There are a few pro tips for keeping any fried foods crispy, including beer battered fish. You'll need to control several variables: temperature, ingredients, and cooling. The batter needs to be very cold, and the fryer must be preheated to 350F. Add a little cornstarch to the batter to absorb extra moisture and keep things nice and crispy! After you remove the fish from the fryer, place it either on a paper towel-lined plate or, if you're baking a bunch, place a wire rack over a baking sheet. This will let any extra oil drip off and keep the crust nice and crunchy. If you do all of these things right, you'll have perfectly crispy fish every time.