Wine/champagne yeast is the way to go. I use Lalvin EC1118(Champagne) or
Lalvin K1-V1116(white wine) which last me 5 weeks! I use a heater as well
to keep the temp above 20C. Otherwise try to get a yeast with a high
alcohol/sugar tolerance otherwise it'll produce inconsistant bubble
production or go kaput at 3-5% alcohol(1-2 weeks) using standard bread
yeast. I've read Fleischmans is supposed to be a good bread yeast if you
can't get your hands on the wine yeasts.

"Ryanw1234" wrote in message
om...
I currently use 2 1.87L bottles for my yeast production. I can keep
the CO2 levels up around 20ppm or higher for the better part of the
week. But when I hit about the one week mark my yeast production drops
way off, like to the point where its only 1 bubble every 15 seconds.
This is the same with both bottles. I have tryed changing all the
variables to make it go longer. These bottles where both started at
the same time. Im thinking the only thing that it could be is the
yeast..Should I try a different type...or is there something else that
im missing?

Thanks
Ryan Wilson