I finally got my hands on a 10lb co2 cylinder and the appropriate regulator with a solinoid to shut it off at night. My next question is: What is the best way to inject the CO2 into the water. I've used a simple hagen bubble ladder in the past, but after reading the posts here, I've switched to a coralife wooden 'airstone' that gives off very small bubbles. This seems to work well, however I'm intrigued with Tom's venturi design and am wondering now if I should give the venturi a try. In your experience, would it make much of a difference to the bottom line of growing plants?

Thanks for all your help so far. It seems the more I get addicted to this hobby, the more questions I need answered.