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CO2 issues? Read this

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

  1. Tom Barr

    Tom Barr Founder
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    CO2 is one of those critical things that aquatic plants folks should really focus on.
    I've nagged folks about this for a very long time, and I will likely nag you to the grave.
    Complacent experts, newbies, test kit freaks, all of you(and myself included).
    Poor CO2 reduces growth and is responsible for nearly 95% of all algae related issues.

    Now KH test kit variance is one issue, making a reference standard to compare you KH test to is a very WISE idea to check the accuracy. I've seen many folks have very high CO2 predicted levels, yet fish were fine, but another than has barely 30ppm and the fish are gasping. It cannot be that both are at the same CO2ppm level becaused we would expect to see the same behavior from the fish. Instead we see very wide ranges and impacts on the fish(as well as plants).

    So it's much more likely that it is the testing method, rather than anything else.
    pH is the best thing as far as accuracy for CO2 measurements using a pH probe and no electrical equipment runnign when the pH is measured(stray current will depress the pH giving false high ppm CO2 levels).

    KH test kits have consistency issues (see recent post) and in some places, although rare, non bicarbonate alkalinity exists(recent poster in NM has significant borate alkalinity, desert regions generally).

    Addressing this issue by making a reference sample will take care of the KH issue.

    The next issue is more interesting for many of of you.
    I'd suggested that the venturi DIY reactor I have shown folks on my site is better than any reactor. Well, initially, and perhaps partially true, is the purpging effect of gas build up.
    This gas is some O2 and some CO2, but very little "air".

    As the gas is expelled, consistently I see better growth, this is not due to O2.
    So why would a mist of tiny CO2 bubbles vs dissolved CO2 in solution do better for growing plants?

    I addressed the O2 issue simply, I used a diffuser disk for CO2(no O2 gas build up occurs).
    But that did not do it __alone__.

    I wondered why.

    So I placed the diffuser disc near similar current like that produced by the venturi reactor after is starts mistuing the gas out the bottom.

    Lo and behold, Bam! Excellent similar growth.
    Not the kind of so so growth, but pearling like nothing you have ever seen or perhaps only in a very few well run tanks right after a water change. But I'd not done a water change for a week.
    I tried it several times on 4 tanks, same result in each tank. Day after day, intense pearling even with fair good current.

    So why would this mist be better than dissolved CO2?

    For one thing, it's __pure CO2 gas__, which flows much faster than dissolved CO2 liquid.
    The flux rate is much faster with pure CO2 gas than CO2 dissolved in water, so the plants get more CO2 and a more concentrated form.

    Some folks may not like the bubbles, some might not like pearling.
    But I sure do.

    I can say that the venturi effect is one of CO2 now, and not of O2 by using the diffuser disc to rule out O2.

    So that just left CO2 and the gas vs dissolved form to consider why one method was better in terms of plant than another.

    Both flow and actually having some gas in the tank itself seems to be the key here.
    So those disc are not so bad and neither are the venturi reactors.

    You can make a purge loop for external reactors by making a hole 1/2 down and running the air line back to the intake for the power head, caniter filter etc, this will not add bubbles but will reduce the gas build up inside the reactor.

    The real issue is having gas bubbles in the tank and putting them where the plants are in that form.

    I think folks should really consider this/these idea/s and try them.
    I've had very intense pearling and have over the entire routine time frame, not just for a day or a few days.

    Be careful and watch the fish, CO2 levels when doing this, I've not had any fish issues yet. Make sure there is some surface movement. If you use disc, clean them often(monthly).

    For larger tanks, they make 6x1" diffuser stones for about 60$ than can be used set along the bottom back gravel layer so they will not be seen. wwww.aquaticeco.com sells them if interested.

    In any event, this notion of having tiny gas bubbles floating around very dissolved CO2 might solve many folk's problems and improve those who seek better growth.

    Nitrogen is an essential element, but only 1.5%, vs 40+ % for Carbon, it is very very wise to focus on this if you seek better growth.

    With good CO2 levels, even the wimpy plants do very well(Tonia, ES, Eirocauleon) algae dies, pearling as intense as you have ever seen it day after day will occur.

    I think the gas bubbles might also be less of an issue for fish since it's not dissolved into solution also.

    The nutrients can be addressed easily by doing EI, so you know there's enough, so all that's left to really focus on is the CO2.

    So I have been playing around trying to figuire out a good way to reproduce max CO2 without causing issues for fish, and adding enough for the plants.

