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Confused on CO2 mist

Discussion in 'Advanced Strategies and Fertilization' started by jrneuzil, Dec 25, 2005.

  1. jrneuzil

    jrneuzil Expired Subscriber

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    Ok, I have spent the last two days reading many threads on Misting. Maybe that is my problem, I read too much and am now a little confused. I am willing to try mist but don't get the how. I see the info on the sweetwater stones, so If I get one of those, then what ?
    Do I put it at the end of a CO2 line in the tank and mist away right in the tank?. So maybe in or near the intake of my Eheim.

    Or do I put the sweetwater stone at the end of the CO2 line inside my external reactor.

    Sorry if this has been covered before, but I keep missing it.

    Thanks,

    JR
     
  2. Cornhusker

    Cornhusker Guru Class Expert

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    Re: Confused on CO2 mist

    if you are going to use the sweetwater stone hook to co2 supply line and set on bottom back of tank.you can turn your spraybar so outlet water blows down back of tank or set spraybar vertical and set stone at bottom edge of spraybar. small bubbles will be blown around tank.distribution of co2 is very effeciant using this method. also you will need a powerhead of some kind just below surface to get surface motion.a solonoid is needed to turn gas on and off with light cycle.if you can use a digital ph meter and try for a 6.4 reading within a few hours before lights go out.i'm allways experimenting with co2 distribution and i've found this method to be the faster and more consistant way.the bubbles blowing around the tank may not be to everyones liking,so to each his own.like ''MIKEE'' says,try it you'll like it! regards,cornhusker :) :)
     
  3. jrneuzil

    jrneuzil Expired Subscriber

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    Re: Confused on CO2 mist

    Would there be any advantage or maybe more C02 absorption if the Sweetwater stone was placed inside an outside reactor. My thinking is if both would increase efficiency.
     
  4. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    CO2 mist is not about dissolving efficiency, it's actually counter to that.
    That is part of the controversy for many.

    It's about delivery of pure or near pure CO2 gas to the plants directly, rather than adding very diluted 30ppm in a thick visicous medium, water.

    Even if a pure gas bubble hits the plant leaf once every 5 minutes, that's still far more than the 30ppm in the water and the rate of diffusion is much more rapid into the plant.

    It's very tough to prove that the CO2 that enters the plant is CO2 dissolved in water or in the gas phase. I'm not sure how to show that, so I'm not even going to touch that quagmire but I know another way:

    So rather than that method, I've approached it from a O2 plant production as a measure of increased growth. You can measure the CO2 ppm levels in any two tanks for comparisons. So if they are close, then the mist is the main variable. You can even do something like this in a tank, see how well the plants grow near the mist outlet without blasting the mist all around the tank.

    This is pretty damn clear data and folks can visually see the difference when done right.

    Folks that claim it does not work or that I'm nuts simply have not tried this approach nor looked at the pearling and O2 level difference.

    It's plain as day. I doubt I can prove the gas vs the liquid gets to the plants better, but I can show it does produce better growth.
    Some folks have added the mist to a reactor, that works also, but.......you should simply use the venturi reactor is that is your goal, cheaper, simpler etc.

    Does essentially the same type of thing.

    Regards,
    Tom Barr
     
  5. jrneuzil

    jrneuzil Expired Subscriber

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    Re: Confused on CO2 mist

    Tom,
    Thanks for the reply. I would like to keep the reactor out of the tank. One thing I was think of was building a small housing to hold the sweetwater stone that was connected in line with the output of my canister filter. I would then be spraying the mist out the spray bar into the tank.
    Would that accomplish the same thing, or no.
    I was thinking of three or four inches of clear PCV, hose barbs on each end with a CO2 line misting the stone inside.

    JR
     
  6. wapfish

    wapfish Prolific Poster

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    Re: Confused on CO2 mist

    Tom, this is a crazy thought, but maybe it might work. Do you think some sort of fine mesh netting could be used to physically exclude bubbles from contacting a particular set of plants in a tank? An identical set of plants in the same tank could then be left exposed to the bubbles. As long as the latter grew at the expected rate for plants using strictly dissolved CO2, it would be an acceptable control. The visuals would be pretty dramatic.
     
  7. wapfish

    wapfish Prolific Poster

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    Re: Confused on CO2 mist

    Oops! Said that sort of backward :eek:

    As long as plants INSIDE the mesh grew at least as fast as in a non-mist tank, it would be an acceptable expt.

    Perhaps the netting might limit diffusion too much though and the water inside the netting would become depleted? Could the right size netting be found?
     
  8. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    Sure, that works, I use the stone at the bottom rear and have the spray bar vertically mounted so the mist gets blasted with hardly any view of it in the tank.

    Regards,
    Tom Barr.
     
  9. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    I know what you are saying, but how small do these bubbles need to be thus how small does the mesh need to be?

    You'd need similar flow rates, but something could be done perhaps.
    I'd rather stick with the O2 levels.

    That does not lie and also relative growth rates do not either.
    No hobbyists have even done RGR's for our plants when comparing a method etc also.

    It's not that hard either.

    REgards,
    Tom Barr
     
  10. wapfish

    wapfish Prolific Poster

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    Re: Confused on CO2 mist

    You're right. Monitoring RGRs and CO2 levels is a more straightforward and reliable way to put a foundation under the mist story. It will definitely serve to establish the "better growth with mist" aspect beyond anecdotal claims.

    A slight twist (if possible) might be to run the comparison so that CO2 ppm averages somewhat higher in the tank without the mist. Given equal or better growth in the tank with the mist but with lower CO2 ppm, the take-home message will be even stronger.
     
