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CO2 issues? Read this

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

  1. fishface

    fishface Guest

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    Re: CO2 issues? Read this

    matpat, how exactly does the turbo venturi work and do you have a picture of the configuration?
     
  2. Jay

    Jay Lifetime Charter Member
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    Re: CO2 issues? Read this


    I see what I see, there has been a dramatic improvement in my tank, and I had thought it looked good before I started experimenting. The CO2 misting was the only change in my fert routine.

    The downside is the verbal abuse by strangers when you try to explain it to them. :rolleyes:

    Jay
     
  3. matpat

    matpat Prolific Poster

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    Re: CO2 issues? Read this

    Here are three quick pics of the Kent Tubro Venturi. The first pic is of the venturi itself. The CO2 input is on the Tubro Venturi.

    The second pic is how I set it up in the micro misting mode using a Quiet One 1200 pump (~300gph at 0" head). Intake is at the lower right of the pump and the output is at the top of the venturi. It produces a fine mist of bubbles and since the pump's flow is adjutable it can be set to send the bubbles all around the tank or just up the back of the tank into the flow of the filter. with some flow rate adjusting.

    The third pic is how I have it set up on a 1 1/2" diameter DIY PVC reactor similar in design to the "Ghori" reactor with a "Barr" venturi. This was designed for a lower flow canister (Eheim ECCO 2234) and is a trial that has not been in a tank yet. The reactor is designed to be used vertically underneath the tank. The input is on the right side (top) of the pic and the output is on the left (bottom) of the pic. The "venturi" hose is about 2" down from the top of the reactor and is connected to the output side of the reactor. Hopefully this will discharge any undissolved gasses from inside the reactor to the output side of the reactor. I may move it farther down the reactor if needed once I install it on the tank and let it run for a couple of days.

    In my 75g the Kent Turbo Venturi was on a 2" diameter clear PVC reactor Without any bioballs inside. This was connected to a Magnum 350 filled with bioballs so hopefully the flow is close to the advertised 350gph. This allowed me to see how the bubbles were "misted" into the reactor and disolved fairly fast. I spent a whole afternoon playing with the venturi and clear reactor watching it dissolve CO2 and drop my pH.

    Here is a link to Bernoulli's Principle along with an animation for venturi design that is pretty easy for us "common folk" to understand.

    http://home.earthlink.net/~mmc1919/venturi.html

    There are also a couple of mpegs on the advanced discussion page. I didn't understand the physics, algebra and calculus much but the mpegs help explain it a little bit better, at least for me :)

    ktv.jpg

    ktvpump.jpg

    ktvrector.jpg
     
  4. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    The venturi loop needs to be placed further down, about 1/2 down the reactor tube housing.

    You can feed the venturi loop back into the intake side of the Quiet one pump also rather the outflow from the reactor or you can feed the gas into the Kent venturi with a Tee from the main CO2 gas line.

    In any event, you can see that there are many options here and these loops and venturis do help decrease the pH better than without.

    This also extends out to the CO2 misting idea as well.

    Whether or not you agree with anything I've said, this method will improve CO2 utilization and improve growth if you actually try it.

    And this type of work specifically on CO2 will generally do much more than anything with NO3/K etc and subtle nutrient issues.

    So it's not time wasted....nor cost much to play around with.

    Regards,
    Tom Barr
     
  5. Cornhusker

    Cornhusker Guru Class Expert

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    Re: CO2 issues? Read this

    :) tom,i was at our city hospital the other day and they have a 200 gal salt tank. i noticed a tube at the back of tank blowing out tiny mistlike bubbles that circulate around the tank.looks like a beautiful way to work on freshwater tanks. i don't know much about salt tanks,would something like this work with co2?the mist idea is a very good one. i have tryed it many times in the past but then using yeast ,cant get enough pressure to get mist going.right now i have a small pump below the reactor blowing what comes out over the tank. it works fairly good.someone should have a ceramic stone of about 2"x 8" to fit nicely at back of tank that is very inexpensive.a person should use some kind of a bubble counter and solonoid with stone idea,right? regards,cornhusker :) :)
     
