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Re: Surface scum

> Date: Mon, 25 Aug 1997 11:56:18 -0700
> From: "Frank I. Reiter" <FIR at istar_ca>
> Thank you to the two people who suggested surface skimming.  As I
> understand it, the idea is simply to have the intake of a filter very
> near to the surface of the water.

Not quite.  You need to have it arranged so that the surface scum
actually goes into the intake.  Try to find a picture of a wet/dry
overflow box with comb-like slots.  The bottom of the slots are below
the surface so that the scum actually gets pulled into the prefilter. 

     __   __   __
       | |  | |
  ~~~~~| |~~| |~~~
       |_|  |_|
The Eheim "Surface extractor" does the same thing albeit a bit
differently. There is a pivoted arm with an open end that sits at just
the right height on the surface so that just surface water can flow
in, carrying the scum with it:
   ~~~~~~/ ___~~~~~~~
        / /
       / /

> This surface scum problem sounds like one that might be cured by a
> protein skimmer, but my understanding is that a protein skimmer would
> drive out the CO2 I have so carefully added to my water.  Am I correct
> about that?

There is not enough surface tension in freshwater to allow a protein
skimmer to form the fine bubbles needed to remove proteins. 

George Booth (booth at frii_com)
Need Info?  http://www.frii.com/~booth/AquaticConcepts.htm 
            * CO2 info updated 8/23/97