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CO2 meter on low tech?

Discussion in 'General Plant Topics' started by baron von bubba, Oct 26, 2009.

  1. baron von bubba

    baron von bubba Junior Poster

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    has anybody done tests with a co2 meter on a low tech?

    i mean to see how much extra co2 a well stocked gets from fish?

    i struggle to believe the ppl who say to have no surface agitation to keep in all of the extra co2 fish/bacteria produce, as i cant see that it would actually amount to any significant amount.

    thanx
     
  2. Philosophos

    Philosophos Lifetime Charter Member
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    CO2 meters cost a fair bit, but a drop checker doesn't have to. I'm betting a low KH solution might reveal a bit about a tank. Try reducing surface disturbance for a few days, then run an airstone after. You could keep the variables in decent check doing one after the next in the same tank.

    I've got my own conclusions based on indirect calculations of respiration and approximating degassing rates, but a more direct test would be far more telling.

    -Philosophos
     
  3. baron von bubba

    baron von bubba Junior Poster

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    thanks
    i haven't set the tank up as yet, but i like to get things straight in my head first! :0)

    explain a low KH solution please.
    i know ppl use 4KH solution with ph test solution in DC's
    but i always just buy the ready mixed so i'm not too up on the above method.
     
  4. Philosophos

    Philosophos Lifetime Charter Member
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    Just take some of your 4kh solution and use it in perhaps a 1:7 or 1:3 solution with DI H2O. 1:7 would be .5kH, 1:3 would be 1KH.

    Depending on how things go I might be able to run the experiment at the same time as you. I'll know by tomorrow.

    I doubt this will be anything conclusive in terms of fine details, especially given the difficulty of controls. Still, if it's highly reproducible and yields definite results, then it'll be a great way to settle the issue. Tons of people have drop checkers and 4KH solution that they can dilute.

    -Philosophos
     
  5. Philosophos

    Philosophos Lifetime Charter Member
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    I'll be starting this little experiment tommorow for the air pump test. I wouldn't mind if everyone gave a read over and added any aother variables they think would be relevant to the test. Unfortunately an accurate pH test of the column is out of the question right now as the electrode in my meter drifts horribly.

    The tank is a standard 10 gal with one pair of ~4 inch long albino bristlenose and a plant density that should be decent enough to represent the average tank. Filtration will be a Whisper 10 power filter (90gph) without media, and a Stellar 20 air pump running 2.2gph at 2.9psi.

    The drop checker is a generic one from Aquatic Magic. I will be adding aproximately 2-3ml of .5 KH (8.93ppm) solution to it achieved using sodium bicarbonate, along side about 2 drops of low range pH indicator containing bromothymol blue. the drop checker will be placed in the front left corner, farthest away from the airstone in the back left. I hope to make observatons every hour or two.

    As for the test without the air pump, I'm a little more unsure ofhow to do this. I can't spend an entire week at home taking hourly measurements. I could take measurements at the same time of day towards the end of the light cycle.

    I understand that a drop checker isn't going to give me the most accurate reading in the world, but I do hope that the saturation difference will be by enough to offer a very distinct difference in color. Hopefully one that will be noticable if I take pictures.

    -Philosophos
     
  6. shoggoth43

    shoggoth43 Lifetime Charter Member
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    The only variables I can think of would be temperature ( presumably controlled ) since that would affect all sorts of metabolisms. You would also need to make sure you don't have any sort of surface film which would affect your gas exchange ( also presumably non existant ).

    -
    S


     
  7. Philosophos

    Philosophos Lifetime Charter Member
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    Temperature would be a good one.

    How do the "don't disturb the surface" type react to surface film? I'd almost think it desirable.

    -Philosophos
     
  8. shoggoth43

    shoggoth43 Lifetime Charter Member
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    I have no idea. I know that if there's a film and my discus are breathing a little hard removing the film alleviates that. Whether that's a gas exchange issue or maybe a getting rid of crud in the water that's decomposing and letting the filter "catch up" I don't know. I'm inclined to go with gas exchange not letting in the O2. I'm not sure how I'd test and I'm more inclined to just clear the film off and not worry about it, but I can see how it might be a heavy influence.

    -
    S
     
  9. aquabillpers

    aquabillpers Lifetime Charter Member
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  10. Tom Barr

    Tom Barr Founder
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    I spoke with her about this topic and my general thoughts on stability and adaptation for plants and CO2.

    I have grave doubts about the measurements in absolute terms, there's relative terms like a specific movement in pH, or relative to some known amount, but if you do not really know what those known amounts are, then measurement in ppm's is not really going to tell you stability.

    Measuring over time and data logging is critical to looking at these issues, CO2 demand, light intensity, plant type/species make large differences also.

    Filters, movement of water etc, anything to do with O2 use/production/transfer becomes even more important in a non CO2 enriched aquarium.

