5 gallon vs. 6 gal carboy for secondary

So I'm thinking about buying a carboy mainly to be used as a secondary/clearing vessel. But I'd also like to have the option of using it as a primary fermenter without having to use a blowoff tube, so I was going to get a 6 gallon better bottle, but the lady at the LHBS said if I'm going to use it as a secondary, I'm going to want to get the 5 gallon size. Does it really matter? Is having that much more headspace really going to oxidize my beer? I can't imagine it would.

Doesn't matter. CO2 is heavier than air, and even in the secondary, your beer will be giving off a little CO2.

Sea said:

Doesn't matter. CO2 is heavier than air, and even in the secondary, your beer will be giving off a little CO2.

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That's exactly what I was thinking. It seems to me that even if it's "done" in the primary, racking to the secondary would likely stir up the yeast just enough to help it produce a nice CO2 blanket to protect my beer regardless of how much headspace I have.

Thanks!

you will also release Co2 that is dissolved in the liquid also. Just like shaking up a pop can.

I agree it does not matter.

I use a 6 gallon secondary, just for those rare cases where I might add some fruit or other adjunct in the secondary - I don't want it to spill over. In contrast, I use a 5 gallon primary with a blow off tube to eliminate some of the excess trub.

Cheers,
Brad

I have two six gallon Better Bottles and use them for both primary and secondary. It's never been a problem.

I have one of each and so far have used both as a secondary, but only the 6gal as a primary.