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Thread: struggling to find CO2 balance and water change clues?

  1. #1
    Join Date
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    Question struggling to find CO2 balance and water change clues?

    Hello everyone,

    I've been having a heck of a time finding the lighting and CO2 balance in my newest setup. I don't have much of algae problems to speak of, but growth is far from optimal in some plants, primarily those who are poor CO2 competitors, ie rotala macandra green, HC, pogostemon stellatus.

    Today I changed the water towards the end of the day and noticed that my ATI light was at 18% power (on its way to OFF) when I finished and I still saw a great deal of pearling...pearling I do not see when the lights are up to their scheduled power of 40%. I know plants pearl very well after a water change, but could this be a clue as to how low I can set my lighting and still get good growth, or is this just a "happy" response from the plants only due to a water change.

    I figured I would reduce the lighting further and will be able to back off the Co2, it has been stressing fish. Could I back off to say the 20% level I saw the pearling at after the water change provided I found a good CO2 level? The trimmed stems of the hygrophila pinnatifida were pearling very well at the 18%, the HC like I have not seen except with water changes.

    Please share your thoughts on this. Thanks!
    Last edited by ShadowMac; 03-25-2012 at 04:24 PM.

  2. #2
    Join Date
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    Smile Generally Safe for Inverts & Filters; Do Not Exceed 2-ppm

    Hi Shawn,

    Technically all pearling means is there is photosynthesis and O2 saturation.


    A couple of possibilities come to mind, beyond the obvious that the water change is introducing a good amount of oxygen.

    1. The plants with current CO2 could use more light.
      1. Conversely, you could reduce CO2.

    2. Well into the photoperiod, 3 or 4-days after a water change add 1-ml of 3% Hydrogen peroxide per 5-gallon of water (do not do this if you are medicating the tank).
      1. If the plants begin to pearl, try it again 4-hours later (or the next day) with half the amount (0.5-ml/5-gal).
        1. If they pearl, 4-hours later (or the next day), try half as much again (0.25-ml/5-gal).
        2. If they do not pearl, 4-hours later (or the next day), add half again as much (0.75-ml/5-gal).
        3. At this point, the arithmetic is fairly simple, of course it can be taken any number of steps further, but… there really is not much to be gained.

      2. If the plants do not pearl go to step 3.

    3. You have high dissolved organic material.
      1. Test for that with PP (do not do this if you are medicating the tank) (this might cure what ails you, as well).
        1. 0.03-grams of KMnO4 for each 5-gallon of water reapplying as necessary until the water remains at least a faint pink for four-hours. Adding aeration is a good idea during test/treatment.
        2. If it required more than 0.1-g PP/5-gal then DOC is a definite problem.


    My PP recipe:
    I like 1% solutions since each milliliter of solution is 0.01-grams (10-mg) KMnO4.

    • 10-grams KMnO4 into 990-mililiters of distilled water.
      • In real life, I mix 10-g into 900-ml and “top-off” to 1-L.
      • Weighing is the most accurate way to measure water, but close is good enough.

    • Diluting 1-ml of the 1% solution with 9-ml of distilled water yields a solution that each milliliter is 0.001-grams (1-mg) KMnO4.
    • If you do not trust my calculations, Tug found a wonderful site run by the “Koi and Water Garden Society of Central New York” that has a PP Calculator.
    • To keep the numbers even I used 1.6-ppm, though up to 2-ppm is good.
    • If you think you have a parasite problem 2.0-ppm is a good number for the tank.

    Biollante
    The first sign we don't know what we are doing is an obsession with numbers. - Johann Wolfgang von Goethe

    Disclaimer: I am not trying to make you mad, it is just what I am, an evil plant monster, 'nuf said.

    • I believe the information I am giving is sound, I am not a veterinarian, professional chemist or particularly bright and certainly not a "Guru.".
    • I assume you are of legal age, competent and it is legal for you to acquire, possess and use any materials or perform any action in your in your jurisdiction.
    • When in doubt "don't."

  3. #3
    Join Date
    Mar 2010
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    Thanks Bio.

    would the fact I saw photosynthesis occurring give a clue at the light level I need to get growth? I don't have a PAR meter and this ATI light packs quite a punch. Since I want to minimize CO2 stress, I need to minimize the light without going too low. I've tried ranges from 30%-60%, if I turn the light up I will get pearling, so I don't think the system is O2 stressed..all it takes is more light. But I don't want to overdo the lighting. Now i'm wondering if i've been undershooting it. Pearling is noticeable at 40-50% and of course increases with greater intensity.
    Last edited by ShadowMac; 03-25-2012 at 04:33 PM.

  4. #4
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    Smile Quantitative vs. Qualitative

    Hi Shawn,

    Yes I believe what you saw indicates low light, if what you are looking for is optimum growth. There is nothing inherently wrong with plants growing without pearling. As this seems to be a concern of yours (and many others) I simply offer a way to “know.”


    You may well be correct, the system isn’t O2 stressed. In this case, O2 stress isn’t really the issue, though on the flip-side it could be a symptom. Given the other things, you have mentioned there is a lot to be said for knowing.


    The above method is simply the quantitative analogy to the qualitative method you are employing, without spending a ton of money on various electronic devices.

    The above method may also add to your confidence in your quantitative analysis.