  6. alexperez

    alexperez Prolific Poster

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    Re: CO2 issues? Read this

    I got my 2 small Azoo diffusers yesterday and hooked them up. I placed the diffusers in the path of the water flow(2 lily pipes on oppisite ends, each being driven by an XP3 Filter). The tank started to get filled up with lots of micro bubbles pretty quickly. I kept every thing else the same so the only difference was the use of the 2 diffusers instead of the External Reactor.

    It was running for a few hours (6-9pm) but I did notice the pearling pick up
    a lot. I had just done a triming 2 days ago and the stream of bubbles from the damaged parts of the plants went from a steady stream of bubbles to a fast stream of bubbles.

    Now to keep an eye on it for a week or 2 and see how the plants react.
     
  7. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    So based on your and now quite a few other folks, what is your opinion?

    If you keep the same CO2 rate and assumed that all of the gas was being diffused in the reactor, how can you get better growth(eg more pearling and other obvious signs of better tank health) without it being the CO2 delivery in the form of a gas vs dissolved?

    You can see after about 1-2 hours the gas mist is far more prevalent and the plants start to pearl sooner in the day(1-2 hours after the lights come on) and if you measure the O2 levels, the O2 is also much higher.

    Folks have said I'm wrong (I'm not:) but you can see the observations, you can test it yourself and then see if you think those bubbles are really some other gas(they aren't) and the other issue=> there is no research on this issue. That is what I am doing right now and ruling out each issue step wise and building support for the theory.

    In the meantime, folks have reported better growth, more pearling, less algae using this method.

    So whether you agree yet or even care about that, you can still try this and see how well it works.

    My data and method looks very good and supports the theory at every turn so far. I should finish and get it out later this weekend.

    Regards,
    Tom Barr
     
  8. reiverix

    reiverix Lifetime Members
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    Re: CO2 issues? Read this

    What can I say. Based on this technique it means my bolbitis is actually pearling. Seems too good to be true but I can't deny my eyesight. My anubias doesn't pearl, which to me anyway, means it must be true pearling on the bolbitis. If it was just O2 bubbles then they should be covering the anubias also. Does this make sense?
     
  9. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Yes it does, it's rare to see Anubias pearl but I've had them do it but mainly late in the day, Bolbitus I've had pearl like mad.

    Also, Bolbitus is a very covetted plant and slow growing in most tanks, but I grew it like mad in my 55 for several years using the internal CO2 reactors on this site and they always [pearled like mad and grew very fast.

    Growth = better growth than merely pearling alone without the associated growth that goes with higher rates of photosynthesis.

    With time, folks can see the increased growth and you can also measure the O2 levels of the method vs dissolved alone.

    Regards,
    Tom Barr
     
  10. reiverix

    reiverix Lifetime Members
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    Re: CO2 issues? Read this

    My bolbitis was a slow grower until I added a powerhead to give some flow around it. It exploded into life after that and I actually had to end up selling some. Never thought I'd see the day when I had too much of the stuff. LFS paid quite well for it too :) If my anubias start pearling my heart may stop.
     
  11. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    You can grow Anubias very easily emergent.
    Mine does grow well submersed though.

    Bolbitus will always be in high demand at the LFS making it a good trade species.
    It's also a nice dark cool color that makes many species of fish look nicer.


    Regards,
    Tom Barr
     
  12. IUnknown

    IUnknown Lifetime Members

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    Re: CO2 issues? Read this

    Tom ran into this old post tonight. Didn't seem to make sense to me, so I was wondering if you had any updated insite to the reactor vs. diffuser issue. If the plants maximume uptake for Co2 is 30 ppm why would it matter if it comes from liquid or gas? When you say more oxygen, was this measured, or just eyeballed from the bubbles. how would you tell the differnence between Co2 bubbles falling on leaves and O2 pearling?
     
