I needed to get my 20 lb. CO2 tank filled. I searched the internet and found out that the Colorado "green house" people use CO2 to make their plants grow faster. I found a place called Way to Grow located on Sinton road South of Garden of the Gods road, it is next to the Department of Wildlife building. They were going to swap my tank, but they didn't have any that were full. The guy filled mine and charged me $7.52. That is about $10.00 cheaper than Airgas or Colorado Welding Supply.