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Red Bellied Pacu (Colossoma macropomum)

Photo of: Red Bellied Pacu (Colossoma macropomum)

Scientific Name(s): Colossoma macropomum


Common Name(s): Red Bellied Pacu, Red Belly Pacu, Blackfin Pacu, Pacu, Tambaqui


Family: Characidae


Species Type: Characins (Tetras)


Maximum Size: 42 inches


Life Span: 15 years


Natural Habitat: South American rivers and lakes


Minimum Tank Size: 1200 gallons


Tank Region: All over


Possible Tank Mates: This fish would do well with most fish that have similar water requirements. Unfortunately, due to the size of this fish it is not suitable for long term home aquarium use.



The Red Bellied Pacu is a cousin of the pirannah. Unlike the pirannah, the Pacu prefers vegetation to live foods. The Red Bellied Pacu grows to enormous sizes (42+ inches) and is not suitable for home aquariums.


Read this story about the enormous tank size requirements for Pacus

I bought two red belly pacus back in 1993, when they were only the size of a half dollar coin. Not doing any research on these two fish, I bought them because I enjoyed their manner in appearance, the way they fed, and their "unaggressiveness"; however, as they slowly grew in size, despite their small size, all of my small connunity fish became their dinner. Years later, (around Sept. 1999) reluctantly, I gave them up. They were still surviving in a 200 liter tank, with crystal clear water flowing endlessly, as they stayed by the bottom of the tank, moving slowly about, and only during feeding time did they briskly move their now 50 cm long, close to 6 kg bodies about. These two beautiful fish were like family members; the maintenance was grueling, but more importantly, I loved them, and could no longer subject them to such confining living space. Living only some 56 km southeast from San Francisco's famous Steinhart Aquarium, I finally got a commitment from the staff that they would keep my fish, instead of "utilizing them as fish feed". My pacus were initially placed in a 2000 liter holding/quarantine tank, making sure they did not harbour any parasites or diseases that could infect other members of the amazon-type setting they would eventually be placed. Finally, my two pacus were placed in a 50,000 liter amazon type pool, along with several larger pacus, caymen, large tortoises, eels, and other amazon type fish. On several occasions I visited them, and they grew even larger (twice their size). Interestingly, I was always able to recognize them (they were lighter in colour) and believe it, or not, I would gently tap on the glass, and "call" out to them: "Hey guys, how are you doing?", and as they had done hundreds of times when I had them at home with me, they would swim where I was, and stay by me, as if saying: "We are fine, now are you going to be feeding us?"


Temperature Range: 70°F - 82°F



pH Range: 5.2 - 7.8

pH 5.0
pH 6.0
pH 7.0
pH 8.0
pH 9.0


Hardness Range: 8° - 18°



Breeding Information: These should not be bred as they are not suitable for home aquariums.


Sexing Information: Males tend to have an underbelly that is more vividly red. The anal and dorsal fins also tend to be more pointed for males.


Diet: Omnivorous but tends to prefer vegetable matter. These guys will devour most aquarium pkants but seem to do well with java moss.


Temperament: Generally peaceful and rather skittish. This skittish behaviour is particularly dangerous when the fish gets large and swims into the side of a glass aquarium.


Common Diseases: None specific to species but prone to injury in aquariums due to running into glass.


This Red Bellied Pacu profile has been viewed 5042 times.


Characins (Tetras)


Keith Pardee

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