Tambaqui (Black Pacu)

Geographic Origin and Biotope: Native to the Amazon and Orinoco basins. This colossus inhabits main rivers, floodplains and flooded forests, where it feeds on the fruits and seeds that fall from the trees above during the rainy season.

Taxonomy and Morphology: Tambaqui / Black Pacu (Colossoma macropomum). Often confused with the Piranha due to the discoid shape of the body. However, unlike the Piranha, the Tambaqui has flat human-like teeth (molars) used to crush very hard nuts and seeds.

Social Behavior: It is an extremely peaceful and tolerant fish, although it is very shy and easily frightened (a frightened 20 kg specimen can literally smash the aquarium glass by headbutting it). As a juvenile it lives in schools, as an adult it is more solitary.

Coloration and Sexual Dimorphism: Lead gray to uniform charcoal black coloration, sometimes with olive hues. Juveniles have a reddish abdomen and dark spots, which is why they are sold as "vegetarian piranhas". No obvious sexual dimorphism.

Aquarium Setup: NOT A HOME AQUARIUM FISH. Grows up to 1 meter (39 inches) and can weigh 30 kg (66 lbs). Requires mammoth tanks (minimum 3,000 liters / 800 gallons). No plants (it would eat them all), only huge roots anchored to the ground and industrial filtration.

Diet and Feeding: Omnivore (mainly frugivore). Literally devours buckets of food: whole apples, grapes, zucchini, nuts, giant koi pellets and crustaceans. It has an insatiable appetite and produces an impressive organic load.

Water Quality: Very resistant to chemical variations, but its size produces so much ammonia that the water quality collapses without huge pond filters and immense weekly water changes.

Compatibility and Tankmates: Peaceful with fish too large to be swallowed (e.g. giant Arowanas, huge Plecostomus or Redtail Catfish). It will inevitably swallow small and medium-sized fish that it mistakes for fruits.

Aquarium Reproduction: Impossible to breed in private aquariums due to size and migratory needs. It is artificially reproduced (with hormone injections) in aquaculture in South America for food purposes.

Risks and Diseases: The main risk is not for the fish (very hardy), but for the aquarist: buying cute 5 cm babies inevitably leads to having to get rid of them when they reach 40 cm in a few months. Risk of lethal head trauma if it gets scared and hits the glass.