so i just racked my AG pale ale into a secondary after 21 days in the primary and the air lock is bubbling away again about once every second even tho i have hit my target FG. Can any one explain whats going on? Is it fermenting more?
There's Co2 trapped in your beer that hasn't been released. Whenever you move the beer, it gets released. It's normal to see bubbles when you rack your beer.
21 days in the primary should have finished fermenting a while ago. The only way to know or sure is to take 2 gravity reading a couple days apart. If they are the same fermentation is over.
More than likely, the bubbles you are seeing is escaping co2 gas after racked to the secondary. Totally normal.