Arapaima (Pirarucu)

Geographic Origin and Biotope: The giant of the Amazon and Essequibo basin. Inhabits flooded forests (varzea), rivers and marginal lakes. Thrives in hypoxic (oxygen-poor) waters of calm rivers, coming up to breathe air.

Taxonomy and Morphology: Arapaima / Pirarucu (Arapaima gigas). One of the largest freshwater fish in the world (exceeds 3 meters / 10 feet). It is a living fossil (Arapaimidae) equipped with immense armored scales and a massive mouth bristling with crushing teeth.

Social Behavior: Supreme and undisputed hunter. Breathes atmospheric air through a modified swim bladder similar to a lung, emerging noisily (gulp) every 10-15 minutes. Relatively tolerant towards immense fish that do not fit in its mouth.

Coloration and Sexual Dimorphism: Bronze-gray as juveniles, upon maturing they develop spectacular fiery red scales (Arapaima = "Red Fish" in Tupi) on the rear half of the body. There is no evident sexual dimorphism outside the breeding season.

Aquarium Setup: ABSOLUTELY UNSUITABLE FOR DOMESTIC AQUARIUM KEEPING. Exclusively intended for zoos, public mega-aquariums or huge heated tropical ponds of tens of thousands of liters/gallons. Needs reinforced anti-jump nets.

Diet and Feeding: Apocalyptic carnivorous predator. Feeds on whole fish, frogs, crustaceans and birds that fall into the water. In captivity it is fed with tilapia fillets, floating pellets for giant Koi and frogs.

Water Quality: Extremely resilient, especially to oxygen scarcity, but its impressive organic load (feces) will quickly turn any tank not equipped with gigantic industrial filters into a sewer.

Compatibility and Tankmates: Everything under 40-50 cm (16-20 inches) is instant food. Cohabits in public mega-systems with large Pacu (Colossoma), Phractocephalus hemioliopterus (Redtail Catfish) and giant freshwater Stingrays (Potamotrygon).

Aquarium Reproduction: Unthinkable in home aquariums. Reproduces by digging enormous holes in the sandy bottoms during the dry season. The male is a model parent who guides the fry in a group, keeping them close to his dark head.

Risks and Diseases: Endangered species protected by CITES. Its reckless sale as a 10 cm (4 inch) puppy ("cute monster") invariably causes the death of the fish in cramped tanks or the collapse of home glass due to impacts as an adult.