Cooking fish seems easy enough — until you have to check to see if the fillets are done. Letting them cook too long makes the fish dry and chalky, while undercooking it results in firm flesh that could make you sick. The good news: You can avoid both cooking mishaps simply by taking the fish’s internal temperature. Once you know the correct temp for the type of fish you’re cooking, it allows you to serve up scrumptious filets of salmon, halibut or cod without hassle.