Copyright by KD Nishikigoi 2010. All rights reserved.
||Carbon dioxide has a partial pressure in
dioxide has to go down. In water; NOT
Carbon dioxide has a partial pressure in SO.
You can have crazy CO2 levels with the air,
when oxygen goes up, carbon dioxide has
to go down. In water; NOT SO. You can
have crazy CO2 levels with high O2 levels
and vice versa or any mix.
||The most amazing myth: “Don’t
oxygenate Show Tanks” because it
blows off carbon dioxide [carbonic acid],
raising the pH and causing the ammonia
to become more toxic.
Carbon Dioxide in Koi and Fish Ponds
Written by Dr Johnson
Carbon dioxide is produced by the respiration (not photosynthesis) of both
plants and animals. When you exhale, you produce Carbon Dioxide. Pretty
much the same with fish except they don't have bad breath like you do. LOL...
One interesting thing about water is
that Carbon Dioxide levels can exist
independently from the Oxygen
concentration. For example, you can
have water with plenty of Oxygen, but
which also has a lot of Carbon Dioxide.
Carbon Dioxide likes to do one thing in water. It likes to convert to carbonic
acid. When it does this, it tends to affect pH by bringing it down into the acid
range. So, a bunch of fish breathing in a small tank with minimal circulation
and surface agitation may actually accumulate sufficient carbon dioxide to
drag down the pH due to the carbonic acid equilibrium that will result.
Removal of carbon dioxide (with its carbonic acid behavior) by increasing
surface exposure and gas exchange will remove the carbonic acid and may
raise the pH above neutral.
Do you remember in the discussion of Ammonia when I mentioned that
Ammonia is more toxic at a higher pH? Well, this created a problem for
some fish once. Someone had the idea that if you deprive the fish of
aeration, you will preserve a high carbon dioxide level. The carbon dioxide
level will keep a higher carbonic acid level, which will keep the pH down. The
lower pH will ionize the Ammonia to Ammonium and preserve the fish from
Ammonia damage at shows.
So, at least for a while, it was a widely perpetrated myth to enjoy gasping fish
at shows, and use autogenous Carbonic acid to lower the pH, rather than do
a water change to remove the threat from Ammonia.
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