For a primary fermenter, I use a plastic pale. One time when my air lock wasn't bubbling, I found that air was escaping from around the gasket in the grommet hole in the lid, rather than going through the air lock. I jammed the air lock in further and the beer turned out fine. Then I replaced the gasket.
Owner, Brewer, Taster
Drinking: Fat Guy Porter, Fat Guy Tire, AJ's Raspberry, SWMBO Slayer
Up Next: Xmas Ale