training, I always closely monitor the activities of the folks over at When I saw this article about carbonating small fruit recently it got me thinking:

The "standard" way of diffusing CO2 into liquid (for soda, etc.) is high pressure & low temperature. The low temp isn't really doable with an aquarium, but the CO2 is already at 900 psi or so. The trick would be getting the water to that pressure and then back to atmospheric.

Now, I know this is over the top complicated and current diffusers and reactors are probably plenty efficient, but I subscribe to the theory that anything that is worth doing is worth over-doing, so on with the gendankenexperiment.

I am envisioning a pressure vessel with a water input valve, CO2 input valve and two water output valves, one restricted and one unrestricted. A controller opens the unrestricted water in and out valves to flush CO2 depleted water into the chamber. After a suitable flush period, all water valves are closed and the CO2 valve is opened, bringing the pressure in the chamber up to the full pressure of the CO2 canister. Again a suitable time is allowed to pass while the CO2 diffuses into the water. Then the CO2 valve is closed and the restricted water outlet valve is opened, allowing the chamber to return to low pressure without a fish-killing water-hammer shock. Then cycle begins again and the CO2 enhanced water is flushed into the tank.

Complicated? Yep
Dangerous? Of course! (Don't try this at home kids!)
Will I build one? Probably not.

But hey, sharing crazy ideas is fun. And you never know, maybe someone will read this and it will spark an idea that is actually workable.

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post #2 of 6 (permalink) Old 03-01-2011, 04:46 AM
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Meh doesn't sound that dangerous, I wonder though if you'd need some kind of agitation inside the cannister itself to ensure full diffusion of the gas, otherwise I could see some stratification occurring.
It is a good idea though, the release of the enriched water would have to be fairly gradual or a excess of co2 in the tank could occur fairly quickly I would think
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post #3 of 6 (permalink) Old 03-01-2011, 05:33 AM
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I was just thinking about this earlier today when drinking a can of root beer. I'm not sure how well this would work in small scale, but for those who run large scale planted tank operations, perhaps in a fish store, they could probably apply this method to their sump system with zero Co2 waste
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post #4 of 6 (permalink) Old 04-08-2011, 05:27 PM
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Newb here!

I've got a better idea for you:
Keep the pressure vessel under C02 pressure all the time.
Use a high pressure water pump to pump the water into the pressure vessel.
Slowly trickle the C02 rich pressurized water into your tank allowing it to mix with the rest of the tank water.
Add a float switch to the inside of the vessel to automatically pump more water into the vessel when it gets low.
You could probably have this setup built for you out of stainless steel for $1000 or so.

Or just go to e-bay and search for "carbonator" and pick one up for about $100 or so depending on your ebay skills.

I apologize for my smart remark but a commercial carbonator for soft drinks would be perfect for this and works exactly as I described above.

I haven't had a tank for 20+ years and now that I have a couple of small children (6 and 7) I am looking at putting one together again. After much reading and research on this board and others I think I will go the continuous water change route. I.e. a constant trickle into my yet to be tank and the overflow being continually flushed down the drain or into the garden. I am on well water and even already have a reverse osmosis system under the kitchen sink thanks to the previous owners. I am seriously thinking of buying a carbonator to carbonate the new incoming water. As a side benefit I will also be able to enjoy fresh tasty carbonated well water when ever I want (Carbonated water is my favorite drink as well as my daughters).

BTW: My name is Mike. I love to build stuff and building a fish tank almost has more appeal to me than just having one. I currently have acquired a 35 gallon hex that was represented as a 50 gallon (I should have checked before buying). Tonight I will be looking at a xtra-tall 110 gallon glass complete setup with hood and fluval 404 and stand ($250 obo). I just received my eheim 2075 yesterday. If I buy the 110 the stand will have to be replaced as my main hobby is woodworking and I also do some welding and metal fabrication. I am really crossing my fingers that the tank will be pre-drilled for bulk heads (I believe I have picked up the term "reef ready" to describe this?).

Love the site and especially the DIY forum!!!!
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post #5 of 6 (permalink) Old 04-08-2011, 09:42 PM
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Welcome Oughtsix!

I sincerely hope you post a thread with pictures if you get to building a carbonator for your Co2 injection system. I am very interested to see how this works
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post #6 of 6 (permalink) Old 04-09-2011, 06:46 AM
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Thank you for the welcome. My plan for a beautifully engineered underwater forest kind of got put on hold for quite a while tonight. I went to look at a 110 gallon xtra tall for building said forest. $250 for the 110 glass, fluval 404 canister, magnum canister, hood and stand. I couldn't pass it up. The only problem is it came with 5 beautiful Cichlids. I was thinking of trading them in for schools of tetras but we fell in love with them! So eventually I will have the beautifully planted 35 gallon hex. But it is going to take a while to learn and get aquainted with Cichlids in the 110 gal first.

I do see a continuous water change in my near future! I cringe at the thought of drilling the 110 for the overflow but don't want to rely on a siphon to keep from flooding.
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