In large mixing bowl, add beer, baking soda, salt & pepper, and egg. With a whisk, slowly add enough flour until the batter is thick, not runny and adheres to a wooden spoon. Heat oil in a deep fryer or in a deep sided sauté pan to 350 degrees.
Dredge fish in flour, shaking off excess and dip in batter, covering all sides of fish. Holding battered fish, gently dip into hot oil, holding halfway in, wait 15 seconds and drop into oil. This will prevent the fish from sticking to the bottom. Flip fish over when brown on one side and cook altogether about 6-8 minutes, depending on the thickness of filets. The fish should be all one color all the way thru or 140 degrees internal temperature.