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CO2 issues? Read this

Discussion in 'CO2 Enrichment' started by Tom Barr, Sep 22, 2005.

  1. unirdna

    unirdna Junior Poster

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    Re: CO2 issues? Read this

    Tom, this is my verbatim post from another thread. It was dying, and I didn't know if you would see it, so I'll post it here as well. After re-reading my post, I realize that I may come off as a bit confrontational. Note that I always try to argue the argument, not the arguer ;).

    Thanks for your attention.

    ---------------------------------------------------------------


    Interesting experiment. I'm always in favor of challenging the dogma. But, there is a huge snag in my understanding of how this works. Specifically relating to my understanding of how CO2 dissolves in water.

    My own experiment: Aim my spray bar downward and bubble CO2 through the airline to the bottom of my aquarium 20 inches high. The bubble of CO2 dramatically reduces size and speed (rising to the top, against the current of the spraybar) in less than one second (it is eventually blown out of the current and slowly rises to the top of the tank). The diameter of the bubble seems to reduce in size from 4mm to approximately 1mm. Using the volume equation for a sphere (V = 4/3 • p • r³), one can quickly calculate that this would be a 94% reduction in volume (15/16). This doesn't even take water pressure into consideration - which, of course, would make the percentage even higher.

    If you are unable to perform this experiment, or question the conditions in which mine was performed, try this... If you are running an inline reactor, open your needle valve wide open on the CO2, allowing your reactor to fill up to 1/4 or so CO2. Then, see how fast that stuff dissolves into solution. Seconds! And what's left? A small quantity of seemingly "stubborn" CO2 bouncing around in the reactor? More likely some other gas that does not dissolve so easily. Why would 95-99% of the CO2 dissolve in seconds, and 1-5% "decide" to not dissolve?

    It is this (non-CO2 gas) that I think you are fighting so hard to disperse about your tank. - whether it be via your venturi method or the diffuser/water-movement method. In short, I would surmise that the reason you are seeing this pearling would be the result of oxygen super-satruation (as O2 is likely that "hard-to-dissolve gas that is being blown around the tank).

    Until a concise, scientific explanation can be offered as to why CO2 dissolves so rapidly, yet can remain as small undissolved bubbles for lengthy periods of time under turbulent conditions, the likely conclusion is that these bubbles of gas are not CO2.

    Ted
     
  2. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    You have the general idea.

    I'm coming up with some better devices to perform this.
    I just need to show a pic layout of how to make them etc

    The diffusers are better than the air stones IME.

    Regards,
    Tom Barr
     
  3. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Ted,

    The dissolving rate decreases as we over saturate the water with CO2.
    This is why we have gas build up in reactors (and some degassing of the O2, but disc and airstones do not have this issue!).
    The first hour, the bubbles are mostly dissolved, the last few hours, they are not.

    The change in ppm of CO2 in the water affects the CO2 solubility.
    It becomes harder and harder to add more beyond saturation.
    While I say this, I do not know "how hard" but it seems to be relevant and worth addressing.

    The other issue one of surface/volume area. The surface volume area is much greater with a smaller bubble, hence faster dissolving and thus faster response to dissolving the CO2 when dosing gas CO2.

    Once the CO2 ppm is high, say 20-30ppm, then the bubbbles will presist much longer(basically the reactor/disc etc are becoming more ineffecicent once you reach higher CO2 levels).

     
  4. jonathan11

    jonathan11 Lifetime Charter Member
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    Re: CO2 issues? Read this

    Tom, or anyone, can you mention a good diffuser disc to use, and possibly address the cleaning issues that seem to go with the discs? :gw :D :D
     
  5. stcyrwm@adelphia.net

    stcyrwm@adelphia.net Prolific Poster

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  6. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Those are junky IME.
    I prefer ADA, Azoo, and a few others that have a suction cup with it.