    This is one way to measure CO2:

    http://www.omega.com/manuals/manualpdf/M0783.pdf

    Another is this method:

    Determination of Carbon Dioxide in Water - Industrial & Engineering Chemistry Analytical Edition (ACS Publications)

    And yet the other is using the light based method from Tuft's that is used for YSI and the Oxyguard.

    We could also use something like a pH meter with a reference cell and KH but these need changed often. I'm not happy with any of these methods personally.
    They all have big trade offs. I think if you reads through these, you will see some large sources of error potential.

    If I remember right, the theoretical equilibrium value of CO2 in water at a specific temperature, sea level(pressure) and 350 ppm(concentration) in the air is 0.498 mg/l. This varies with the three conditions, so our results may vary.

    Still, distilled water and low elevation should be much less than 3ppm.
    I think folks will want to start there.

    I have to question whether these methods are correct particularly at lower values.

    Regards,
    Tom Barr
     
  11. Tom Barr

    Tom Barr Founder
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    I am looking at this method to get precise measure of CO2 in aquariums and samples at the microscale from various locations around the aquarium plant.

    Measurement of CO2 Dissolved in Aqueous Solutions Using a Modified Infrared Gas Analyzer System

    As you can see, this is far far more , accutate, reactive and responsive.
    Bit more involved also:cool:

    But using an IR and allowing a sample to degas from a carrier N2 gas, would allow very accurate measurement of the sample.

    IR's are not cheap, but not that bad either for research.

    If I could get a smaller IR that was good, then do a sample of water like this:

    Qubit Systems: LOW RANGE RESPIRATION PACKAGE (WITH FLOW METER)

    But water taken from the aquarium via a syringe, and allowed to equilibrate, then I could get very accurate measurements and no worry about any loss or time factors since the chamber would be sealed.

    You could even have multiple chambers pulled from the tank/same spot over 30 minute time frames etc and then measure with the IR later(not that one that's shown there).

    This is involved, but it's accurate and not cheap.

    I do not think you will get good resolution with cheaper methods or accuracy.
    There's just no calibration of reference standards other than eq with air.
    I've not found any test kit/pH meter that gave accurate readings there to date.

    Regards,
    Tom Barr
     
  12. Philosophos

    Philosophos Lifetime Charter Member
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    I'll just let the tank play out as it will then. This is an experiment I hope to seen prove through repetition with others rather than finite variable control.

    I would've started the first phase, but things came up today; posts, plumbing issues, vomiting. I Will start tommorow if I have time/feel better.

    -Philosophos
     
  13. Philosophos

    Philosophos Lifetime Charter Member
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    I'm not quite sure how I managed to make a post that short in reply to everything that's been said. I must've missed a couple of posts.

    The IR method is neat, Tom. I think I saw you post on it back when you and Vaughn were working on the CO2 meter with osmosis membrane and KH solution. Looks like it'd cost a small fortune to operate though; chromatography membranes aren't cheap.

    Anyhow, I'm hoping to get answers in this case that will not work on precisely calibrated numbers. The color of one drop checker with the same indicator solution, in the same tank will show if there is a significant difference within this tank between having the air stone there and not. The concept here is not about getting precise numbers; I simply don't have the means to do that right now. If someone donates some equipment to me then we'll talk :p

    What I do have is the means to show that under almost the exact same circumstances with the presence/omission of an air stone, more/less CO2 was present. I want others to be able to do the same who ask themselves the question of whether or to use surface disturbance or not. It's a simple experiment that can be done for less than $20 of materials, and most of us have those materials sitting around.

    Right now my drop checker with air stone in is actually not sitting far off reality; about 2.33-3.76ppm CO2 would be the actual number it correlates with. It's been holding steady during the hours that the light is on since yesterday.

    If there's no noticable differene when I turn the air stone off and let things sit with a HOB for a few days, then I'll call it a day. If I get a nice blue or bright yellow drop checker, then I've come closer to answering a question within the hobby. Maybe someone else will build on it, or I'll eventually have the resources to do a better test.

    -Philosophos
     
  14. Tom Barr

    Tom Barr Founder
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    Never put off taking care of a tank for time posting;)
    Never worth that. If you feel bad and not like working on the tank, need a break etc, okay.

    Yes, the damn CO2 thing is full of crappy trade offs.
    I am interested in an academic sense however.

    So the cost and various methods are less of a deterrent when it's considered vai that way.

    I'd like to compare the IR method to the Oxyguard meter. It's calibrated etc, but I want to check it against other methods that also critically calibrated and checked.

    I'm inherently suspicious.

    I have the data, some of it is explainable, but there are unanswered questions still in my own mind.

    Comparative review is the best approach rather than one sampling or one method, when we have broad based agreement from many methods, replications, applications, different people, then.........I can feel a bit better.

