Originally Posted by odedald
Thanks for your answer.
About 1. can you expand a bit?
Not to speak for the guy, but during the fermentation process oxygen is pushed out of the headspace in your fermentation vessel by CO2 (given off by the fermentation). So basically that headspace is then filled with CO2.
I think his thoughts are that with such a large fermentation vessel, you might not be filling up the entire headspace with CO2 thereby leaving some oxygen that could oxidize the beer.
I don't really agree. During primary there's so much activity going on, I feel like your 15L of headspace will most certainly fill up with CO2. Of course I don't really have any scientific proof to give you on this, and I'll probably be corrected if I'm wrong.
Maybe if you were using that vessel for secondary though, that might be a problem.