I finally took the plunge and bought a CO2 system. I got Dave Gomberg's system, I think it is a good buy. I got a 5lb tank from a welding supply shop, for $55. So the whole system is around $140. It only took a few minutes to get the system connected and running. After a day, I could see some plants bubbling. I'm very happy with the system, and recommend it. Sherlock Wong