I just recently went back to the red O2 tank + SS stone method after years of using an aquarium pump/HEPA filter. This time though, I picked up a flowmeter to measure out the O2 rate.
The
Yeast book noted that around 9-12 ppm O2 was optimal and was something you just couldn't get using atmospheric air (aquarium pump, shaking, etc).
I don't have the book in front of me now but I'm guessing it was White Labs that did an experiment where they measured O2 content in 5 gallons of wort after a set amount of oxygenation: 1 min, 2 min, etc. at 1 L/min. I think the 1 L/min for 1 minutes (basically 1 liter of O2) yielded 12 ppm O2.
The authors recommended a trial-and-error approach to dial the oxygenation rate in, assuming that people understandably didn't have a method to measure O2. Personally, I don't have the time or patience to experiment with getting oxygenation right.
For my 10 gallon batches, I've been adding 2 liters of O2, mainly at 0.5 L/min for 4 minutes because the 1L rate is pretty intense and causes a lot of foaming. Even at 0.5 L/min, the flowrate seems high. It foams and you can see the surface disturbance. I believe though that the O2 is trapped in the bubbles and that as the yeast goes through lag phase, it scours up the O2 in the headspace.
So far, the results have been really, really good. I'm getting far more consistent attenuation than I did with air.
Anyway, this went a little off track from the disposable O2 tank thread. Sorry.
To answer Sarrsipius, I've had this O2 bottle for a while. I think I've gotten at least a dozen batches out of it.