[GSAS-Member] CO2 displacing O2 myth

["Paul M. Wallace" <pwallace@u.washington.edu>]

The myth is that adding CO2 drives out O2.  I would like to add the other
perspective:

Due to chemistry, CO2 and O2 do not displace each other at the
concentrations we run.  From 
http://fins.actwin.com/aquatic-plants/month.9812/msg00530.html (Karen
Randall in 1998)

"CO2 and O2 do not displace each other at the levels we want in an aquarium.
 Saturation in a typical tropical FW aquarium is a little over 8 mg/L. (it
will be a little less at the warmer temps in a discus tank)  My high growth
CO2 supplemented tanks run at about 11 mg/L O2 during the photo period, and
drop only to about 8 mg/L over night. (with the CO2 still running)  You'll
be hard pressed to maintain O2 levels near that in a non-planted tank, no
matter how you aerate it."

The old rule of thumb is listless at the top -> low O2.  Listless at bottom,
high CO2.

-Paul

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