How long will a 2 1/2 lb tank last? I have only 18" between the bottom and the shelf on my 30 gal stand which is not enough space for a 5 lb tank. I could move the shelf but it will be a job to do so I am thinking abut the smaller tank.
It depends on how often you are willing to drive to the local welding /gas supply to have it filled,your fish tank and co2 set system will be moved to different places through out the life of your co2 tank ,so design/buy your set up for the future not just the time being.
actually my 2.5 is alot smaller than a my 5 lbs. Both are aluminum.
As for how long it will last, that all depends on the bubble rate as they said above. For a 20 gallon tank mine lasts 3-4 months. What size tank are you planning to use it with? If it's a 55 gallon or higher, it likely won't last very long.
Well lets see, I am 75 so the tank won't be moved probably ever. The tank and stand are about 20 years old so I have to work with what I have. 30 gal long tank 36". According to what I can find the 2 1/2 is 4 1/4 dia X 14" tall and the 5 is 5 1/2 dia X 18 1/4 tall. The stand is wood and would require raising the shelf 2 to 3 " to get 20 t0 21" for the tank. I have calculated the water volume to be 24 gal after the substrate etc. If it will last as long as 3 to 4 months then I will go with a 2 1/2. CO2 fill station is less than a mile away.