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  1. #1
    Member Hotrodmike's Avatar
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    O2 and temp go hand in hand

    Even thought it's not AP it does pertain to fish and the lack of O2 in warmer water .
    This was on the front page of this am's paper . Seems the lake has gotten so hot this summer the fish are going deeper and deeper to stay cool . The problem with this is lack of o2 at depth . Now the shore line is littered in dead fish
    http://www.statesman.com/news/local/...re-888467.html
    So I guess this should remind us all to keep a good O2 level as the water temps go up .
    Have A Kind Day
    Mike

  2. #2
    Moderator badflash's Avatar
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    Re: O2 and temp go hand in hand

    Bubbles are good. Set up your AP return to splash into the water. Easy aeration. An airstone with a battery backup works wonders.
    The best fertilizer is the farmer's shadow

  3. #3
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    Re: O2 and temp go hand in hand

    This is really important. Warm water holds less o2, and fish metabolism increases as temps go up, and therefore they use more oxygen, and emit more CO2, so good aeration is a must as temps increase. A power failure can be a disaster. Something to remember though is that most gas exchange happens at the surface. A deep fish tank is harder to keep dissolved oxygen up to appropriate levels than a shallower tank. This is because a deeper tank usually has less square footage of surface area relative to its actual cubic foot capacity. For instance a 4x4x4 tank has a higher surface to cubic foot ratio than a 4x4 by 6 foot deep tank. so the deeper the tank, the more aeration that you need to compensate for this ratio. When you see a stream of bubbles from an airstone, very little gas exchange takes place beneath the surface from the bubbles themselves. Most of the gas exchange comes from the upwelling current making surface contact caused by the bubbles rising. Think air lift pump. So basically the more current the higher the DO. You can accomplish this with airstones, larger pumps, and in a pinch, even a fan blowing across the surface of the water. Airstones with very fine bubbles can add better subsurface gas exchange than larger bubbles. Some of the membrane diffusers offer better aeration in this way.
    One thing that is often overlooked is the importance of CO2 removal. Water that is saturated with CO2 from fish respiration can hold less O2. So the more current the less CO2, and the higher the DO= happier fish.
    Lastly, when designing tanks, gallonage is often less important than footprint for this same reason. You can keep nearly the same number of fish in a slightly shallower tank with the same footprint as a deeper tank with higher gallonage. Obviously do not go to extremes.

  4. #4
    Moderator badflash's Avatar
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    Re: O2 and temp go hand in hand

    I agree with most of what you say, but not about adding O2 at the surface. Removal of Co2 is not as important as fish do not respond to it in the same way as mamals. Lots of studies show that the amount of O2 absorbed by the water is a function of pressure. The higher the pressure, the more oxygen is absorbed. This means that a stone deep down is more effective than one near the surface.

    My mentor designed and built recirculating systems powered by air lift pumps for intensive tilapia growth. He dug tubes 50' down for the air lift system and injected the air at the bottom. The water as it came out of the lift tubes was oxygen saturated and these tubes provide all the motive power for the raceway and biofilters.
    The best fertilizer is the farmer's shadow

  5. #5
    Moderator davidstcldfl's Avatar
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    Re: O2 and temp go hand in hand

    Wow Badflash, that would be neat to see the set up you were describing, with those deep tubes.
    What kind of a compressor was he using to pump to 50 feet deep ?...any idea of the air 'volume' he was using ?

    Would this help add extra oxygen Badflash ?.....
    If you could pump air, into the water return line, just 'after' the pump. The water is under some pressure there....or is this different then the 'pressure' at deeper water depths ?
    Maybe it would be so small of a difference, it wouldn't be worth it ?
    'Maybe' more so, if the return water was being sent towards the bottom of the tank(s) ?

    Here's a link to an interesting article written by Bob Heideman of Aquatic-Eco.
    He does mention oxygen levels in different water tempts...
    It also, talks about some of the different methods on adding oxygen...and which ones give the most oxygen for the energy being used.

    http://web.archive.org/web/200508280627 ... aerate.htm
    "Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same." - President Ronald Reagan

  6. #6
    Moderator badflash's Avatar
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    Re: O2 and temp go hand in hand

    He was using an O2 generator and it put out a lot of pressure. Typicaly a pump for AP doesn't put out a lot of pressure, maybe on 5'-10', but the more pressure, the more disolves. I'll find some pictures of the raceway and post them.
    The best fertilizer is the farmer's shadow

  7. #7
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    Re: O2 and temp go hand in hand

    Awesome, I am really interested in seeing the photos as well Badflash, sounds like a lot of work, and design ideas went into building this setup. Were the 50 foot deep airlifts pulling up ground water? That would be a great way to aerate well water, as it is usually devoid of O2.

  8. #8
    Moderator badflash's Avatar
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    Re: O2 and temp go hand in hand

    In the raceway system it was just circulating water. I have a SRAC publication on using it to move water through fish containments in ponds.
    The best fertilizer is the farmer's shadow

  9. #9
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    Re: O2 and temp go hand in hand

    if you have a submersible pump you can install a pvc "T" at the outlet and run a tube from above the surface to the verticle portion of the "T" turn on the pump and the discharge water with draw air from the surface and discharge air with the water. aquarium power heads used this method to force additional O2 into the water.

  10. #10
    Moderator urbanfarmer's Avatar
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    Re: O2 and temp go hand in hand

    Quote Originally Posted by rfeiller
    if you have a submersible pump you can install a pvc "T" at the outlet and run a tube from above the surface to the verticle portion of the "T" turn on the pump and the discharge water with draw air from the surface and discharge air with the water. aquarium power heads used this method to force additional O2 into the water.
    It's called the Venturi effect. Here is a link http://en.wikipedia.org/wiki/Venturi_effect or http://www.unu.edu/unupress/unupbook...e/80A01E08.htm

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