"Nikki Casali" wrote in message
...
George Pontis wrote:
You do not require an automatic pH
monitor/controller. Instead you can set it up at some initial rate, say 1
bubble every two seconds, then adjust up or down as needed to get to the
level you seek. If you know your KH, then you can determine CO2 by
measuring pH using your favorite test method. It may take a small
adjustment once or twice a day for three days to establish your setting,
but once done it will remain stable.

I find my that bubble rate varies depending on ambient temperature. The
higher the temperature, the lower the bubble rate. One day, I set my
needle valve for 2 BPS. Ambient temperature was 25 degrees C. The next day
the temperature rose to 30C. I got 1/2 BPS. I set the bubble rate back to
2 BPS. The day after it went back down to 25C. The bubble rate was now 4
BPS. This must be something to do with expansion of metal parts or cheap
CO2 valves. I'm not sure if this is everyone's experience, but I have to
use a pH controller to keep the pH stable. It was just far too much stress
without it.

Nikki


I had real problems with my first needle valve, it would not stay consistent
at all. This caused large PH swings, as the bubble count was always falling
off. The company finally replaced the whole regulator and it does seem
better. But I purchased a PH monitor long before the replacement arrived.
It's worth the extra
cost for the peace of mind (at least for me). I expect more expensive needle
valves may be less problematic.