  13. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    DO meters work great for deteriming the difference in growth via plant production, it's the standard in aquatic biology.....

    So the pearls are not we measure directly, it's the actual O2 in the water.

    For this to work that way I've described, sense or not, the O2 levels much higher and the CO2 relatively the same based on the water's pH/KH.

    The tank replicates with higher O2 may have lower CO2ppm, but not the reverse.

    The hypothese is that tanks with CO2 mist will have a higher rate of plant growth(and production of O2 which is easily measured) than tanks without (everything else being provided on equal terms, eg dissolved CO2).

    You can run the mist around the tank real good, then determine a relative CO2 ppm.

    Next, try the 100% dissolved in the reactor at the same CO2 ppms and measure the O2.

    You need a control for each test and relatively similar plant biomass/species etc.

    I'm busy killing weeds and making huge tanks at the moment.

    Watch the bubbles float around sometime from a diffuser. See how long they persist. CO2 does not dissolve instantly.

    Even if mixed with other gases, the CO2 is expelled at a much higher concentration than the measly 30ppm.

    So the CO2 can diffuse rapidly as a gas into plant, much faster than as a liquid [aq] phase.

    Even at 380ppm that is typical air concentrations, and the rapid diffusion in air, we see enhanced growth of plants at 1500ppm.

    You can see visibly the growth and pearling difference in your tank.
    I'll get around to testing it and see what I can figure out miore clearly and look into it more.

    Might be awhile still, but heck, no one else does these types things so there's no pressing rush either.

    Regards,
    Tom Barr
     
  14. IUnknown

    IUnknown Lifetime Members

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    Re: CO2 issues? Read this

    Tom wrote:
    "The only way to add more than 100% ambient levels is through plant production."

    What about injecting O2? I still have to read most of the other threads on this subject but was curious as to the conclusion of the "Co2 actaully being O2 bubbles" issue. It seems like the best way to disprove that would be to run the diffusser in a tank without plants (maybe this was done?). If the DO meter measures an increase in Oxygen levels then this would show that the Co2 bubbles are actually being filled up by O2 as the Co2 diffusses out. The idea is that the Co2 bubbles would be sucking Oxygen from the surface of the tank to over saturate the tank(were else would the O2 come from?). This would explain why the bubbles persist more later in the day as the tank is saturated with O2.

    The other issue that I'm not convinced about is 30ppm being saturated enough to slow down the rate of diffussion. This thread did a pretty good job of disproving that idea,"CO2 Solubility Experiment - Photos, Video.....Evidence! " . I guess you could connect a ph meter to a computer to see if the absorption rate changes at all. If it doesn't the Co2 would be a line in a ph vs time chart. It would be a bell curve if 30 ppm slowed down the saturation rate.

    I've got a difusser in the mail to see how things improve. Regardless of whats actually happening the extra O2 is good for feeding bacteria, etc. Interesting stuff, I'm glad you have a thick enough skin to deal with all the attacks Tom, the hobby would not be going anywhere otherwise.
     
  15. Tom Barr

    Tom Barr Founder
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    Well yea, but I'm the only person that seems to have done so to date.
    Going back about 4 years ago.

    Well I can tell you this much, they are wrong unless the bubbles rise up from the plant. O2 would have to cross that boundary layer, much like the slowed rate of diffusion from the surface layer intereface.

    You know..........just like why the gas exchange rate is 10,000 times slower in liquid and air? That goes out the window when these same folks want to argue in favor of O2. CO23 will go into solution fast, but not one of these folks shows how CO2 and O2 goes _out of solution_ and into a gas phase.

    That is key since they claim that the gas in the bubble changes rapidly.
    they claim it changes from CO2 in a few seconds (some suggest instenanous!) to O2 or N2 gas.

