Arapaima gigas

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The Arapaima gigas, also known as paiche or pirarucu, is one of the largest freshwater fish in the world. Native to the Amazon Basin, it inhabits floodplains, várzea lakes and quiet sections of major rivers. Its massive body, thick scales and ability to breathe atmospheric air make it spectacular, but extremely demanding in terms of space. This profile concerns a wild-collected species. With a rarity rating of 3 — very rare, it is intended mainly for experienced aquarists with exceptional facilities.

General species description

Arapaima gigas is a giant predatory fish from the family Arapaimidae, adapted to warm Amazonian waters that may become oxygen-poor. It has a highly vascularized swim bladder that acts as an accessory respiratory organ, so it must regularly reach the surface to gulp air. This adaptation allows it to survive in stagnant waters and temporarily isolated habitats during the dry season. Its normal behavior is often calm, although it can accelerate powerfully when striking prey. In captivity, its growth, adult size and strength require extraordinary volume, powerful filtration and a securely fitted cover. It is not suitable for a standard home aquarium.

Geographic origin and biotope

In Peru, Arapaima gigas is associated with the Amazon Basin, particularly the floodplains of the Loreto region and areas connected with the Marañón, Ucayali and Amazon drainage systems. It inhabits várzea lakes, dead-end channels, quiet waterways and seasonally flooded forest. Water levels change substantially throughout the year. Water may be relatively clear, brownish or rich in organic matter, depending on river connections and flooded vegetation. Temperatures remain high year-round. Surrounding vegetation includes dense riparian forest, submerged roots, fallen branches and sometimes mats of floating plants. The specimens covered here are wild-collected, rather than identified as captive-bred stock.

Precise location and local name

In Peru, the species is strongly associated with Loreto, around the Amazon, Marañón and Ucayali networks, including their lakes and floodplains. The most common local name is paiche, also spelled paiche in English-language references. The name pirarucu is used mainly in Brazil, while the aquarium trade often uses arapaima. These names commonly refer to the same fish, although local usage varies among regions. In the wild, Arapaima gigas often remains in quiet areas with cover and easy access to the surface for air breathing. Its commercial rarity is rated very rare.

Appearance and physical characteristics

The body of Arapaima gigas is elongated, cylindrical and covered with large, heavily mineralized scales that can help resist bites from some predators. The head is broad and flattened, with an upturned mouth suited to taking prey near the surface. Overall coloration ranges from gray-green to dark brown on the front of the body, while the rear body and caudal fin may show reddish to copper tones, especially in adults. The dorsal and anal fins are positioned far back near the caudal fin, emphasizing the fish’s powerful profile. Obligatory atmospheric respiration is one of its defining features. The maximum reported size is approximately 450 cm, although individuals of that size are exceptional. A truly monumental installation is therefore required.

General diet

Arapaima gigas is an opportunistic predator that feeds mainly on fish, along with crustaceans and other available aquatic animals. It usually hunts close to the surface, where it can engulf prey with its large mouth. Young fish take proportionally smaller prey, while adults can consume comparatively large fish. In captivity, the diet should emphasize whole or suitable foods for large predators from safe sources, rather than feeder fish that may introduce parasites. Meals must be adjusted to the animal’s size and activity, since overfeeding can quickly degrade water quality. Stable, well-maintained water remains essential despite its ability to breathe air. Never rely on small tank mates: they will be regarded as potential prey.

Essential data

• Native river name: Marañón and Ucayali, in the Peruvian Amazon Basin
• Local name used: Paiche or paiche
• Origin of the scientific name: Arapaima is an Amazonian vernacular name; gigas comes from Greek and means giant
• Full-name etymology: Arapaima preserves a local name; gigas means “giant” and refers to the species’ exceptional size
• Common/vernacular names: Paiche, paiche, pirarucu, arapaima
• Family: Arapaimidae
• Subfamily: No commonly retained subfamily
• Name pronunciation: ar-uh-PIE-muh JIG-us
• Discovery: Heinrich Rudolf Schinz, 1822
• Maximum adult size: Approximately 450 cm
• Water temperature and pH: 24–30 °C; approximately pH 6.0–7.5
• Waterway appearance and surrounding vegetation: Várzea lakes, quiet channels and floodplains; dense riparian forest, roots, submerged branches and floating plants
• Typical tank mates: Astronotus ocellatus, Phractocephalus hemioliopterus, Osteoglossum bicirrhosum
• Temperament and behavior: Generally calm, opportunistic predator, powerful and capable of swallowing smaller fish
• Water depth: Quiet, shallow to moderately deep floodplain habitats; frequent access to the surface is essential
• Sexual dimorphism: External differences are subtle outside the breeding period; mature males may show stronger coloration
• Bottom structure and flow: Muddy or sandy-muddy bottom, woody debris and low-current to slow-flow areas

For aquarium success

Success with Arapaima gigas begins with a system capable of accommodating a fish far beyond normal aquarium dimensions. Provide oversized filtration, excellent water quality, open surface access for breathing and a firmly secured cover. Decorations must be sturdy while leaving broad swimming areas. Because this is a very rare, wild-collected animal, traceability, applicable permits and legal origin should be checked before any purchase. Tank mates must be selected carefully, since its mouth and growth rate make smaller fish vulnerable. For most hobbyists, observing the species in a specialized public facility remains the most responsible option.