    The CO2 mist + current seems to be the best method.

    This can be done with a reactor or a diffuser stone/disc.

    Also, folks using spray bars, turn them vertically, next to the intake and place the disc down near this also. This hides the bar, the disc, intake all in one place. Having the spray bar current blowing along the back side the tank wall seems to give good flow characteristics+ near the disc, the water blows out and away from the intake and circles around to the intake.
    Since water is being blown directly away from the intake, this gives optimum mixing.
    Since water is being blown directly on top of the difusser, all the bubble mist is being blown all over the tank.

    The results are easy to see.

    The other issue is not to trust the test kits so much until you see the type of pearling like this, no BBA growth etc, slowly and patiently add more CO2 till you get the pearling and good growth. Basically use the test to get close, then tweak(add more) carefully and slowly.
    Do not go overboard, do it slowly and observe the plants/fish. Your test may give you high numbers, but if the fish are fine, then it's okay.
    Turing off CO2 at night will help add the margin of safety also. We add CO2 for the plants, not to maintain pH. Some leave it 24/7, but mainly out of convenience rather than methodology. With disc, running them at night can cause issues, anyway, you can save 2-3x the gas by not running it at night. We know fish don't care about the pH change.


    Regards,
    Tom Barr

    www.BarrReport.com
     
  2. rrguymon

    rrguymon Prolific Poster

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  3. CrownMan

    CrownMan Junior Poster

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    Re: CO2 issues? Read this

    Hi Tom,

    On another board, you helped me with a non-CO2 30Long, High Light system and you were right. I floundered and last Friday, hooked up an old Aqua Medic CO2 reg, bubble counter, new PH Monitor and full tank but I didn't have a diffusser. I looked around and had an old Duetto DJ-50 inside filter that has an aerator built in on the top of the filter. I installed the CO2 hose into this, new sponges and instant CO2 diffuser that is putting out a fine mist of CO2 bubbles which then get caught in the current from my Power Head on the UG (not a RFUG unfortunately). My CO2 is at 30ppm and plants are growing like crazy. I can't tell, though, if the plants are perling or if the fine mist of bubbles is just collecting on them and then rising. Seems to work well though.

    Thanks for the Help

    Mike
     
  4. fishface

    fishface Guest

    Re: CO2 issues? Read this

    very good point here...how do you know??
     
  5. rrguymon

    rrguymon Prolific Poster

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    Re: CO2 issues? Read this

    I have been looking at the venturi you have on your DIY page. I think I can use the external reactor I made, to put on the output of my canister, in the same fashion.

    I will drill the two small holes 2" and 2.5" down on the external reactor tube. I will route the hose from the one 2" down into the venturi input to a power head in the tank and route the hose from the the one 2.5" down to spill anywhere into the tank.

    I think the top outlet might give the in tank power head a similar mist of CO2 bubbles and the bottom outlet will burb or expel any excess gas.


    Rick
     
  6. PeterGwee

    PeterGwee Lifetime Charter Member
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    Re: CO2 issues? Read this

    Tom, could it be that those bubbles "flying" out of the DIY venturi reactor are actually O2 bubbles being caught onto plant leaves and not from plant growth?

    Regards
    Peter Gwee
     
  7. TerryB

    TerryB Guest

    Re: CO2 issues? Read this

    Tom,

    There is an interesting experiment you could try along these lines. I used to work for a company that has a membrane based gas/liquid exchange technology. Been awhile since I worked for them - but using thier modules - should be able to get max CO2 concentrations into the water. There would be no mist or bubbles - its an extremely efficient diffusion reactor. I have been trying for awhile to get them to send me one (they probably won't because I am sure they think I am working for some competitor and the aquarium story is a ruse). This is the stuff used in heart lung machines for blood oxygenation/co2 removal.

    Only down sides are biofilm forming on membrane and impact on efficiency and cost. You would have to clean them after awhile possibly. Any interest? I can pursue it a little more. You would be the right guy to test since you have the "other data" as reference point and observation.

    Terry
     
  8. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Well, hehe, enter the diffuser disc, which has no such issue as a control for this same issue.

    Same observation............

    Try again:)

    Sorry Terry, biofilms and passive reactors are not my thing.
    Bioflim issue is a biggy.
    Our lungs diffuse CO2 out/O2 in through liquid(our blood) the same way as reactors do. Gas is much easier to breath in and we get far more exchange than we would with water(this can be done with super sat O2 liquid and deep sea divers etc, but you can breath much better with O2 gas!)

