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Thread: Rainbow on top of water

  1. #1
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    Default Rainbow on top of water

    Every now and then I get a rainbow effect on the top of my water does anyone know what this is does not seem to hurt my fish but curious as to what this is . Thank u

  2. #2
    Registered Member Shan_Evolved's Avatar
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    Shan

    Default Re: Rainbow on top of water

    Like rainbow as in on top of your water surface? Like oil?

    Does not sound good at all unless its lighting related. I would get on that asap
    Amateur discuskeeper, Professional doofus

  3. #3
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    David

    Default Re: Rainbow on top of water

    What type of lights are you using?

  4. #4
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    Default Re: Rainbow on top of water

    what the temp. of the tank? Ed

  5. #5
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    Default Re: Rainbow on top of water

    Hi Springer,

    The rainbow is a surface film formed from protein/oil which has yet to break down to other pollutants. In saltwater it is removed by a protein skimmer at this point. The surface tension of freshwater is different so a skimmer is inefficient.

    The film can have two negative effects. First, it can break down to pollutants as stated and second, it limits gas exchange between water and air. Not Good.

    I feed heavily so I monitor surface film. When I do a water change, I first siphon the bottom of the tank (future surface film) and second skim surface film with a cup just SLIGHTLY tipped into the water in a slack area. You can see the film race over the lip of the cup. Lift the cup out before it fills completely or else the film immediately returns to the tank. You will notice that your fish/tank are doing best when there is little or no surface film.


    Hope this helps,
    Andy
    Last edited by andy77; 04-09-2021 at 12:06 PM.

  6. #6
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    Bill

    Default Re: Rainbow on top of water

    Agree with andy77.
    Also when doing a wc and filters "off" (keeping water turbulence to an absolute minimum) use a paper towel and spread out of top of water. Helps absorb that oil slick

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