On Sun, 26 Jan 1997 03:39:02 -0500, Aquatic-Plants-Owner at actwin_com wrote: > How long is a lifetime of a 20lbs CO2 tank? Well, the molecular weight of CO2 is about 44, so it weighs about 2g/L. So 20# is about 4500L or about 1000 gallons of CO2 at normal conditions. If you use a gallon a day it will last 1000 days. Different rates, different durations. Dave Dave Gomberg, FormMaestro! San Francisco CA USA gomberg at wcf_com