CO2 Advice

Does someone want to give advice on setting up a CO2 system? What in your opinion is best? Heats an issue, so if a tank is good and can be turned on and off with the light cycle, I'd be willing to listen. Im sure a tank is safer too. I'm thinking propane might be the most cost effective though. I'm starting to plan out sealing my room for AC and need to figure out the cO2 component. Any advice, or tutorial links, etc... would be much appreciated.

Cheers!

My 5x5 tent uses a 20lb tank in about a month, the air is purging about every 45 minutes. It seems fine for now. If you just want to try it out, it seems like tanks are a better option... you can probably sell your tank for 2/3 cost if you decide to upgrade to gas. Also, you're going to want to seriously consider getting a controller.