Red-bellied Pacu (Piaractus brachypomus)

Common Name:

Red-bellied Pacu.

Other Names:

Tambaqui, Pirapitinga.

Scientific Name:

Piaractus brachypomus.

Family:

Characidae or Serrasalmidae.

Distribution:

The basins of the Amazon and Orinoco Rivers.

Size:

FishBase puts the maximum length at nearly 3 feet (88.0 cm). Two feet and longer are very common lengths attained in captivity.

Diet:

They eat some insects in the wild but really love vegetation, especially that which is in a state of decay. They tend to do best in tanks where they are kept as vegetarians with a little bit of carnivore-based prepared food or small live foods fed occasionally. Romaine lettuce, all sorts of fruits and clippings from aquarium plants are readily taken. They can also crack nuts easily and may be given those on occasion.

Water Temperature:

73 to 82 degrees Fahrenheit (23-28 degrees Celsius).

Water Chemistry:

Moderately hard water is appreciated (dH ~ 15).

pH:

5-7.

Life Span:

28 years max. Reported by FishBase (it is likely that they live longer as many captive Pacus have been reported to have reached their silver birthday).

Sexing:

The males, with their pointed dorsal and intense red coloration, become sexually mature at age three, while their female counterparts must wait until age four to come into season.

Description:

These are tall fish which give the appearance of a Red-bellied Piranha (Pygocentrus nattereri but they tend to be somewhat plumper despite the fact that the two are often confused. The most significant morphological difference between the two is the the level of protrusion of the jaw (much smaller in pacus than in piranhas). This helps to illustrate the largely vegetarian nature of the pacu and the largely carnivorous nature of the piranha.

They are either grey or silvery fish with red bellies and the pacu has red lower body fins as well. The tambaqui also grows to a size which Pygo. nattereri can never hope to achieve.

The genus to which the tambaqui formerly belonged, Colossoma was, at the time, the only genus of fish in which true molars are present. All genera which sprang from Colossoma are now among that still-somewhat-small assortment.

Though they aren't to be feared as much as piranhas, tambaquis have formidable teeth (see pic 4 or click here ) which will be used on careless keepers that anger or scare them. The name Serrasalmidae means "Salmons with a Saw" (David Schleser, "Piranhas: A Complete Owners' Manual"), and this accurately describes the dentition of the Pacus.

Behaviour:

Pacus do best when kept in shoals when they are young but have been found to live solitarily in the wild as they age.

They are known to dispatch glass-encased heaters with some regularity and should thus be either shielded from them or kept warm via titanium heaters.

Breeding:

Not accomplished in aquaria, but the Houston Zoo reports that females lay smooth, spherical eggs, which are subsequently fertilized by their male counterparts. The pair then abandons the eggs. At some point, hatching occurs, but the length of the incubation period is unknown.

Natural Conditions:

The young are found solely in shallow black water, but the adults will be found throughout the Amazon-Orinoco, especially the flooded forests during the rainy season. (Where else would they get their rotting fruit and tree nuts?).

Minimum recommended tank size:

300 gallons with at least additional 200 gallons for every other Pacu.

Miscellaneous:

This is the most common Pacu and, as such, is known simply as "Pacu" in some regions of North America.

The Houston Zoo's webpage provided quite a bit of information on this fish.

Photo Credit:

Photos supplied courtesy and ^© Aquamojo