Cold crashing...while watching the beer consume vodka?

I'm cold crashing a 5 gallon batch now that is in a 6.5 gallon carboy. I woke up this morning to find the carboy sucking in the vodka from the air lock. I guess my question is, how do you guys handle this? Just keep topping it off? Cold crash only in a secondary? Cold crash in the keg?

 

I remove the airlock and replace it with a sanitized piece of foil.

 

yep, yep, yep, yep

 

Is there any concern of oxygen seeping into the beer with the air that gets sucked in, or will the co2 blanket protect it?

 

I wouldn't worry about it, the air will be at the top of the fermenter and the co2, which is heavier, will be at the bottom in contact with the beer. Just don't disturb the fermenter if you can help it.

 

I'll have to move the carboy from the mini fridge on the floor to a higher location to siphon. Thanks for all the input!

 

Foam stopper, a quick soak in sanitizer, squeeze it mostly dry and insert.

http://www.williamsbrewing.com/10-11-FOAM-STOPPER-P1010.aspx

 

Could also use a bubbler-type airlock (that's what I've done)- just be veeerrrry careful that you get enough fluid in the airlock so that it still works, but not so much that it will suck the fluid back in anyways...