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  • CO2 Fluctuations?

    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!
    Gabriel Castro.

  • #2
    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
      Originally posted by gnovince View Post
      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.
      thanks i'm going to try!
      Gabriel Castro.

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      • #4
        Originally posted by gabcas0319 View Post
        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!
        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
        Last edited by edelry.junior; 02-09-2017, 10:58 AM.

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