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I'll see if I can add what I know.
Protien Skimmer (or Foam Fractionators) won't work in fresh water due to the
viscosity of the water. Salt water is much thicker (?) or more viscous than
fresh water, therefore it is much easier to produce foam. Look at a beach
versus a lake shore. You see much more foam at the sea shore. Objects in
salt water float much better, and higher in the water, then freshwater due
to this principle.
Also, the skimmers work by attracting aqua phobic molecules. Since they
don't want to be in the water column, they happily adhere to the tiny
bubbles in the skimmer and ride their way out of solution. In fresh water
it is much harder for these molecules to get out of solution due to the
viscosity of the water.
I hope this adds to the discussion, and doesn't subtract from it. I am
going on what I can remember.
I'm sure any search engine could lead one to the correct answer. In fact, I
believe this subject had been covered here on the APD, so check the
spicolte at hotmail_com
>Date: Sun, 21 Jul 2002 16:32:37 EDT
>From: Dgrim62 at cs_com
>Subject: Re: Protein skimmers in planted tanks.
>I'll try this one.
>Protein skimmers work by producing a fine mist of bubbles either by venturi
>action (using a water pump) or by the use of diffusers that produce a fine
>mist of bubbles (using an air pump). There are different designs that
>to prolong contact time between the water and the bubbles.
>The organic mulm (detritus) present in the water column has not decayed to
>ammonia yet, and attaches to the fine bubbles in the skimmer. This forms a
>foam that collect in a cup, in most cases. I'm not sure why the organics
>drawn to the bubbles, electrical charge perhaps? You are, in effect,
>organics before they degrade to ammonia, etc. Much of this is ultimately to
>prevent the production of nitrate, as algae is the bane of all reef
>and nitrate is a great algae food, and can cover corals and destroy reefs
>Protein skimming is not effective in freshwater aquaria, I am guessing
>because of the relatively less amount of ions in solution in freshwater as
>opposed to saltwater. I would guess it is the ionic activity in the NA+ and
>CL- of the salt in water that makes skimming effective in salt water.
>I would guess (again) that the net effect of protein skimming in fresh
>would be a higher dissolved O2 content and possibly CO2 off gassing because
>of the increased water turbulence.
>I kept reefs for many years, and never really cared to explore the chemical
>whys of skimming. I just know it works.
>If you have ever observed an UG filter in saltwater vs freshwater, the same
>airstone seems to give finer bubbles in salt vs freshwater.
>Once again, I am happily corrected if anyone knows different.
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