Soak 3 pounds of fish fillets in buttermilk to cover. Refrigerate in covered container with 1 lemon sliced over it for 2 to 3 hours to remove fishy taste. Heat 3 cups oil in heavy 2 1/2 quart saucepan. Drain off milk. Cut fillets in half and dredge in white flour. In another bowl, combine 2 cups pancake mix and 2 1/2 cups Club Soda to give the consistency of buttermilk. Dip floured fillets into batter and let excess drip off into bowl. Deep fry 4 minutes each side and keep warm in 250 degree oven until all pieces are fried.