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.

I`m much happier with my reactor than a simple diffuser. That said, you could also use a powerhead to blow the bubbles from your diffuser into the plants. That seems to be what works best but I do think the venturi reactor is much better than simply letting the bubbles rise to the top.

Well, you can use either, but given the stuff you have, you may just want to use the limewood stones, blast the mist around with your filter outflow in a downward direction into the plant beds.

But the DIY reactor is also cheap and fun to watch and works very well also.
Turn the CO2 off at night though.

Regards,
Tom Barr