I started a 55gallon planted tank about 2 months ago, not my first planted tank, but first time using pressurized CO2. I got a regulator off a guy who had been using it on a paint ball cylinder, it had a needle valve and a bubble counter and he had swapped out one CFM gauge for a psi one.. I didn't want to use a paintball cylinder so I got a 20lb cylinder(smallest I could get). I have been running it for 2 months now at around 20psi, all of a sudden the tank seems empty, it was at 15psi this morning and I cannot increase the pressure. The main gauge reads 0. None of my fish are dead and the level in the fish tank appears safe. I leak tested it the first couple weeks I had it and again just now for what good it would do. I am really confused, because I know a 20lbs tank should have lasted much longer. I suspect it's leaking, but why wouldn't the leak bubble? I soaped it up all the way to the reactor.