Splitting 5 gallons into 2 secondary fermentations?

Hey all. I started making a stout a couple days ago, and it's in the fermenter now (5 gallons). My plan all along was to try adding coffee to secondary fermentation, but I'm wondering if I can get away splitting the batch into two secondary fermenters and adding the coffee to just one of them. That way, I can see exactly how the coffee affects the beer (and if I totally over/undershoot the amount of coffee I should add, I'm not stuck with 5 gallons of it).

My issue is that I only have 5-6 gallon carboys. Is it a problem to move only 2.5 gallons of beer to a 5 gallon fermenter for secondary? I can't think of a problem off-hand, but I also don't know very much yet about how this all works.

Thanks!

Andini said:

My issue is that I only have 5-6 gallon carboys. Is it a problem to move only 2.5 gallons of beer to a 5 gallon fermenter for secondary? I can't think of a problem off-hand, but I also don't know very much yet about how this all works.

Thanks!

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How about too much headspace?

At that stage of the fermentation, it's not kicking out much CO2. The empty space in the carboys is going to be mostly air for a while. I'd be concerned about oxygenation.