this is going to sound strange, but go to reefcentral.com, look up a area reef club, and search posts for used calcium reactor equipment. Lots of people get out of the reef aquarium hobby, and dump there gear. CO2 is used for reefkeeping with calcium reactors. So search calcium reactors on the local reef club site and you should find some cheap co2 gear.Can someone point me toward a site that has reasonably priced CO2 injection systems. $150.00 or less and a 20lb aluminum tank for $100.00 or less. Thanks in advance.