Deep-fried fish and seafood can be light, crisp, and wonderful, or heavy, soggy, and greasy. Making the right choices and using the proper deep-frying techniques and tools can make all the difference. For successful deep-frying, you will need a heavy, deep pot, high-heat oil, a thermometer, tongs or a spider to remove fried items, and an area to drain the cooked seafood.
Choose the Right Oil
The smoke point of an oil is the temperature at which it begins to break down, give off acrid smoke, and become unusable. When deep-frying, choose an oil with a high smoke point (peanut, grapeseed, safflower, soybean, sunflower, canola, and extra light olive oil are all good choices) with a flavor that is either neutral or appropriate to the type of food you're cooking. Don't use unrefined oils for deep frying, as their smoke points are much lower.
The Right Pot
Using a heavy, deep pot is best for deep-frying. At the minimum, the pot should hold about 3 inches of oil and have at least 3 inches of space above the oil line. The larger the pot, the more you can cook at once.
Use an Oil Thermometer
There are many ways to estimate whether an oil is hot enough for frying (bread cubes, a pinch of flour, chopsticks), but there is only one way to know the right temperature. An oil thermometer is inexpensive, but invaluable when deep-frying. If a recipe doesn't specify a temperature, 350 F is a good choice for deep-frying most fish and seafood.
Don't Crowd the Pan
Putting a lot of food into the oil all at once can lower the temperature drastically and allow oil to seep into the food, resulting in greasy and heavy food. Frying in small batches produces much better results. A good rule of thumb is to not use more than half of the surface area of the hot oil. This will ensure plenty of room for the food to cook.
How to Remove the Food and Drain It Well
A skimmer, spider, or even a slotted spoon can be used to remove the cooked food from the oil. Fried fish can often be delicate, so treat it gently as you move it from the cooking pot to the draining area. Traditionally, paper towels, brown paper bags, or paper plates were used for draining fried foods. A better idea is to use a rack. A roasting rack or cooling rack (used for baked goods), placed over a rimmed baking pan or sheet, will allow fried foods to drain and help them stay crisp, too (if you do use paper towels, be sure to use only plain, unprinted towels).
Keep Your Food Warm
Before you start frying, turn your oven to the lowest setting. Once your first batch has drained, place already fried foods on a rack, then transfer it to the oven while the next batch is frying. Once you've finished cooking, enjoy your food and dispose of the used oil safely.