I get my co2 from a local beer distributer. They want to swap the bottle so I just "rent" theirs. They charged a 30 deposit for the bottle and 15 fill it. If you are going to get co2 from a welding supply you would need your own, but most beer distributers only swap out bottles, and beer distributers are always close and convienient. I would get the large Geo. I love it . Built like a tank and was very easy to set up and dial in. This was my first calc reactor. I have the small one on my 125 and it is just cutting it. I am heavy on lps and sps .