> If you are continuously bubbling CO2 (24-7) then 3 months is pretty average, > IMO. The average for a 20# tank seems to be about a year, although this also No. My #5 bottle is running thru Dave's system 24/7 for 10 months now, at 40 bubbles/min. I recall reading somewhere that the average 5# bottle should last way more than one year at those rates. - Ivo Busko Baltimore, MD