    Perhaps some see it as anal, I see it more as a "honesty test". How honest and sure do you want to be? But........the chance of being wrong is much less than just using one method and then comparing the various methods against one another with known standards.

    When we are talking about a non CO2 method, the differences are much smaller.
    Think about this:

    If you have 10X reduced rates of growth vs say 30ppm of CO2, how is this going to affect CO2 demand and other nutrient uptake rates?

    It's going to be much reduced as well.
    Like measuring NO3 in a high light CO2 enriched aquarium, the rate will be much higher and the resolution and the accuracy requirement is MUCH less.


    This is the problem in predicting/measuring uptake rates in a non CO2, things go really slow, and other sources and inputs of CO2/O2, nutrients can come from many other sources than when things are driven at the higher/highest rates of growth under high light/CO2 gas/KNO3 dosing etc.

    The bar is rather high to be sure of things, and the resolution and accuracy demands goes up when things are slowed down.

    Everything takes longer and plants can allocate very differently when they have their own sweet time.

    Regards,
    Tom Barr
     
  15. Philosophos

    Philosophos Lifetime Charter Member
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    The posts didn't take that long. Most of it had to do with the puking actually :p

    Might explain some of my hairbrained/half-assed post as well.

    I've never known science to work any other way. If the theory is sound, there should be multiple ways to test the concept. Unfortunately this hobby is light on the science end quite frequently; most of us don't seem to know why what we do works on some of the most essential levels.

    So the system compensates for its self in a way by taking up more CO2 as it's offered. At the same time (from what I've read) plants manufacture less rubisco in higher CO2 conditions. This would mean plants take up far more of the CO2 preportionately in low CO2 environments?

    -Philosophos
     
  16. Tom Barr

    Tom Barr Founder
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    And this is the biggest issue/factor within the planted hobby presently.
    Other aquatic hobby areas such as reefs, pathology, breeding/aquaculture are far more ahead on this topic.

    I honestly do not know.
    I know how I could answer this question, but would require enriched C13 labeled CO2 stable isotopes. I could then follow each CO2 molecule and see what % the plant incorporated into it's tissue regardless of CO2 enrichment at say 30ppm [0.7mM] or ambient air[0.05mM]. The % of CO2 could be tracked into the plant and the rest really matters not.

    Most of the CO2 in enriched systems is wasted to the air above. In non CO2 planted tanks, this is much different as it ebs and flows daily. Rates of degassing and uptake seems to be more constant at non limiting levels if I where to guess.

    when you have systems where you have many sources of CO2, how much is really debatable since it's removed as fast as it's produced.

    The same argument applies, perhaps weaker, with NH4 production from fish waste. It's taken up faster than the ability of our test kits to measure it.

    Again, we could use labeled N15 fish protein and see how much the fish gets of that N and then what fraction is cycled into the plant tissue.

    Still, stable isotopes are not that hard to do once enriched, but getting the enriched stable isotopes to work with to start ............is very difficult.

    The enriched material is where the cost is and then disposal. The measurement is not too bad cost wise.

    Tracking who gets what and the rates of production, transformation of various nutrients becomes much more difficult as things slow down. The differences become a lot more subtle and harder to tease apart.

    That is why I took another apporach for non CO2, I started with high light, CO2 enrichment, high non limiting ferts, then scaled what I knew there, down to the non CO2 growth rate.

    I know the rate of growth difference between those two basic methods, so I could predict fairly well the difference in uptake and growth.

    10-20X less. So 30ppm of CO2 would not be 1-3ppm of CO2 during the light period averaged etc.........

    Where ypou start at trying to get a handle on it also makes a big difference.
    It would be much harder to determine the rates of uptake for all 10 or so nutrient,s and light etc on a non CO2 tank over a few weeks, then you'd also have test and measure the soil as well.

    PITA. And one I chose to avoid.

    Regards,
    Tom Barr
     
  17. Philosophos

    Philosophos Lifetime Charter Member
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    Sounds like you'd have to obliterate an entire tanks contents; dry it, crush it send it through flash chromatography, etc. Definitely more difficult and costly than anything anyone cares to invest into this hobby right now. Perhaps large companies would, but I don’t imagine they’d give us the benefit of that information. They’d just charge us for it in their products.

    Still, it’s good to know how you’d go about it. I’m always curious as to the methods people like you use to figure out how tanks work.

    As an update to my little experiment, things were running around the 6.6-6.8 mark in the drop checker. I’d estimate somewhere around 2.8-3.4ppm CO2 based on the color. Unfortunately Mrs. Philosophos decided to re-introduce a fish from the quarantine, add another, and use tank water to adapt. Results for today are scrapped.

    I’m not sure when I’m going to get an entire day to monitor things again. I’ll probably just create a new thread for the whole works once I’ve got my results.
     
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