Water Surface Milky/oily layer

Discussion in 'Beginner Discussions' started by RaveMan, 26 May 2008.

  1. RaveMan


    Posts: 54
    19 Dec 2007
    Likes Received:


    I've noticed that a milky/oil layer develops on the surface of my water -- that the overflow does not seem to suck up.

    I also notice that this disappears with a water change but returns a few days afer.

    Any clues on what this is and how to rid the tank of it?

    feed once a day --- dry food
    2 x per week frozen food

    Tank specs:
    450 litre
    ATi 160 skimmer
    carbon/rowa - 24/7
    150w MH
    4 Ati T5 39w (2 superblue/2white)
    2 Tunze 6045 nano streams
    Resun chiller
    Aquamedic kalkwasser stirrer running with auto top-up unit
    Ph 8.2
    Salinity 1025
    Calcium 300-350ppm
    Phosphates -- dont really test
    kH -- 10
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  3. Mekaeel

    Mekaeel Moderator MASA Contributor

    Posts: 24,229
    8 May 2007
    Likes Received:
    Point Waterfront Durban

    what you gotta do is try and postion your powerheads in such a way that it blows that oily layer towards your over flow and thus skimmed out
  4. jacquesb

    jacquesb Retired Moderator

    Posts: 17,868
    29 May 2007
    Likes Received:
    Cape Town

    Hi Raveman. The reason for this is a combination of things:
    1) The water surface turbulence (the more surface water agitation, the better - so - either you must some power-heads explicitly pointing upwards towards the water surface, or have two reasonably strong power-heads pointing towards each other, that their flows converge at a certain point, which will force the water upwards creating water/surface agitation)
    2) your over flow design - how much water do you actually get from the water surface that flows down into the over-flow? The idea of the over-flow is that it does "surface skimming", meaning that only the top +-1cm of water flows down the over-flow, to the sump, where the skimmer sits - that can skim out the dissolved proteins, that is causing the oily/milky layer on the water surface (surface film)
    3) as Mekaeel pointed - you do not have power-heads that "forces" the surface water to the direction of the over-flow, that the surface film can be "sucked down" the over-flow
    4) the frozen foods that you are feeding contains too much oils/problematic contaminents (are these commercially bought frozen cubes?)

    Otherwise, you have a VERY decent skimmer.....

    If you get these things right, then your issue will be resolved!
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