DIY CO2 and very soft water

Hi Farzan,

> I know that in order to keep the CO2 from drastically lowering the pH, the
> water should be relatively hard. However, since tetra's like soft water, My
> tank has very soft water (<30 ppm). The current pH is 7.4, temp 77 deg F,
> with amonia, chlorine / chloramine and nitrite all at undetectable levels.
> My question is, how much of a lowering can I expect once the CO2 is added?
> I do not want it to drop below 6.8, as this would be determental for the
> fish. Is there any way to control this once the reaction has started?  I am
> planning on turning on an air-stone or just disconnecting the CO2 at night.

I had 5 months ago same your problem. 
Then I started yeast CO2 with a little of pain.

The water PH is now at 6.5 and stable.
There are two possibilities to control PH:

1) Encrease/decrease the yeast quantity in generator
2) Switch an areator during night, to compensate CO2 generated from

For my tank isn't necessary any of two. The PH fluctuation from
day/night is
very little and doesn't seems to stress Tetras.

Ciao.    Ezio in a cloudy and raining Torino.

                                              ^ ^
______________________________________oOOo__( @ @ )__oOOo___________
FERRO Ezio     Torino - ITALIA                (_)

Quando il gioco si fa' duro,          When the going gets tough,
e' il duro che inizia a giocare.      the tough get going.