I have a co2 generator, but haven't decied how to control it yet. As far as I know there are two ways. Have it shut off by PPM, or by time. The controler to use PPM is about $450. The cyclestat (for time) is about $150. I would much rather use PPM control.

Also, search tel-air ventostat, A cheap way to use PPM. I bought all the stuff for this, but I can't figure out how to put it together. It requires some wireing and stuff. There are (or were) people in this fourm who directed me to that, so I assume someone here knows how to hook it up.