FROZEN TILAPIA FILLET is a variation of frozen seafood. Tilapia are mainly freshwater fish inhabiting shallow streams, ponds, rivers, and lakes, and less commonly found living in brackish water. Tilapia is a pretty impressive source of protein. In 3.5 ounces (100 grams), it packs 26 grams of protein and only 128 calories. Even more impressive is the amount of vitamins and minerals in this fish. Tilapia is rich in niacin, vitamin B12, phosphorus, selenium and potassium.