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Thread: Air Diffusers - Large or Small Bubble

  1. #1
    Oyagoi kntry's Avatar
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    Air Diffusers - Large or Small Bubble

    I'm ordering additional air diffusers for the mud pond. They come in standard and high capacity. The high capacity puts out more air but the bubbles are larger.

    Which would be better? I've always been told smaller bubbles but this one puts out less air.

  2. #2
    Meg
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    Oyagoi Meg's Avatar
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    it is all about surface area of the bubbles, not the amount of air, a million small bubbles have more surface area for air exchange than a couple big bubbles
    but if it is for more current in the mud pond I am scratching my head along with you??


    edit...
    found this quoat from Larry
    "(large air bubbles move lots of water with little foam production). Good foam fractionators make mediocre airlifts (small air bubbles move less water but mfg lots of foam)"
    I know it its about producing foam, but it also answers the production of current question.
    so
    smaller bubbles have more surface area to add oxyen to the water but bigger bubbles move more water.

    does that help you decide?

  3. #3
    Daihonmei PapaBear's Avatar
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    Since adding current to a mud pond is pretty much a non-issue the "big bubble/high volume" unit is a waste of energy with little benefit. Go with the fine bubbles but use extra air stones. That way you get high volume but better oxygenation.

  4. #4
    Oyagoi kntry's Avatar
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    Thanks, Meg and Larry.

    If I remember right, the last ones Greg ordered were the high capacity, larger bubble and he was very happy with them.

    I was planning on getting the smaller bubble but wanted to make sure I was getting the right one.

  5. #5
    Oyagoi
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    What are you using for an air pump?

    While there is no doubt that smaller bubbles mean greater direct oxygen transfer to water, in a mud pond, especially a large one (half acre plus) this effect is a tiny addition to the overall oxygen budget. Of much more import is the actual movement of water both across the surface and across the substrate (bottom). Water brought to the surface undergoes gas exchange very efficiently most of the time, this effect (water constantly flowing across the surface then across the bottom) is a much greater contributor to the oxygen budget in a mud pond. The water across the substrate is actually "filtered" (for lack of a better word) as it comes into contact with the sides and bottom. More contact, more filtration effect.

    Also, depending upon your water quality, small pores will stop up with calcium, sometimes in a few days or weeks. Larger ones take longer to stop up and need service.

    I've tried 'em all......I prefer bonded silica stones with large pores over rubber diffusers or leaky hose.

    For pumping air, I prefer a rocking piston pump (almost never breaks and needs very little service) over most others. Second is a carbon vane pump, third a diaphragm pump (both prone to breakage over time and require regular parts exchange as maintenance).

    Be sure the diffuser has a "plate" to sit on over the mud or it will dig one heckuva hole in the bottom.

    Brett
    Brett

  6. #6
    Tategoi
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    Sandy the smaller bubble will give you better water movement/lift. There is very little gas exchange between the bubble and the water and it's at the surface where the gas exchange takes place, so the more water being turned over at the surface the better.

  7. #7
    Oyagoi kntry's Avatar
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    Brett, thanks for the advice. That’s what I was looking for.

    I have a 6500 gph pump set up to pull water about 1’ off the bottom and spray it out across the surface of the pond through a 2” capped pipe. The cap has 10 pencil sized holes drilled in it. This is my preferred choice to move the water from the bottom to the surface as it not only moves the stagnant water to the top, it helps to cool things off. The problem with running it is the water gets so “thick” with stirred up red clay.

    The pond is approx. 30x65x3.5-4’ deep. It’s not completely filled yet. I was checking the water twice daily but now only about 1-2 times a week. It has settled down and seems to be stable. pH is stable morning and night at 7.7-7.8. I can’t seem to get the alkalinity or hardness above 40 though. It is going on 5 months old so it’s still new.

    I have a Hakko air pump that I was using with the diffusers but I “borrowed” the diffusers. I was also afraid of just what you’re talking about with them digging holes in the bottom. That would be a nightmare since the pond is all sand and we packed in 480 yds. of red clay to seal it.

    Thanks for the help, Graham. It’s great to hear from you. Where have you been hiding?
    The views expressed above are my own personal views and, as such, do not necessarily reflect the views of the AKCA or the KHA program.
    SANDY

  8. #8
    Daihonmei
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    go with what Brett stated....
    one issue not mentioned but deserves much more consideration is back pressure created by the two different difusers.
    typically small bubble difusers have much less air volume passing through them even when using the same air pumps so the small bubble versus large bubble is not an issue that can be discussed in a vacuum.
    Discussing small bubble versus large bubble as a stand alone topic continues to perpetuating the simpleton mindset pervasive within the hobby.

  9. #9
    Oyagoi kingkong's Avatar
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    I have no difusers, through them away. Open pipe, no clog, easier on blower esp. diaphram type.

  10. #10
    Oyagoi kntry's Avatar
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    Gary, I thought about doing that but would have the same issue with it digging holes in the bottom. The only way I can think to suspend the pvc in the pond is by tying bricks to the pipe to make it sink below the surface. When I pulled them out, the bricks were covered in red clay so I know they were sinking into the bottom clay.

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