Substituting fish for ground beef to your tacos is an easy way to make tacos a healthier meal. We recommend using tilapia. For this recipe take about 6 6oz tilapia fillets and spice them up with your favorite Mexican style spices. Now toss them on a hot grill for a few minutes on each side. Fill the soft flour tortilla with some lettuce, cucumber, radishes and lime juice – sour cream is optional.