The pacu is related to the piranha, but he lacks the latter's bloodthirsty reputation The pacu enjoys vegetables and can be healthy without preying on live animals. A balanced pacu diet includes commercial food, vegetables, fruit and a little bit of protein, which can include frozen or chopped meat sources.
Commercial Flakes and Pellets
Commercial fish flakes fulfill the basic needs of a young pacu and should be offered as the main portion of his diet. An older, larger pacu should be offered larger pelleted commercial food since he needs far more food to support his massive size. The commercial flakes and pellets you use should be designed for tetras to ensure they meet your pacu's nutritional requirements. Feed your pacu once per day, and give him as much as he will eat in two minutes.
In the wild, the pacu consumes large amounts of plants. You can supplement your pacu's diet with a variety of vegetables, such as lettuce, chopped potatoes, spinach, broccoli or zucchini. Just about any leafy vegetable will do, as long as he eats the amount offered within about two hours. Although this is much longer than the recommended two minutes for other types of food, vegetables don't decay and dirty the water as quickly as other foods.
You can feed your pacu small bits of fruit in addition to vegetables; however, do so in moderation. He can eat pieces of grapes, strawberries, cherries with the pits removed, or raspberries. Fruit that is soft enough to be gulped down in a single bite is best. The size of a single bite will vary depending on the size of your pacu, but a juvenile should be able to eat a whole blueberry, while an adult should be able to eat a whole grape. The thing to avoid is having your pacu rip the fruit into multiple pieces that could float around and contaminate the tank. Choose fruits that won't dirty the water or affect the pH. For example, citrus may leach citric acid into the tank if not eaten right away.
Your pacu will probably enjoy live food, but it can be dangerous to his health to feed him goldfish from the pet store. Goldfish can carry harmful diseases and pests that can spread to your pacu. Instead, feed earthworms, crickets or bloodworms. He can easily eat these live foods without any risk of illness. Your pacu might also enjoy brine shrimp. You can purchase these from retail stores or the Internet; you can buy them live or hatch them as needed.