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Re: Oxyen levels

Someone was asking last week about the diurnal fluctuation of O2 levels in a
CO2 injected tank.

The  tank is a very heavily planted 120 gallons with a moderate fish load.
The tap water is pH 7.6 to 7.8, Carbonate is 4 degrees hardness.

Tank water: Temp. 80 degrees Fahrenheit
CO2 injection goes 24 hours per day with no fluctuation regarding bubbles
per minute.

before lights out pH is 6.85  O2 is 11mg/l
before lights on pH is  6.74   O2 is 8mg/l

There is no surface water movement over most of the tank.  Very little at
one end.
Carbonate is 3.75 degrees hardness in the tank.

G. Kadar