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CO2 Fluctuations?

Discussion in 'Non-CO2 Methods' started by gabcas0319, Feb 8, 2017.

  1. gabcas0319

    gabcas0319 Junior Poster

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    Hello! some time ago when i was experimenting with CO2 my tanks gets a lot of BBA, then i change to a non co2 excel tank and many of the BBA die, now BBA dont grow but there some that still there and dont die! i was checking the co2 in my tank and in de morning when the lights are off the co2 is arround 5 or 6 ppm (ph 7,5-KH 5-6) but at night at the end of photoperiod the co2 changes to 1,5ppm (ph 8- kh 5-6) so i was wondering if this co2 Fluctuations is the cause? and if do i should up the ph of my tank to lower the co2? thanks!
     
  2. gnovince

    gnovince Junior Poster

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    Have you tried spot treating the BBA with excel with the filter off? I keep filter off for about 10 minutes so there isn't any flow and it usually kills off the BBA. It eventually turns red and dies off.
     
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  3. gabcas0319

    gabcas0319 Junior Poster

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    thanks i'm going to try!
     
  4. edelry.junior

    edelry.junior Plant Enthusiast
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    CO2 variation throughout the day is a normal thing, specially on a tank without CO2 injection. This should not cause any issues as far as you are not overlighting your tank. One important thing you should consider is that changing the pH with acids/chemicals will not add CO2 to your tank.


    First of all, the CO2 content as measured on the pH/KH table considers you have 100% pure water. You might have something on your water that throws that calculation off, some acids through your pH down, very high levels of phosphates might interfere with KH as well.


    So, how to measure it? One simple way would be checking it on degassed water (CO2 excess is removed, or "degassed"). Let water from your tank sit in a container for a couple days (or air it with an airpump/airstone for 30 minutes) and measure the pH/KH. Because of exchange with the CO2 present in atmospheric air (Henry's Law if you would like to google), the CO2 content will be around 3ppm, in usual situations (it would be a bit lower if you were to be in a high mountain, for example). If you inject CO2, you will get a 10x increase in CO2 for every 1 point drop in pH (e.g. 3pmm at 7, 30ppm at 6 and 300ppm at 5 pH).


    After checking you values (pH 7.5 and KH 5-6), one would say that with those values you have a maximal of 3ppm (given you do not inject CO2), and something in your water caused the pH to be a bit lower than "normal". Considering KH 5.5, your pH should be 7.8 (around 3ppm, which is the maximum the atmospheric air can provided) instead of 7.5, in this case a 0.3 pH "deviation" caused by something in your water.


    This would also mean that by the end of day you would have pH 8.3 (+ 0.3) and the CO2 concentration would be below 1ppm, just as expected on a non CO2 tank. That is what happens in many lakes as well. So don't worry about this variation, as this is perfectly fine, as long as the rest of the system is well balanced, with the right amount of light driving the system, and the right amount of biomass, fertilizers, etc.


    If you do not inject CO2, then just assume your highest level will be around 3ppm. Also, Seachem Excel (or similar products based on Glutaraldehyde) is adding photosynthetic intermediates, but not CO2 :)


    BBA is a nasty algae. If spot treating does not work, I would advise manual removal. But more importantly, do not aim at fighting the algae, go for the plant healthy growth. When plants grow well, algae does not. And that has also been well observed in many lakes, and also by many people in the hobby.


    Best luck Gabriel :)
     
    #4 edelry.junior, Feb 9, 2017
    Last edited by a moderator: Feb 9, 2017
  5. mexicatz

    mexicatz Junior Poster

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    Not op, but I've been letting my water degas in a bucket for 24 hours before water changes in an attempt to battle BBA caused by co2 fluctuations in my low tech tank. Is this a sufficient amount of time for co2 to be removed from the water?
     
  6. Christophe

    Christophe Subscriber
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    Got a powerhead to run in the bucket? Keep the surface turning over, that can help a bunch.
     
  7. Dale Hazey

    Dale Hazey Junior Poster

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    Do water change right before lights out might be another option besides aging the water.

    If aging it with a powerhead or pump or airstone, 6-8 hours should be long enough to degass excess nitrogen and co2.
     
  8. mexicatz

    mexicatz Junior Poster

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    No powerhead, I might try the water change before lights out method.
     
  9. VaughnH

    VaughnH Lifetime Charter Member
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    I have found it very interesting to make a change in how I use a drop checker (and I do know that Tom disagrees with me about the use of a drop checker) so I can see lower CO2 levels with more accuracy. Normally we use 4 dKH water, distilled water with enough bicarbonate of soda in it to get a 4 dKH carbonate hardness, in the drop checker, because that solution, with API pH reagent in it, will be green at about 30 ppm of CO2. I use much lower KH water. If you use 1 dKH water, for example, you can read CO2 levels around 10 ppm and less. Here is a chart showing the color vs ppm CO2 for various KH solutions in the drop checker:
    [​IMG]

    This lets you watch the CO2 level in the tank as it slowly changes throughout the day. Just keep in mind that a drop checker takes at least 2 hours to read correctly. If nothing else, doing this gives you a better appreciation of how even the CO2 that is naturally in the water changes during the day.
     
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