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Thread: Foam

  1. #1


    Hi all

    I'm starting to get a little bit of foam on the surface. What causes this?

    My water test readings are stable for over a month at
    Ammonia - 0
    PH - 7.2
    KH - 100
    GH - 250
    Nitrite - 0
    Nitrate - 50

    Pond is 750 gallons
    6000l/hr pump to a oase 6000 pressure filter
    2500l/hr pump to another similar sized foam filter
    + 5 x anoxic baskets and plants

    Any ideas

  2. #2
    I regularly get asked to explain how these bubbles form and how to avoid the situation so, to save retyping, here is a copy of the answer I usually give:

    If foam in a pond isnít due to an overnight spawning, then it is most likely caused by dissolved organic carbon (DOC) and it primarily comes from undigested food or partly digested food (mainly protein) in fish excrement. Carp are genetically predisposed to eat whatever they find whenever they find it. In the wild, carp don't normally find as much protein at any one time as we feed them when we feed large amounts of high protein food a few times a day, especially when we want to encourage growth. Wheat germ can also be a problem since it often contains protein that is a low digestibility form and therefore is best fed in small amounts at any one time to prevent there being too much for the gut to deal with as it passes through.

    Food passes through the gut at a steady rate and there are only a limited amount of enzymes available for catabolism (breaking down the food as the first part of the digestive process). If only small amounts of food are eaten at a time then there will be sufficient catabolic enzymes for it to be fully digested. If we feed too much high protein or low digestibility protein at any one time, there wonít be enough of these enzymes to break it all down in the limited amount of time that the food is in the gut. The result is that the food won't be fully digested and will emerge at the other end as DOC.

    You can remove DOC by protein skimmers and/or water changes but koi food is expensive so, if a percentage is excreted undigested, it is just wasting money.

    My suggestion is that the feeding regime is the first thing that should be addressed either by feeding less food or the same total daily amount but in smaller portions spaced throughout the day. This should dramatically reduce the DOC and allow the normal DOC reducing bugs to be able to cope with DOC from pheromones and other metabolic wastes that aren't so easy to eliminate.

  3. Thanks Keveke, Frimley Koi keeper, crazyreefer, Goonerharwood Thanked / Liked this Post


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