  11. phineus

    phineus Junior Poster

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    Re: Confused on CO2 mist

    It is ok to put a CO2 line directly into the venturi on an in-tank powerhead, correct?
     
  12. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    Yes, the preferred method.

    Regards,
    Tom Barr
     
  13. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    The claims on either side will not be resolved by chasing bubbles and monitoring gas.

    I've used the mist to successfully grow marine plants using air alone.
    No reason why this would not also work here with pure CO2 gas.

    Mist and the measured CO2 level(even if it's not absolute, eg the real CO2 levels, you only need a pH before and after) should be kept close together as far as pH.

    Several species of fast growing plants should be used.

    The O2 levels alone and pH can give you all the info needed, but the RGR's would back it up pretty good also.


    Regards,
    Tom Barr
     
  14. FrankG

    FrankG Junior Poster

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    Re: Confused on CO2 mist

    Tom,

    That could be a hard requirement to meet. I would assume that after a while the mist bubbles will consist not only of CO2, but will reflect the relationship of the dissolved gases in the water column due to the diffusion that takes place. Therefore, some of the CO2 will dissolve in the water column, but at the same time oxygen and possibly a small amount of other dissolved gases will enter the mist bubble from the water column.

    That does not change the fact that with this method, submersed plants have access to CO2 gas and dissolved CO2. And based on my personal observations, I can confirm that growth is phenomenal.

    Regards,
    Frank
     
  15. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    Well yep, the rate of diffusion is very limited due to the transfer of the liquid solution to a gas state, so the notion that other gases diffuse into the bubble is not a very strong arguement.

    Recall that the diffusion from gas to the water is roughly 10,000 times slower, now reverse this the other direction(the rate constant should still be the same as well as the boundary layer thickness/distance). The rate would be very slow, which is why they use aerators, O2 injection, wet drys etc.........to degas the water, rather than having it occur instanteously due to diffusion of partial pressures alone..........

    Degassing into the air above(or INTO the bubble) is not a fast process either.
    Funny how naysayers are on a one way street.

    If the CO2 is 10X higher in the water, more CO2 will tranfer into the bubble also. So even if the all the gas in solution is the same as the bubble, you still have a much fast rate of transfer in the gas form versus the dissolved water form.

    No?

    I mean let us accept the naysayer's arguement.
    Assume that all the gas in the water and the bubbles are in equilibrium.
    Assume it occurs instantly(we know this does not happen, but let us assume for a moment to indulge them even more).

    Since the gas is still at 10X higher CO2 levels, the issue now is if the gas vs the liquid forms diffuse faster correct?

    Now we know the diffusion constants for gases vs water, they are about 10,000x faster.

    So the plant still gets the CO2 at a much faster delievery rate, even if the concentration is the same.

    I'd rather breath Gas than a thick heavy liquid, plants and diffusion are no different.

    But now if you go back and add that extra CO2 left in the bubble, now you can add that concentrational difference back into Fick's 1st aw.

    Still, 3000ppm in gas solution of CO2 is pretty juicy.
    And that is at equilibrium.

    Adding 1,000,000ppm of pure CO2(or nearly pure) into the gas, will really get it going.

    Even if the bubble lost 90%, what about the 100,000ppm?
    And why doesn't those little mist bubbles persist when they rise? We can watch them disappear, so there is not a lot diffusing into something that's disappearing either.

    You cannot have both on that issue.

    Blah, I'm going back to RGR, and O2 levels:) :gw :gw

    It revolves around fick's law, but I'll let some physicst mess with it that likes micro bubbles in solution, I'm more interested in better aquatic plant health.

    As you and most anyone that has tried it can attest, our eyes are not lying, nor are our plants. That's growth and you can see the dramatic pearling.

    Once you see this and see that you can maintain that pearling all week long, you know something has to be causing the growth.

    Adding CO2 in this manner has to provide the plant something, even if the naysayers claim otherwise, they can not disprove nor prove what they are saying, merely add doubt, that's not much use.

    I tried to approach the gas bubbles in larger terms, but that is not the same as a micro bubble unfortunatly. It really does require some techincal equipment.

    Regards,
    Tom Barr
     
  16. Cornhusker

    Cornhusker Guru Class Expert

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    Re: Confused on CO2 mist

    Tom, is not something that works better,more effeciant?regards,cornhusker :) :)
     
  17. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    But it does seem obvious it is not more efficient, you can see bubbles being wasted and floating around up to the surface some.

    Regards,
    Tom Barr
     
  18. Cornhusker

    Cornhusker Guru Class Expert

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    Re: Confused on CO2 mist

    Tom,I STAND CORRECTED! HAPPY NEW YEAR! regards,corn :) :)
     
  19. Tom Barr

    Tom Barr Founder
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    Re: Confused on CO2 mist

    Well, there are some engineering studies on micro bubbles in ocean systems, not a simple model to say the least.
    It's beyond what I am willing to get involved in directly.

    Rather, I am going to address it on a more practical method, the plants are the test kit.

    What might seem efficient, might be less so and what might seen less, maybe more.

    Hard to say, but assumptions really will get you into trouble if you assume too much and accept previaling dogma.

    That is road I've been down many times.

    It's been a mud fest here in CA, been working to dig stuff out.
    We are not waiting for FEMA here:)

    Regards,
    Tom Barr
     
  20. Crazymidwesterner

    Crazymidwesterner Guru Class Expert

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    I know this is an old thread but I was wondering is anyone using the mist method with a sweet water stone under their filter output? I was curious if I was to use a 20 lbs co2 tank with this method on a 75 gallon tank how long do you think it would be before I needed to refill my Co2. I'm just doing a bit of a cost analysis.

    Thank You in Advance,
     
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