Arapaima | Arapaima gigas
Others / Osteoglossidae / Arapaima
Profile: Pirarucu, Arapaima
Pirarucu, Arapaima 
Synonyms: Sudis gigas, S. piracuru, Vastres agassizii, V. curvieri
Physical description: The body is covered with large, thick scales. The tail is small and round and the body is elongated. It has a large, wide mouth that faces upward. Its head to midsection is dark brown to black with blue highlights. From the midsection to the tip of the tail, the scale are dark, but edged with red. The red color becomes more dominant towards the tail.
Size/Length: To 16' (4.9 m) in nature, although usually not more than 5' (1.5 m) in captivity.
Similar species: None
Habitat: Inhabits floodplain pools with little oxygen in South America; Amazon and Orinoco rivers.
Aquarium: A tank measuring 96" (244 cm) with a capacity exceeding 200 gallons (758 L) is suitable for fish measuring up to 30" (76 cm). Larger fish should be transferred to a larger tank or to a public aquarium. Large open swimming areas should be provided along with areas of plating with large plants. A tight fitting cover is required as this large species can jump. A powerful filtration system to remove waste is needed, although it should create little current. A cover of floating plants to diffuse the lighting is suggested.
Water chemistry: pH 5.8-7.2 (6.7), 2-12 dH (8), 75-86°F (24-30°C)
Social behavior: Only combine with other large fish of lower swimming levels. A highly predatory fish that acts aggressively towards similar species.
Suggested companions: Astronotus, Anostomus, Cichlasomines, Loricarids, Colossoma, Leporinus, Mylossoma, Pseudoplatystoma, Serrasalmus, Sorubim
FOOD: Live; primarily fish, also large crustaceans, frogs; chopped meat; possibly pellets once acclimated.
Sexual differences: Males are redder during the spawning season.
Breeding techniques: Breeding is nearly impossible in an aquarium. Goulding documented the Arapaima's reproductive behavior in nature, at the start of the flood season, the Arapaima prepares a nest in shallow areas of stagnant water pools. Both the male and the female use their snout, mouth, and fins to dig a pit in the river bed. This pit can measure up to 20" (50 cm) in diameter and 8" (20 cm) deep. The female deposits up to 50,000 eggs in this nest, after which the male fertilizes them. The parents drive off predators by loud tail-slaps that they produce when they surface to breathe. The male protects the eggs while the female guards the general territory. The eggs hatch after 4-5 days, and the 1/2" (13 mm) larvae are free-swimming 6-7 days after. The young have functioning gills, but still surface every 4-6 minutes (Goulding 133). The young match the dark color of the male's head, and camouflage well while swimming near him." Once the young are old enough to fend for themselves, after about three months, they are abandoned. Few eggs and fry survive because of heavy prederation.
Breeding potential: 10. Breeding is not possible in the home aquarium.
Farming the world's largest freshwater fish - an alternative to deforestation
Difficulty of care: 10. This hardy species grows too large to be kept in a home aquarium. This species is best left in the wild where it belongs.