    Mike, see the control I used with the disc, so the answer is no, it's plant production.

    You can also do a O2 test and see if you have higher O2 levels with or without(this is what I did as well as simply observe plant health etc).

    I think this will bug folks for a long time.
    It's counter to what you woud think, since saving every last bubble seems "better" and would produce better growth, but it is an issue of delivery and in what concentration(100% CO2 gas).



    Regards,
    Tom Barr
     
  9. PeterGwee

    PeterGwee Lifetime Charter Member
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    Re: CO2 issues? Read this

    Tom, how about feeding the CO2 gas into a powerhead output with a spraybar at the bottom back area of the tank? Loads of misting around in the tank and the bubbles gets to all parts of the plants pretty good. Frankly, I did get that result some time back when you suggest that method of a powerhead with spraybar but thought those were some form of gases and not real pearling.

    Regards
    Peter Gwee
     
  10. Cornhusker

    Cornhusker Guru Class Expert

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    Re: CO2 issues? Read this

    :) tom,the issue of a staginate 55 gal tank i asked about in recent thread has responded to turning co2 way up to increase small bubbles coming out of bottom of diy reactor. also set sraybar to get surface motion. this tank has never pearled. now there is action everywhere in tank. could this be the step in the right direction? i am finding out that co2 and more co2 is the only way for a successful tank. thank you, regards,cornhusker :) :)
     
  11. jonathan11

    jonathan11 Lifetime Charter Member
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    Re: CO2 issues? Read this

    Grrr, just when I think everything is going good......Must profess my ignorance, diffuser disk- not familiar with them- could someone briefly explain what they are, perhaps name of a good one, and place to get them?
    Tried www.aquaticeco.com, couldn't seem to find that diffuser airstone- again, can someone help me out? Thx from the old geezer,

    Walter :gw :D :D
     
  12. wob

    wob Junior Poster

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    Re: CO2 issues? Read this

    Tom,
    I have a very large tank (150g, 72x24x24) and was wondering what diffusers were you looking at on aquaticeco.com? Also, do you just hook the co2 line directly to the diffusers that would be at the back of the tank?

    I have not built a CO2 reactor yet so I'm pretty flexible with trying any of these setups.

    Thanks,
    Robert
     
  13. brad

    brad Prolific Poster

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    Re: CO2 issues? Read this

    You`re a sucker for punishment Tom. :) First the po4, now co2. I will likely stick with my reactor as I can just imagine the current it would take to push those bubbles across the tank would make my plants droop that direction so......

    Anyway, kudos to you Tom for continuing to look into issues most people accept as already being researched. Even if you`re gonna get, as you would say, poo-pooed for this. :rolleyes:
     
  14. Tom Barr

    Tom Barr Founder
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    Re: CO2 issues? Read this

    Well one guy has it in for me on the APD, won't be the first time for me, probably is for him:) He's getting the ignore as he's not contributing and playing nice nor making any sense.
    He'll come around and play a more positive role later.

    Alright, CO2 diffusers for large tanks:

    This was in response to Terry Barber, who is a member here as well as a well known author of aquatic plants and writes for TFH on plants.

    Terry sez:

    >I proposed to Tom that he consider using an extremely efficient diffusion
    >device that will highly saturate the water with CO2 - but no bubbles and
    >make the comparison that way. This may actually tell more about whether the
    >presence of bubbles actually does something more.

    Already have done this and have done it with the external vs interal versions of the CO2 reactors I've made and sold to many folks here. Old stuff I have already long considered.
    I've been wondering about this for a long time. Plants do not lie and I've seen the differences between both the methods with the internal CO2 venturis vs the externals.

    I recently developed an external venturi, pretty cool.
    Knocked Mike's 180 gal CO2 problem from hell to the good range with no other adjustments by 0.3-0.4pH units. Pearling now starts about 3 -4 hours earlier. I have not gone after it with a DO meter, but he does not care, the tank is doing much better and the algae stop growing.

    I've made nearly a dozen designs over the last 12 or so years.
    I have 100% of the gas in solution that is dosed for the tanks.
    I've made all sorts of reactors from 1 gal to 2000 gallon tank sizes and tested them for effective usage(zero bubbles from the outflow and response times to pH drops).

