As Tom already stated "Stability" is the real key to yeast reactor Co2 systems. I use a two bottle system 1 week apart, and rotate 1 bottle out and forward weekly. This combined with Tom's DIY reactor can actually supply some fairly respectable levels of Co2. The Alcotec Turbo Yeast primed with o2 is a quick high yield, alcohol tolerant yeast I highly recommend. HTH. Prof M