So, I'm dumb and bought a 23 liter carboy thinking it was 5 gallons. Racked into it recently as a secondary because I'm racking onto an oak dowel (will later be used for a 3 gallon carboy as part of a stopper for a lambic. Just "seasoning" it
) and aging it for a couple more weeks than I'm comfortable with doing in a plastic bucket primary. Whoops, there's a lot of head space.
With my equipment, I believe I have three options:
1) Do nothing and hope that off-gassing will create enough co2 to fill the space. It will only be there for 2 weeks most likely. (Probably not a great option)
2) Brew around a gallon more of the same gravity with pilsen DME and hop it to the same IBU's (The recipe is mostly pilsener malt with some spelt).Rack into the carboy and let it do its thing.
3) Rack again into a 3 gallon carboy I have and bottle the rest now.
Any advice is most welcome! Pic below to help in decision making