    I've done this method for many years, many folks have, it works well when the CO2 is near 30ppm. We did not see CO2 issues till folks started adding more light(the light was not available back then generally unless you where a DIY'er or wanted to spend the $ for MH's(I did).

    My point with the gas CO2 mist, is that it definitely increased O2 levels in the tank versus the other methods. This is a standard method to measure and to quantify aquatic production(O2 evolution) in the aquatic sciences.

    While pearling/growth rates are the more "practical things" many aquarist use to see and gauge their tanks, this is a bit more clear when making comparisons about whether growth is increased using say one method vs another for CO2 injection. CO2 is also a large % of uptake and resources for the plant.

    The tank is still jamming along, everything look Riccia with the pearls, DO levels are sky high.
    No water changes yet. You do get good CO2 levels and growth and DO, but I've gotten roughly 25% more O2 using the misty bubbles method. I need to run more repetitions though. The initial results do look good.
    We'll see as time goes on.
    Folks typically are unwilling to blow 300$ or more for a DO meter.
    Some places make cheaper ones these days but they still ain't cheap. Test kit versions typically do not go beyond 10ppm but are relatively cheap.

    >I can imagine that the bubbles are providing very high CO2 levels at the
    >leaf surface where they may touch (do plants have specialized cells on their
    >surface that may just suck that CO2 right up? - I don't know...need to look
    >it up)....or that there is a very CO2 enriched water region around the
    >outside of the bubble that they similarly enjoy.

    Both.
    Since the pure gas bubble is under the leaf where most plants have their stomates, the distance is minimized. All cells take in/expel O2/CO2 etc in aquaeous form (even us in our lungs).

    The rate is determined by Fick's 1st law of diffusion.
    http://omlc.ogi.edu/classroom/ece532/class5/ficks1.html

    A distance(1), diffusivity(2) and concentrational gradient(3) are the main variables.

    1. Adding CO2 mist reduces the distances(minor/not significant)
    2. Gas vs a liquid. Clearly the gas can move faster (large factor)
    3. Increases the concentration (probably the main factor).

    These are the main mechanisms.
    No one mentioned these.

    The other issue, few folks have ever studied this notion of misty CO2 in nature.
    For all I know, I am the first to suggest it. I have never seen anything about it in the research(gas mist vs dissolved CO2 etc).

    This mist adds lots of rapid contact(even if pulsed) for the plant cells(they can store a little bit of reserve fixed CO2 and it also diffuses in the cells internally).The same is true for other nutrients. Stomates are the generalized name for the openings and guard cells are the cell types that take up CO2 and expel O2. Some aquatic plants lack stomata and guard cells, eg Hydrilla. Only one plant species (terrestrial) has none, and many of the plants we keep are amphibous(and have them).They are generally on the abaxial side of the leaf, (the underside) but Water lilies have them on the top and a few other plants have exceptions.

    The CO2 in these plants diffuses directly into the cells, they do not need to transport CO2 further since the leaves are 2 cells thick. Water lilies have floating leaves and would not do well to have them on the lower side and they do not need to worry about water loss unlike terrestrial or amphibous weeds.

    >but come up with another
    >test that can tease out what may be going on here. Certainly it's not a
    >character issue.
    >What do you think?
    >Terry Barber

    Well, there are reactors that dissolves 100%, they are available and have been for a long time(now they are much more reasonably priced). The diffusers have been as well, and the venturi design I've sold years ago and used for nearly 12 years has been around.

    The main gripe was the thing was in the tank.... even though it's more user friendly and preforms better in terms of O2 levels. I have no issue addressing the method of O2 as way to measure growth in Submersed aquatic plants or algae.

    Explaining why this occured was more elusive even though it seem like it was wasting gas was less obvious.

    Re-examining the concentration/gas phase transfer and direct absorption into the plant rather than the water first, was the answer.
    Seems weird initially.

    But so did adding PO4 way back when.
    Plants don't lie though.

    FYI, for folks interested in trying this at a larger scale:
    http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/9775/cid/2339

    These are relatively cheap and placed on the bottom of the tank's gravel (where they belong out of sight!), by placing a spray bar down low along the back wall of the tank and placing this in the way, the micro bubbles will go all over the plants. The only thing you see is the CO2 line going into the tank.

    So simply attach the CO2 line to the spray bar to hide it.
    If you use a sump, use the overflow box to hide the line.