    But it takes time for the gas to come out of solution and into the microbubble.

    As that time passes, the area, the boundary layer around a apheron will have a higher level of CO2 than the water adjacent to it.
    That's the other part they have not considered.

    A micro pH probe could show this.
    I might be able to get one at the lab.


    I've run diffusers in tanks without plants, I was studying algae growth responses to CO2 and O2 at elevated levels.

    I don't think there is enough O2 removal to detect anything significant if this occurs, which I don't think it is.

    But the video shows nothing about what the gas is actually.
    you andf everyone esle that's kept plants over the years have seen the increase time the CO2 microbubbles persist later in the day, these are not from plants, you can place the CO2 ADA diffuser right out in front, have the current blasting the mist around and see this over and over again.

    The video does not address the microbubble, it does address the CO2 in a reactor tube which is a different case.

    There's a simple thing, I know they are wrong, so I don't care as long as the attacks are not personal.

    I'm not particularly certain what the gas is yet in the reactor tubes as they build up over time, but I can find out what it is made up of.

    Thing is, no one esle will ever do that.
    I ask folks to, but they are more interested in arguing Tom Barr is wrong than actually engauging in doing any work. At least Ted did some work and put it up on the web. :p Which is a lot more than I can say for others.

    I have some other thing I haver tio do and finish up before I can get to that question just yet, but for now, a simple DO meter and the treatement/control will tell you if the plants grow faster or not with the method.

    I'm not so sure about Ted's trail either.
    I want to go back and make very sure this is actually the case.

    I tested O2 in the reactor tubes much like Ted did for CO2 and O2 does not dissolve anywhere near the same rate, O2 and N2 are very insoluble in water.
    These are the two best candidates for the other gases.

    Ted did not test O2, I did.

    So that's one gas in the reactor tubes we can rule out.
    I have N2 at work, so I can test that one also but it's very insoluble and we can predict the rate it dissolves.

    Now what about knocking N2 and O2 out of solution?
    This is different than getting them to dissolve.

    Reactors, unlike diffuser stones, have what precisely?
    Generally they have a place for the bubbles to degas.

    They have those bioball media which are designed for high flow degassing. This degases and then reabsorbs again.

    But............I also see the gas form in my internal CO2 reactors which have no such degassing media of any sort.

    The large bubble forms daily.
    With or without the venturi running also.

    The gas is purged also due to the burp holes in the side.
    So it's not all build up like in the in line versions.

    Why would the gas in a solution degas there and not else where?

    There is a lot of unknowns so far and the results from the O2 meter suggest there is something to this and we can watch those microbubbles, folks can speculate that they are no longer CO2, but not one of those folks will ever get around to showing it is or is not with any certainly.

    I cannot say that O2 will dissolve that fast into a microbubble, nor N2.
    CO2 does dissolve much faster than either of these gases. It has to go across a gas/liquid boundary layer to do so, same with CO2.
    So I cannot see how these rates can be the same, we can watch the micro bubbles come right out of the disc that we know is 100% CO2 and they don't disappear.

    Apparently when the shoe is on the other foot....now they do not respond........funny how that works.:rolleyes:

    Regards,
    Tom Barr
     
  16. Professor Myers

    Professor Myers Guru Class Expert

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    "It is an issue of delivery and in what concentration(100% CO2 gas)."

    I'd like to test the purged false gas to identify the waste components, but I'm guessing that would vary depending on individual water chemistry so it may be a mute point ...?

    The larger point being that the waste gas needs to be cycled out !

    I also wonder if the ambient Co2 micro bubbles degassing aids in a better o2 balance ???

    Mi Dos Centavos, Prof M
     
  17. Tom Barr

    Tom Barr Founder
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    Well a micro bubble of air, pure air, will presist a long time, it's mostly O2 and N2 gas, but there's CO2 in the bubble as well.

    For a bubble to presist at it's stable concentration and not degas into solution, the solution and the apheron must be in equilibrium.

