Just as an experiment, I grabbed a 7oz paintball tank out of the garage. It's been in there for years, and it's still got CO2. I screwed on the filling station adaptor, which has a "wheel". I attached a 3/16" barbed nipple (for airtools), attached air pump tubing and a check valve. Stuck the tubing up the intake of a powerhead and stuck it in a 10g tank. Playing with the wheel on the fill station, it got the flow just barely coming out. The power head blows a mist of CO2 every minute or so. I can watch the CO2 moving up the line slowly until it sprays, water gets back into the line about 2.5inches, then it starts it's slow march toward the powerhead again. It's been going for almost 24 hours now.