Redfield What?

Discussion in 'Additives' started by potatocouch, Mar 24, 2016.

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  1. potatocouch

    potatocouch Member

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    Stemming from @macca_75 Redfield Ratio out of whack ...

    I heard of it but don't really understand it ...

    So this is Redfield ratio:
    ai.imgur.com_Lq2diVE.jpg

    Are we aiming for the yellow cells there?

    So for mixed reef tank, my understanding SPS is intolerant of No3 and preferably maintained at rate < 5 ppm ...
    if that's the case, is it correct to say that we should be aiming for these balance:
    • No3 2.5 ppm & Po4 0.3 ppm.
    • No3 2.5 ppm & Po4 0.2 ppm.
    • No3 1 ppm & Po4 0.1 ppm.
    • or probably No3 5 ppm & Po4 0.5 ppm
    ?
  2. Franklin Dattein

    Franklin Dattein Member

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    106:16:1 is the consumption ratio and there is no need to aim for a balance.

    Bacteria will consume 1 part of phosphate, for every 106 parts of carbon and 16 parts of Nitrate.

    Balance isn't important for the aquarium. What is important is that there is enough of the 3 elements, to enable bacteria to keep consuming the other elements, specially if you are using carbon dosing as a method of reducing N and P.

    That is why organic carbon is an effective way to reduce nitrate, because when C is added, it enables more consumption of N and P.

    So, it isn't really about keeping the balance, it is much more about understanding the balance, so it gives you some predicability.

    For example, if one starts carbon dosing in a tank with 16N and 2P, the Redfield Ratio is helpful to predict that N will be depleted, when P reaches 1 parts. Therefore, leaving another 1 part of P in the water, that bacteria won't consume.
    Also, adding more C to this tank won't work, because the ration is broken by the lack of N.

    If the goal is 0N and 0P, then the person needs to find another method to reducing the remaining 1P.
    The most common solution would be GFO or AO to remove the remaining 1P.
    Another alternative, is to dose more N. In this case, the ratio will tell 16N have to be added to deplete that remaining 1P.

    I hope I din't make it even more confusing :p
    Last edited: Mar 24, 2016
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  3. chimaera

    chimaera enjoy the little things

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    Nice summary!
  4. macca_75

    macca_75 Member

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    that's pretty much it but if it's "out of balance" you also run the risk of growing other "unsightly" bacteria forms, which is why we aim to actually keep them in balance (so they can be reduced at an even rate as explained).

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