I checked on my fermenting brews and found the Skullsplitter had overflowed and popped its air lock off. I cleaned up the mess, refilled the air lock and got it bubbling again. Hopefully the thick crust of foam on the top of the beer protected it from too much oxygen, though I read recently that additional oxygen during the primary ferment can push the yeast into a mode where they produce less estery beers. It's a curious idea. This batch needs more constant supervision than expected.