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Re: CO2 controller...

At 03:48 AM 3/29/01 -0500, Booth wrote:
>By equating our aquariums to natural ponds, you seem to be implying that the
>pH in natural ponds goes through wild gyrations on a daily basis.  More to
>the point, you are implying that big changes in CO2 concentration occur in
>natural ponds, causing the huge pH swings, and fish and plants are not
>affected. You may even be implying that huge pH swings are required for
>proper fish and plant health and we need to get more elaborate pH
>controllers capable of both lowering *and* raising pH to mimic these swings.

First you asked about numbers.  I am talking about ponds in the 1-100 
acre-foot category.  I am talking about daily pH swings.  I am talking 
about swings from 7.x to 9.x.  I am talking about CO2 levels that top at 
maybe 5ppm and minimum at maybe .5ppm.

Given that, I claim that likely our plants and fish are adequately adapted 
to deal well with swings of a few tenths of a pH point.  Do you have any 
scientific evidence to refute that?

 > If a huge pH swing (or a huge increase in CO2) is so harmless, why did 
your fish die?

George, I have explained this several times on the list but perhaps you 
missed them.   The model for gases in gaseous state is way different from 
the model for gases in aqueous solution.   In solution, gases behave pretty 
much independently of one another.  In the gaseous state, the sum of the 
partial pressures of the constituent gases equals the "atmospheric" 
(ambient) pressure.   So in the "air" space over our tanks, there IS 
competition between gases.   If you blow a lot of CO2 in there, you will 
drive off ALL oxygen.  If you have no air pump/trickle filter/whatever 
running to re-add O2 to your water and your lights are out so your plants 
are not producing much, your fish will die of anoxia.   Got it?

Dave Gomberg, San Francisco       gomberg at wcf dot com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam