High Quality Content by WIKIPEDIA articles! Pacu (Portuguese pronunciation: ) is a common name used to refer to several species of omnivorous South American freshwater fish that are related to the piranha. Pacu and piranha have similar teeth, although the difference is jaw alignment; piranha have pointed, razor-sharp teeth in a pronounced underbite, whereas pacu have squarer, straighter teeth in a less severe underbite, or a slight overbite. Additionally, full-grown pacu are much larger than piranha, reaching up to 30 kg (60 pounds) in weight, in the wild.