I found a 2.5 lb CO2 Cylinder used, how long will one last on a 220 Gallon tank with plenty of acros ? Guy is also talking about when the last "hydro" was ? What is he talking about ?
how long it lasts depends on your reactor and how you use it.
I would think not very long with your setup
The "hydro" he is talking about is a certification test that all gas cylinders must pass every 1, 2 or 3 years (depending on your state) before a provider will fill the tank. The date is stamped into the tank.