I use Fleischmann's "Active Dry" yeast, so this information may not be
relevant to you, but here goes anyway ....

I use two 64 oz. juice bottles to supply DIY CO2 to my 29 gal heavily
planted tank. I have the tubing "T"ed together and going to a Hagen Natural
Plant system diffuser. Each bottle has a mixture of 2 cups sugar, 1/2 tsp
baking soda, and 1/4 tsp yeast, which I've found I need to let sit for about
a day after mixing before I get optimum output.

I swap out the bottle containing the oldest mixture every three weeks ... I
just thrown the mixture away and replace the bottle with another one
containing a new mixture that's been sitting for a day. I get fairly
consistent CO2 production this way. The one issue is that the room
containing the tank can get fairly warm during the summer if my wife chooses
to not use the a/c that day ;-), and this increases CO2 production quite a
bit. I used to use an air pump on a timer to control pH drop at night, but
was never able to get it adjusted quite right, and this also didn't address
the warm-room-during-the-day issue. So now I use a CO2 controller, set to
turn on the air pump when the pH drops too low.

"Dances With Ferrets" wrote in message
om...
For any who may be familiar with the 2-liter-soda-bottle method of CO2
production... using baking soda as a buffering/stabilizing
compound... Could someone tell me what the optimum mix of water,
yeast, and baking soda would be using this method? (in case it makes
a difference in the formula, the yeast culture in this case is an
ethanol-resistant strain commonly used in wine-making). Also, how
often would one recommend refreshing the solution in the bottled
culture? Or would it be best to discard the culture and start a new
one? If discarding, how far in advance should the new culture be
started to supply a consistent amount of CO2?