I’ve had an IPA in secondary for about 2 weeks and noticed that there are fruit flies swarming around the airlock. I used a (sanitized, clean) knee-high as the hop bag and tied it around the neck of the carboy and then put the airlock in (tightly). I didn’t notice where the fruit flies were coming from until a couple days ago: beer seems to be wicking-up through the fabric of the knee-high and up past the neck/airlock and the little buggers are really enjoying it.
I don’t see any of them inside the carboy itself but I’m wondering if anything could get into the beer to infect it. I’m planning on bottling the beer this weekend and haven’t opened the airlock (to taste the beer or take a gravity reading) for fear the b4st4rds might find their way inside.