As a rule of thumb, 1-inch thick fish fillets will take no more than 10 minutes to cook (longer if the fish is thicker). Fish is ready when the meat turns from translucent to opaque and flakes easily at the touch of a fork. If you’d rather not eyeball it, you can use a meat thermometer to remove the guesswork. Cooked fish will have an internal temperature of 145 degrees F, but keep in mind that, like any other protein, fish will continue cooking even after it’s removed from the heat. So, I typically cook the fish to a few degrees under its ideal temp, and let it finish cooking at room temperature.