RE: NANFA-- weird darter illness?

Crail, Todd (
Mon, 13 Jan 2003 11:45:10 -0500

Yes. Maybe I didn't clarify that well enough. I guess the "bacterial
respiration" was to demonstrate what happened to the little O2 that would be
left, and the fish would be ingesting a much greater proportion of CO2 and N2
per unit of O2, which is bad bad bad.

In a planted system, there was an excess of O2 at the end of the photoperiod
that is observable in the rise in pH, which carries the system's respiration
thru the constant CO2 supply. Not to mention, the rise in pH converts much
more of that gas CO2 into bicarbonate, which is less reactive... But that's a
whole other 3 paragraphs I shouldn't type while on the clock :)

-----Original Message-----
From: Nick Zarlinga
Sent: Monday, January 13, 2003 11:18 AM
Subject: RE: NANFA-- weird darter illness?

Todd, one thing to remember is that O2 levels are independent of CO2 levels.
You can have a high O2 concentration with high CO2 levels also. The amount
of CO2 that is required in a plant system is not detrimental to fish. The
problem is when the CO2 is still added at night, and the plants and animals
are using the O2. Then the CO2 can be very dangerous, as you pointed out.

Nick Zarlinga
Aquarium Biologist
Cleveland Metroparks Zoo
216.661.6500 ext 4485
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