Looks like a pacu to me:
And they are vegetarians!
Comments. The Pacu, shown above, is a very large Pacu about 30" total length and heavy. It's probably not a Red Bellied Pacu; more likely it's a Black Pacu. All Pacus grow very fast to very large sizes. They can eat almost any food, and are now being raised in huge fish farms throughout the world as a food fish.
Pacus are relatives of the Piranha, and Pacus look like Piranhas. But Pacus are mainly vegetarians that will adapt to eat almost anything. In the wild they eat very hard nut-like vegetation that they crush in their powerful mouths. Pacus are not recommended for most aquariums because, when given proper care, they will quickly grow to a very large size.
Several years ago the government of Brazil set-up a fish farm to spawn and release Red Pacu. This fish farm was very successful at spawning the Red Pacu, and the Red Pacus spread to many other fish farms all over the World. A consequence of this flood of Red Pacus is that other Pacus, such as the Black Pacu, are very difficult to find now.