That all being said, I did once take a 45/45 tank and swap out teh regulator for a CO2 antisphon valve and had a 45/45 carbon fiber tank that held CO2, so I guess you could use the tank, but you'd need to replace the regulator in the tank with a CO2 anti-siphon valve. Those usually have on/off's vs pin valves already. You may have a hard time however finding a shop willing to fill it.