Carboy Question

[Haldedrums]

Is a 6 gallon carboy big enough to ferment 5 gallons batches? In other words, is a gallon worth of head space sufficient enough space to supply oxygen to the yeast?

Secondly, is a carboy stopper with a hole for a water trap a good setup for fermenting?

 

[Nurmey]

Yes to both questions.

 

[Revvy]

Yes, I've never had an issue.

 

[Catt22]

Yes, sort of. The head space has little to do with supplying oxygen to the yeast. Typically, that is done prior to pitching by aerating with either pure O2 or air. Some head space is desirable so that the krausen (foam) produced during active fermentation has room to expand without blowing through the air lock. A blow off tube can be used if the head space is not sufficient to contain the froth.

Yes, most use a stopper and air lock as you have described. The alternative (one at least) would be to use a blow off tube as I mentioned above.