    The problem with filters, powerheads etc,(they burp and blech out large bubbles as well as smaller ones) is they do not produce the fine bubbles that a good diffuser will so you have less dispersal and contact time. Smaller bubbles means that you can more evenly distribute the bubbles and they are less affected by buoyancy.

    If they dissolve, you add more, but be careful, make sure the fish are okay. I have not killed a fish to date using CO2. I have killed shrimp:) But they taste so good.

    1.
    The real issue though is getting your current right.
    Most folks could use some improvement there.
    Hide the ugly stuff, make the flow pattern better through the plants etc.
    This will be the biggest user issue doing this.

    2.
    The other user issue, the distance the CO2 travels up before it hits the current.
    I placed the disc and the venturi right at the current input so that it is immediately blasting the pure CO2 all over.

    3. When paying around with CO2, be careful, it can kill fish and shrimps. If you monkey with it, make sure you are around during the time you adjust it. Do not wonder off, do not go to work after setting it in the morning. Wait till you have some time. Then watch. Be competent.
    Refer back to the mechanisms also in Fick's 1st law.

    Smaller tanks will have little trouble.
    Larger ones might consider the large flat stones above and better flow routines.

    Regards,
    Tom Barr
     
  15. Cornhusker

    Cornhusker Guru Class Expert

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    Re: CO2 issues? Read this

    :) tom, when i first started using co2 i tryed the defuser made by eheim. clogged very easily,but had very fine bubbles when working properly.i noticed that the stone you recomend requires at least 25 psi to work properly. i have a factory preset eheim regulator on my 75 gal tank ,do you or anyone know how much psi this regulator is set at?regards,cornhusker :) :)
     
  16. euripides6996

    euripides6996 Junior Poster

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    Re: CO2 issues? Read this

    Hey Tom et al.

    Some questions:
    - I'm assuming that the target concentration of CO2 remains around 30ppm whether you're misting or dissolving? ('misting' sounds like the SAM equivalent of 'huffing' or 'dusting'...)

    - Do the CO2 bubbles in misting contribute to the ppm?

    - Does it matter what kind of diffuser is used? There are the 'standard' cintered glass diffusers which come with some CO2 kits that would seem to achieve the same objective that you mention but have relatively low surface area.

    - Anyone know how you clean the diffusers? I have one with algea on it and I've no clue how to get it clean....

    - When you're using both a venturi reactor and a diffuser, are you using a manifold on the tank to split the CO2 supply, a standard airline gang-valve or something else entirely? I couldn't tell from the discussion whether the airline loop in the venturi was disconnected and the 'burb' hole was connected to a diffuser...

    - Does the misting only work if the leaves are large enough to 'catch' the bubble on their underside?

    Thanks...

    Will
     
  17. bonklers

    bonklers Junior Poster

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    Re: CO2 issues? Read this

    Tom, do you have any experience using the diffusers in your link (from Aquatic eco-systems)? I wonder how many bubbles/min you have to set your needle valve in to get that 25 psi.

    As allways, you keep surprising me with your ideas.

    There are just a couple of things though, CO2 diffuses much more easily than air does in water, so will the micro bubbles last long enough to dwandle around the tank? And will the bubble last longer if you cranck up the CO2 to 30 ppm first with efficient/external reactors and then go over to CO2 mist delivery?

    Is there any pictures to be found how this CO2 mists' looks like? I wonder how tiny the bubbles must be.

    Greets,
    Bonklers
     
  18. turbomkt

    turbomkt Lifetime Charter Member
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    Re: CO2 issues? Read this

    Bonklers,
    It's not the BPM that you've got to adjust but rather the regulator. That's what takes your 800 or so psi of CO2 down to 15-30psi (Everybody uses what works for them, right?). After that, you use the needle valve to adjust the flow rate.

    The flow rate should be a factor of supplied psi and backpressure from your method of CO2 diffusion.

    --Mike
     
  19. fishface

    fishface Guest

    Re: CO2 issues? Read this

    here's my experience after trying this method after only 2 days. i've got more thread and green spot algae than ever. but lots of bubbles... :confused: and thats the only thing in my regime i've changed.
     
  20. defdac

    defdac Lifetime Members
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    Re: CO2 issues? Read this

    Today is my first day with a wood-diffusor placed under a vertical spray-bar. A second powerhead is also making a strong current right under the surface, so the microbubbles travels to the other side of the aquarium withough reaching the surface and attaching under leaves.

    Does this look ok, or have I totally misunderstood the whole thing?
    [​IMG]
     
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