Last night I started on a 3 gallon batch of ceyser. I used 2 gallons of apple cider sweetened with sugar and then, for the 3rd gallon, used a honey/water mixture from a mead recipe. I pitched the yeast, put the airlock in place, and went to bed.
When I woke up this morning, I saw that it must've bubbled up a lot overnight. The batch seeped through the rubber stopper, completely filled and overflowed the airlock, and dripped down the sides of the carboy leaving a sweet sticky ring on my floor. I cleaned everything up and it hasn't overflowed since then, but I'm not sure what to do about the airlock. It's still filled with the cider/mead batch. Should I empty out the airlock and refill it with water? Or is there harm in leaving it be? I've never had any need to readjust the airlock in the past, so I'm not sure if I should mess with it now.
And just because I have it, here's a celebratory photo I took of the batch last night.