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The Astronotus ocellatus, also called the Smooth Red Oscar, is a color variety of the well-known South American cichlid Astronotus ocellatus. Its sturdy body, apparent intelligence, and ability to recognize its keeper make it highly sought after. The Smooth Red form is distinguished by a more uniform red coloration and a less pronounced pattern than tiger Oscars. Despite its popularity, it remains a large fish requiring a spacious aquarium, powerful filtration, and carefully selected tankmates. It is considered very common in the aquarium trade, but its care is best suited to experienced aquarists.

General description of the species

The Astronotus ocellatus is a large freshwater cichlid belonging to the family Cichlidae and the subfamily Cichlinae. The species is known for its rapid growth, hardiness, and expressive behavior. It may move decorations, dig through the substrate, and splash water when stimulated or fed. The Smooth Red form is a selectively bred variety valued for its red-orange coloration and more uniform appearance. Like other Oscars, it becomes territorial, especially during spawning, and may swallow any fish small enough to fit in its mouth. An adult requires an aquarium of several hundred liters, with particular attention given to water quality and sturdy décor.

Geographic origin and biotope

Native to South America, Astronotus ocellatus mainly occurs in the basins of the Amazon, Orinoco, and Guianas. Countries referenced: Brazil, Peru, Colombia, Venezuela, Guyana, and Suriname. It inhabits slow to moderately flowing waters, including floodplain lakes, backwaters, forest creeks, and quiet areas of large rivers. These environments generally have warm, soft to moderately mineralized water that may be stained by tannins. The bottom is commonly made up of sand, mud, and plant debris, with roots, submerged branches, and natural shelters. Vegetation varies with water levels, but wooded banks and flooded forests provide important cover.

Precise location and local name

Within its natural range, Astronotus ocellatus is associated with several major South American drainage systems, including the Amazon, Orinoco, and Guianan rivers. Populations may live in varied habitats, from flooded plains to forest lagoons connected to rivers. In Brazil, the species is commonly called apaiari or acará-açu, names used in different regional contexts. The name Oscar is mainly used in the international aquarium trade. The Smooth Red form does not represent a distinct geographic population; it is a captive-bred line selected for its red pattern and reduced dark markings.

Appearance and physical characteristics

The Astronotus ocellatus has an oval, laterally compressed body, a massive head, and a broad mouth suited to capturing prey. The dorsal and anal fins are elongated, giving the fish an imposing appearance. Like many Oscars, it may have an eyespot near the base of the caudal fin, especially in non-selected specimens. The Smooth Red variety mainly displays red, orange, or copper coloration along the flanks, with intensity varying according to the strain, age, and condition of the fish. The eyes are often reddish or orange. Its size, strength, and ability to rearrange the aquarium décor are major characteristics to anticipate in captivity.

General diet

In the wild, Astronotus ocellatus is an opportunistic predator that consumes fish, crustaceans, aquatic insects, and other small organisms. In an aquarium, its diet should be based on high-quality pellets for large cichlids, supplemented with frozen foods such as shrimp, krill, or worms. Vegetables may be offered occasionally, but they should not form the foundation of the diet. Live feeder fish are unnecessary and may introduce parasites or create an unbalanced diet. It is preferable to offer small portions suited to the fish’s size rather than one large meal. An overly rich or excessive diet promotes obesity and quickly compromises water quality.

Essential data

• Original river: Amazon, Orinoco, and Guianas drainage basins
• Local name: Apaiari, acará-açu; Oscar in the aquarium trade
• Origin of the scientific name: Astronotus was formed from Greek terms associated with star and back; ocellatus refers to eyespot-like markings
• Etymology of the full name: Astronotus roughly means “starry back”; ocellatus means “bearing an eyespot” or “marked like an eye”
• Common/vernacular names: Oscar, Tiger Oscar, Smooth Red Oscar, apaiari, acará-açu
• Family: Cichlidae
• Subfamily: Cichlinae
• Name pronunciation: ass-tro-NO-tuss oh-sell-AH-tuss
• Discovery: Louis Agassiz, 1831
• Maximum adult size: About 45 cm
• Water temperature and pH: 23 to 28 °C; pH 6.0 to 7.5
• Waterway appearance and surrounding vegetation: Slow waters, backwaters, lagoons, and floodplains bordered by forest, roots, and submerged vegetation
• Typical tankmates: Colossoma macropomum, Mylossoma duriventre, Potamorhina altamazonica, Prochilodus nigricans, Leporinus friderici, Curimata inornata
• Temperament and behavior: Intelligent, territorial, digging, and generally aggressive toward small fish
• Water depth: Quiet, shallow to moderately deep areas of floodplains and river margins
• Sexual dimorphism: Very difficult to determine outside spawning; the sexes are generally alike
• Bottom structure and flow: Sand, mud, plant debris, and branches; low to moderate current

In your aquarium

To succeed with Astronotus ocellatus, provide a large aquarium, a secure lid, and filtration capable of handling a heavy organic load. Use sturdy décor without fragile plants, since this cichlid likes to dig and move objects. Stable water, regular water changes, and measured feeding are essential. Avoid small tankmates and watch for dominance, especially when a pair forms. Its engaging personality should not obscure its needs as a large fish: space, filtration, and cautious compatibility are the keys to long-term success.