What is the difference between a pacu and a piranha?

difference between pacu and piranha As we plunge into the fascinating realm of aquatic creatures, the distinction between pacus and piranhas becomes a subject of intrigue. These two South American fish share a familial link, yet their differences in physical attributes, behavior, and dietary habits paint a diverse picture of the underwater world. In this exploration, we navigate the waters of piscine taxonomy to unravel the disparities between the pacu and piranha. From their distinct teeth structures to variations in size, behavior, and preferred habitats, understanding these differences is not only essential for the discerning aquarist but also unveils the remarkable diversity that thrives in the freshwater ecosystems of South America. Join us in this aquatic odyssey as we delve into the nuanced distinctions that set the pacu and piranha apart, offering insights that illuminate the captivating world of these remarkable fish.

The primary differences between a pacu and a piranha lie in their physical characteristics, behavior, and diet.

Species Classification:

- Pacus belong to the genus Piaractus and are part of the family Characidae (characins). There are several species with P. brachypomus (Pirapatinga or red-bellied pacu) being the most popular and most recognized pacu fish.

- Piranhas belong to the genus Pygocentrus and are part of the family Serrasalmidae. Common species include P. nattereri (red-bellied piranha), P. cariba (black piranha), and P. piraya (piraya piranha).

Physical Characteristics:

Pacu: Pacus generally have a more rounded body shape with a laterally compressed body. They often have straighter, less triangular teeth.

Piranha: Piranhas typically have a more streamlined and compact body shape. Their teeth are more triangular, razor-sharp, and interlocking.


Pacu: Pacus are generally larger than piranhas and can grow to substantial sizes, sometimes exceeding three feet.

Piranha: Piranhas are smaller, usually ranging from about 6 to 24 inches in length.


Pacu: Pacus are herbivores and omnivores, primarily feeding on fruits, nuts, and vegetation. They are generally considered less aggressive than piranhas.

Piranha: Piranhas are carnivores and known for their aggressive behavior, often hunting in packs. They primarily feed on fish and occasionally other small animals.


Pacu: Pacus are found in various freshwater habitats, including rivers, lakes, and flooded areas with abundant vegetation.

Piranha: Piranhas are also found in freshwater habitats in South America but are more commonly associated with fast-flowing rivers and streams.

Teeth Structure:

Pacu: Pacus have flatter, more human-like teeth adapted for crushing and grinding plant matter.

Piranha: Piranhas have sharper, serrated teeth designed for tearing and slicing through flesh.


Pacu: Pacus are generally considered less aggressive, making them more suitable for community aquariums.

Piranha: Piranhas can be highly aggressive, especially during feeding times or when they feel threatened.

In summary, while pacus and piranhas share similarities due to their common ancestry, their distinct physical features, behaviors, and dietary preferences make them two different species with unique characteristics. Understanding these differences is crucial for proper care and management in captivity.