I use 20# tanks. One tank on a 55gal at 3 bps lasted all most two years and I think I had a small leak in the bubble counter. I have another 20# tank that I am running 3 tanks on. Two tanks at 3bps and one at 5bps. This tank is over eight months and is still at 900psi. I get refills when my tanks reach 600psi. Depending on if your CO2 system is a low or high pressure system you can go lower without worrying about a CO2 dump.
Hawk
Hawk
