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Harnessing CO2

Discussion in 'Homebrewing' started by SkeeterElvis, Mar 10, 2012.

  1. Anyone have any advice about how to harness CO2? Have my carboy next to my aquarium, and I want to get the CO2 in the tank for the plants.
  2. flagmantho

    flagmantho Poobah (1,105) Washington Feb 19, 2009 Verified

    I imagine a regular blow-off tube would do the trick, as long as your kräusen doesn't get up in there.
  3. Homebrew42

    Homebrew42 Savant (435) New York Dec 20, 2006

    Just out of curiosity are there fish in this aquarium? If so how do they like their water being saturated with CO2?
  4. kjyost

    kjyost Champion (775) Manitoba (Canada) May 4, 2008 Verified

    If you're worried about krausen, you could easily put a middle bottle with a carboy cap on it to catch the blow off, and then have the out tube go to he aquarium.

    HB42 does have a good question though.
  5. skivtjerry

    skivtjerry Advocate (595) Vermont Mar 10, 2006

    Injecting CO2 into the water will kill any fish present. The plants might not be happy with a big slug of CO2 either because the pH would drop rapidly as it dissolved. If you're determined to do this for some reason, use a carboy cap, catch some gas in a balloon and add it to the water v e r y slowly. Wait a day to see what happens and maybe try again.
  6. Yes, CO2 is toxic, but toxicity is highly unlikely if not impossible. If we somehow managed put enough of the gas in the tank that the pH dropped significantly, the solubility would also drop. Our KH/GH are high, and our pH is higher than desired anyway. Also, chances are, we wouldn't get enough CO2 from fermentation to sufficiently dose 125 gallons. Just trying to make some use out of free CO2 rather than having to buy so many cartridges.

    My biggest concern is fish tank water backing up into the carboy. Any useful suggestions?
  7. kjyost

    kjyost Champion (775) Manitoba (Canada) May 4, 2008 Verified

    Use an empty 1 gallon jug in the middle with a carboy cap. It keeps krausen out of the fish tank, and vice versa.

    Run hose from blow-off --> 1 gallon jug, also use the 2nd hole in the carboy cap and runs a hose to the aquarium.
  8. billandsuz

    billandsuz Savant (460) New York Sep 1, 2004

    i suppose a blow off hose directly into the tank is your solution.
    consider a 0.5 micron sintered stone on the end of the hose. this will create micro bubbles with more surface area. the gas should dissolve readily into the water. maybe. i can't say if anyone has done this experiment...

    an inline check valve will prevent backflow. if the temperature differential between aquarium and wort is great enough you could suck some aquarium into your beer.
    maybe this?

    wouldn't it be alot more convenient to spend a few dollars for a CO2 tank?
  9. Only use the method when fermenting oyster stouts?
  10. pweis909

    pweis909 Champion (800) Wisconsin Aug 13, 2005 Verified

    Your aquarium is in equilibrium with atmospheric CO2. It is highly unlikely that your aquarium plants are limited by CO2. Usually phosphorus is the limiting nutrient to freshwater plant growth. If you are keeping a saltwater aquarium, chances are that bubbling CO2 will drive the pH lower than marine species are accustomed. I really can't think of a good reason to do this.
  11. It's freshwater, and the caliber of planted tank desired requires CO2 injection faster than it will dissolve into the water in addition to several other variables including the nutrients you describe.

    Thanks, everyone, for your suggestions. After giving it more thought, I think it is not very useful only because it would provide CO2 in short intervals. But an interesting idea I'll have to table until I start forking out brews. As if I'd need any more motivation to do that!
  12. pweis909

    pweis909 Champion (800) Wisconsin Aug 13, 2005 Verified

    Sorry for my earlier advice; I did a little reading and see that aquarium hobbyists will optimize light and nutrient variables, in which case, dissolved CO2 would limit photosynthesis. Maybe a chemical approach , such as limestone saturated water, to maintain a lot of CO2? And of course, while watching your plants grow, you can drink beer, belch a lot, and raise the partial pressure of CO2 for good measure. (gotta stay beer focused...)
  13. Cut the top off a 2 liter soda bottle and attach it by some means under water inside the aquarium, open end down. Run the blowoff tube under the bottle so that the CO2 bubbles collect inside the bottle. The water will readily absorb CO2 from this reservoir at a slow enough rate (this eliminates the concern over intermittent bursts of CO2). Load the aquarium with plants to keep the algae at bay and you should be fine – the plants will thrive and the fish will get plenty of oxygen (everybody’s happy!). You should probably keep an eye on both the CO2 saturation and the pH.

    Regarding billandsuz’s comment on simply spending the money to buy CO2 for the aquarium – we do these things, not because they’re practical or efficient, but simply because we can. Rube Goldberg was a genius!