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Need a little help*understanding plants photosynthesis

Discussion in 'CO2 Enrichment' started by Co2, Jun 7, 2011.

  1. Co2

    Co2 Junior Poster

    Aug 20, 2010
    Likes Received:
    As I have a heavily planted and heavily fish loaded tank I'm alway juggling to get my co2 level as high as the fish can take while the lights are on. And then at night I give them 5 hours of air pump. As vie notice this seems to make them happy.

    My light comes on at 11:30am and the co2 2 hours before that at 9:30am. The light is off at 7:30pm and co2 and hour earlier. The air pump does not come on til 12am and off again at 5am.

    I understand at a very basic level that plants photosynthesis by using sunlight to turn carbon dioxide and water into food.

    The reason for the post is that I've noticed that an hour after the lights off, some of the fish are coming to the surface a few at the beginning but then more and more. I know it's O2 starvation but it's strange the co2 has been off for the past 2 hours at thus point.

    All I've been doing is putting the air pump on for an hour and all is well again.

    I just would like to understand what's really going on. How long does it take co2 levels to lower? Why there is no problem in the day only after lights out? When do plants start to release O2 from lights out?

    Should I really be on a 10 hour light period?
  2. nipat

    nipat Guru Class Expert

    May 23, 2009
    Likes Received:
    I think it would be better to start air pump immediately after light-off.

    CO2 can linger long in the tank. With my new and taller than before tank,
    drop checker would still be green even hours after turning off CO2 if surface
    agitation was not enough. And even though I had increased agitation, the tank
    seemed to lack O2 somewhat that the critters were OK but organic matters
    didn't degrade well (leading to BGA even with OK level of NO3).

    At first I couldn't find where to place an airstone without creating splash.
    Then I got the idea of putting it into the surface extractor.
    And that improves things.
  3. Crispino Ramos

    Crispino Ramos Guru Class Expert

    Apr 23, 2010
    Likes Received:
    Increase water circulation in the tank, you can use a power head.
  4. Biollante

    Biollante Lifetime Charter Member
    Lifetime Member

    Jun 21, 2009
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    We All Like To Breathe 24/7/365


    Remember that plant respiration goes on 24 hours a day. :gw

    You said you have a “heavily planted tank,” remember that as photosynthesis ends the plants go from net producers of oxygen to net consumers’ oxygen.;)

    A little surface agitation and increased circulation, whether by air pump, powerhead, redirecting water flow toward the surface will go a long way toward keeping flora and fauna happy.:cool:


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