    Regards,
    Tom Barr
     
  7. stcyrwm@adelphia.net

    stcyrwm@adelphia.net Prolific Poster

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    Re: CO2 issues? Read this

    Couldn't find Azoo diffuser. ADA costs about $80. Is there a less expensive route or is that just the going price for the quality? Aquatieco ozone/oxygen diffuser seems like the best deal at $55.00......
     
  8. stcyrwm@adelphia.net

    stcyrwm@adelphia.net Prolific Poster

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    Re: CO2 issues? Read this

    Tom,

    Do you think this technique might open the door to help solve some of the limitations in a DIY CO2 situation? Or do you think DIY will have the same problems producing enough microbubbles as it does consistently staying over 30ppm??????
     
  9. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Well it sure helped my DIY issues using the Venturi diffuser.

    My DIY tanks did better than most CO2 gas tank folk's tanks.

    Azoo is sold by Aq eco also and a number of other MO places.

    Fairly cheap a good diffuser it seems.

    Regards,
    Tom Barr
     
  10. stcyrwm@adelphia.net

    stcyrwm@adelphia.net Prolific Poster

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    Re: CO2 issues? Read this

    I can't find an Azoo diffuser on Aqaticeco anywhere. I did search and went through a hundred items but no Azoo diffuser. I googled and I come up with zip. BTW what does MO stand for? Can anyone point me in right direction?
     
  11. matpat

    matpat Prolific Poster

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  12. stcyrwm@adelphia.net

    stcyrwm@adelphia.net Prolific Poster

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    Re: CO2 issues? Read this

    Tom,

    You're not talking about the "Azoo air curtain" diffuser are you? It's the only Azoo diffuser I can find. Doesn't look like much but I think they carry it at Aquatieco also, it's just not listed as an Azoo product on their website.

    Thanks, Bill
     
  13. stcyrwm@adelphia.net

    stcyrwm@adelphia.net Prolific Poster

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  14. reiverix

    reiverix Lifetime Members
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    Re: CO2 issues? Read this

    Well I got home from work and it was purely spur of the moment but I'm going to give this a go. I hunted out my Azoo diffuser that's been dormant for about 10 months, and gave it a bleach dip to clean it out. My old setup was an external reactor hooked up to an external filter. It works fine but I like tinkering if it's easy :) .

    Two things I quickly noticed. Firstly, I had only ever used the diffuser with DIY and was amazed at the bubble stream coming from compressed CO2. Secondly, I had to actually turn down my bubble count from around 4bps to 1.5 bps. I'm currently monitoring the fish and CO2 content. So far so good. To be honest I'm not expecting immediate miracles or anything like that, but if I get the same bang for using less CO2 I'll be a happy planter.
     
  15. Jay

    Jay Lifetime Charter Member
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    Re: CO2 issues? Read this

    I really enjoy the reading, concepts, and experimenting with things I learn on this forum, but rarely post. I had an experience yesterday that I just had to pass on.

    For the past two+ weeks I have been experimenting with the concept of micro bubble misting with CO2. I am using an old diffuser in conjunction with my venturi-modified reactor. The results have been dramatic, even the algae are negotiating unconditional surrender. The diffuser is old and frail and a new Azoo or Eheim is cheap enough I thought I would order one and make it a permanent part of my CO2 system.

    Have any of you taken this concept on the road yet? WOW!

    I ordered the diffuser from a fairly well know plant source (that will remain nameless). When the equipment did not arrive in a timely fashion, I called them to see what the problem was. I was put on the line with their CO2 “expert”. He immediately tried to sell me their super deluxe reactor. I declined and told him I already had one and wanted the diffuser. He asked why. I told him I was experimenting with micro bubble misting to improve plant growth among other things. He then proceeded to “T” off on me. The concept was the most “Stupid” thing he ever heard. What “idiot” gave me this idea? A visible bubble is a waste of CO2 no matter what size. On and on, about what a scam this was, I could not get a word in.

    I finally got to ask if he was going to send my stuff. He said NO he was out of inventory. He also said that he thought he had several hundred in house but they were all gone.