    Partial pressures in the apheron microbubble = partial pressures of the solution gases.

    So what I stated orginally was that the CO2 gas would presist longer in a solution that is 30ppm vs 3 ppm.

    The microbubble will have 30ppm at least(or more being time dependant) and an air bubble will only have 1-3ppm CO2 depending on the ambient levels.

    The micro bubble that is not dissolved will have a higher concentration of CO2 than tank water that is 3 ppm of CO2 vs 30ppm.

    I think this is much more along the lines what I meant to say to begin with and gets around some of the problems I had eailer with the dissolving rate.

    The rate is still the same, depending on the KH, but the end point is different.

    The micro bubble is left with 30ppm (end of day) vs 0-3ppm (start of adding CO2 during the day).

    The other issue is flux due to the boundary layer(bubbles bob right through those well) and the flux coefffiecent is 10,000X faster for a gas than a liquid.

    So even if the microbubble equilibrates with it's surrounding water, it's still better at delievry of the CO2 gas to the plant.

    Later in the day, the CO2 microbubbles will become higher or at least = to the surrounding water which by then is 30-40ppm CO2.

    Regards,
    Tom Barr
     
  18. ringram

    ringram Junior Poster

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    Tom,
    I should have read this ages ago. When I saw you in person about a year ago, you showed me that diffuser disk to give a very fine mist and I should have just used it right then and there. Instead, I made a PVC reactor and while I'm getting Co2 mixed into the water, I didn't realize that the plants can't use it as easily. That would explain why I've been constantly battling different kinds of algae, particularly green spot on plant leaves and glass. Furthermore, some plants just won't grow and simply wither away and die. All this while my Co2 levels are testing good (ph - 6.4, 5 DKh), which apparently is more of a false-positive.
    Are you saying to add a diffuser disk in conjunction with an inline reactor, or instead of? Is it just a simple airstone disk that you would find at the LFS, or something else? With the amount of lighting that I have and the amount of ferts that I add (EI), I'm now convinced that this was my problem. That's what I get for not heeding your advice!
     
  19. Tom Barr

    Tom Barr Founder
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    I think I am closing in on the reasoning why this works better and it also shows why the ADA products, particularly the misting amplifies the growth of his tanks so well.

    I did not think about the theory I presented about "mist" but it would lend credence to the notion of less CO2 but higher growth using mist.

    You can try either methods, a hybrid reactor/disc or pure disc.
    I use venturis/disc and disc and reactors and disc methods.

    I think over all the venturis/disc work best, but these are better suited for large tanks.

    Small tanks, the disc alone, larger tanks: reactors.

    I will say the Aquatic magic disc I recently got: WOW!!
    great product, like the ADA beetles except 5x cheaper.

    See ebay site.

    BTW, I'm redoing the Albany Aquarium for Guy this Sat.
    I'll be using the AM disc.

    Should be fun, I'll use the African root for the hardscape.
    Oddly, I've never used this wood in any scape.


    Prof M, did you test the Gas that's purged?
    I'm lacking time and other things at the moment and will not get to it.
    It is one of the great mystries yet no one has ever tested what it might be.
    I'm thinking O2 and N2 mainly.

    Regards,
    Tom Barr
     
  20. reiverix

    reiverix Lifetime Members
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    Using the mist method, my plants definitely pearl better with good circulation. I noticed this after giving my 75g jungle an overhaul and making it a bit more manageable. Purple cabomba and rotala magenta was pearling so much I could barely make out the leaves. Quite a sight.

    So as an experiment I waited until CO2 switched off and let all the microbubbles from the diffuser fizz out. So now the only bubbles in the tank were true pearling. I gently shook the cabomba and a few other plants to clear them of bubbles. Well after 10 minutes it was bubble city once again. Hardly scientific but I think I can conclude that it was true pearling and not microbubbles from the mist method landing on the plants.
     
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