    Biollante
    The first sign we don't know what we are doing is an obsession with numbers. - Johann Wolfgang von Goethe

    Disclaimer: I am not trying to make you mad, it is just what I am, an evil plant monster, 'nuf said.

    • I believe the information I am giving is sound, I am not a veterinarian, professional chemist or particularly bright and certainly not a "Guru.".
    • I assume you are of legal age, competent and it is legal for you to acquire, possess and use any materials or perform any action in your in your jurisdiction.
    • When in doubt "don't."

  5. #5
    I've done several WC's at night (8-9pm) in recent weeks Biollante and noticed the plants pearling away like mad as if the lights were on. I could only guess as to what that all means, so I won't...

  6. #6
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    Smile Just In Case This Was A Serious Reply, I Will Answer It As Such

    Hi,

    No need to guess,
    it means by use of large water changes you are maintaining highly oxygenated water and removing wastes from the system and there is enough light for photosynthesis to take place. I have many aquariums and containers that are ambient lighting only that pearl on big water changes. Some pearl anyway.

    • If they are “pearling” in low/no-light then
    • it is not “pearling” in the sense we misuse the word,
    • it is simply un-dissolved air (bubbles) trapped vigorous by mixing.


    Large water changes are an effective method of dealing with water quality. Not unlike the way rivers and spring fed lakes operate.


    Biollante
    Last edited by Biollante; 03-25-2012 at 09:53 PM. Reason: by 2nd air not oxygen
    The first sign we don't know what we are doing is an obsession with numbers. - Johann Wolfgang von Goethe

    Disclaimer: I am not trying to make you mad, it is just what I am, an evil plant monster, 'nuf said.

    • I believe the information I am giving is sound, I am not a veterinarian, professional chemist or particularly bright and certainly not a "Guru.".
    • I assume you are of legal age, competent and it is legal for you to acquire, possess and use any materials or perform any action in your in your jurisdiction.
    • When in doubt "don't."

  7. #7
    Join Date
    Mar 2010
    Location
    Grand Forks, ND
    Posts
    970

    trying to find the happy place

    those tests seem worthwhile and will provide me with more information to make a an informed approach to getting the best growth. The HC hasn't been carpeting well and some issues are noticed from time to time, but nothing I can really put a finger on. I have decreased surface agitation as it was considerable in previous weeks and reduced CO2 this weekend to compensate for less surface agitation. Today I'm observing improved fish behavior and better signs of growth, ie pearling. Come on Bio, it is pretty when it pearls

    Since I have decreased surface agitation I will be aerating at night to enhance gas exchange.

    I would like to know for sure, so I will complete those suggested tests to see what happens.

  8. #8
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    Mar 2010
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    I made sure it was not trapped air...I witnessed the gas leaving the cut ends of a stem of hygrophila pinnatifida as well as damaged portions of HC. It was without a doubt "pearling"

  9. #9
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    Smile Too each their own.

    Hi,

    I do not know if Squidly’s comment was serious or a sad attempt at a “gotcha.”

    • A couple of years ago I offended a bunch of people over “pearling.”

    For most, it really doesn’t matter that we understand how things work, just that they do. I push buttons on my phone and I talk to whoever is on the other end…


    Pearling isn’t that big of a deal to me, I guess a little light pearling is nice.

    In some cases, the pearling makes it look “sweaty.”

    I also am aware that folks photographing their tank often like to do that the day after a large water change.

    I am also aware some cheat, amazing what a shot of Hydrogen peroxide or a dose of Sodium percarbonate can accomplish.



    Biollante
    The first sign we don't know what we are doing is an obsession with numbers. - Johann Wolfgang von Goethe

    Disclaimer: I am not trying to make you mad, it is just what I am, an evil plant monster, 'nuf said.

    • I believe the information I am giving is sound, I am not a veterinarian, professional chemist or particularly bright and certainly not a "Guru.".
    • I assume you are of legal age, competent and it is legal for you to acquire, possess and use any materials or perform any action in your in your jurisdiction.
    • When in doubt "don't."

  10. #10
    Join Date
    Mar 2010
    Location
    Grand Forks, ND
    Posts
    970

    Poor Mr. Beedle...beatle..

    i didn't consider that squidly's response may have been sarcasm...

    oh well...

    I guess my conundrum has been what light level is enough to get growth and are there clues I can go by without buying a PAR meter, which essentially is what you have provided above in your first post. Today the tank looked good, but one day doesn't translate to much. A week or two will tell the truth of it.

    Thanks for your help as always, Biollante.

    Cheat with photos!? :O never! who would do that?!

    I often forget that most of the photos we see are poor representations of what is to be reasonably expected. For the most part, i compare growth in my tanks to each other especially when they contain the same plants. For example, the HC in my 12 gallon is doing superbly while the HC in the 48 is doing poorly. S. repens in 7.5 gallon and 12 gallon doing great...48, poorly. So something is going on with the 48 that isn't with the others. Flow is ample, i have a large filter and an MP10...that leaves CO2 and light. I had hoped that the water change pearling was evidence I could reduce lighting substantially and focus primarily on CO2 for a similar result. However, no matter how much I try without a water change that kind of metabolic activity doesn't occur in my plants until the light gets around 40% power.
    Last edited by ShadowMac; 03-26-2012 at 12:38 AM.

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