    Curious, I remarked. Just credit my account and I’ll move on. I wonder where they went?


    Jay
     
  16. matpat

    matpat Prolific Poster

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    Re: CO2 issues? Read this

    Do you have any pics of our venturi modified reactor???

    I played around with my DIY reactor by adding a Kent Turbo Venturi to the intake and it quickly dropped the pH in my 75g about 0.3 in 10-15 minutes without increaseing the bubble rate.

    The Turbo Venturi works well without a reactor also but the Quiet One pump I used is a bit too loud for my taste.
     
  17. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    I did not mention this idea to folks just sitting in my room one day "thinking", I did the method and saw the results first, then thought about it.

    Folks that try it see, then they can squawk about why it works.

    Well, I guess it's true then, I am very stupid and this person is obviously highly intelligent.

    Funny, folks said that before when I added PO4 to my tank well over 1ppm and high traces and used tap water and used 30ppm of CO2 and suggested not using test kits and how to cure most species of noxious algae...........

    I'm glad I am on the other side of the fence, as long as it's the right side. I have a great deal of practial experience and approaches to this, not all science, many seem to forget that. I'd rather be right than going with the flow.

    So Jay, what do you think about the method?
    Not the theory etc, but the practical aspects?
    Do you think it's helped and would be helpful to others?

    I do and it's not some small subtle thing either.
    I'm still getting data and set up for the experiment.
    Hopefully I'll have it done this weekend.



    Regards,
    Tom Barr
     
  18. reiverix

    reiverix Lifetime Members
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    Re: CO2 issues? Read this

    Tom, does the surface of your tank water build up with tiny bubbles? I mean millions of them. I feel like I'm suffocating the tank but everything seems fine.
     
  19. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Still think I'm full of crap?

    If it's wasteful, why does it work better?
    I saw the same drop in a 180 gal tank's reactor when we put a venturi loop on it.

    Pearling occurred in 1 hour instead of 3-4.
    pH went from 6.4 to 6.1

    No other changes, no flow differences etc since it's a sump reactor.

    I keep telling folks like I did with PO4 and eventually it too shall come to past.

    Regards,
    Tom Barr
     
  20. matpat

    matpat Prolific Poster

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    Re: CO2 issues? Read this

    Nah, only about 3/4 full. If you were full of crap you'd have brown eyes ;)

    I think the only way it is wasteful is if you don't throttle back the CO2 since this is obvoiusly a more efficient way of dissolving the CO2. I am referencing my use of the Kent Turbo Venturi valve on the input of my external reactor. This of course assumes you have optimal growth ( which few of us do) before you do the modification! I have yet to try the diffusor method but I'm not sure I will given the results I got with the Turbo venturi. Similar cost for the turbo venturi as the diffusor.

    I also made one of your powerhead venturi reactors for my 30g tank. It is giving me similar results. Riccia pearls in about an hour and actually floats the driftwood to the top of the tank. Granted, it is a small piece of driftwood but it is still pretty cool. Pretty good for two 36" ODNO flourescent tubes without reflectors! I never got those results from my external reactor.

    The Rotala sp. "Vietnam" is literally covered in bubbles halfway through the photo period now. Never pearled that much before your venturi reactor was added! It looks like it's covered in snow...might make a nice Christmas type scape when that time of year gets here :)

    It definately drops the CO2 faster with the Kent's Turbo Venturi added to the input of the reactor. The Turbo venturi also kept the CO2 levels up by itself while the reactor was off of the tank for several hours while I made a venturi loop and waited for the Epoxy to dry. If my pump wasn't so loud, I probably would've left the reactor off of the tank!

    I think folks just need to give these things a try and prove it to themselves! You can read all you want about something, but until you do as Nike says and "Just Do It" you'll never really know...the Diffusors, Turbo Venturi, and powerhead/viewtainer, are small investments compared to how much most of us already have in our tanks!
     
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