"default" wrote in message
ups.com...
I just started a C02 setup with a bottle. I've closely monitored it
for two days and it looks like this:

Initial parameters:
pH 7.4
KH 40 ppm
C02 calc 2.6

At the end of the first day, in the evening:
pH 6.7
KH 40 ppm
C02 calc 13.1

5:00 next morning (C02 is off at night, 1 hour after lights out)
pH 7.0

Later that day pH dropped down to 6.6 for a C02 calc of 16.5

Is a swing from 7.1 to 6.6 on a daily basis what others see? Should I
keep the C02 on all night long? How much lower will I expect the pH to
drop if I leave it on all night while the plants don't eat it?
thanks,
steve
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looks good to me. If you are shutting down your CO2 injection at night then
the PH is going to rise and then lower again during the day when you are
injecting. PH swings without an accompanying swing in hardness will not
cause undue harm to your fish so stay away from buffers. Personally I leave
my CO2 on 24-7 and shoot for about 25-30 PPM. In the morning my PH is
slightly lower and rises a few points during the day as the plants uptake
the co2. I don't see quite as much a swing as you do but I wouldn't be
worried about it as long as when the lights are on you are maintaining 25-30
PPM of CO2.

Rick