A highly intelligent, large, and personable South American cichlid often described as a 'water dog'. They are notoriously messy eaters, heavy waste producers, and will enthusiastically rearrange tank decor and uproot plants. Any fish small enough to fit in their mouth will be eaten. They require excellent filtration and strict water maintenance.
At a Glance
Tank Requirements
Water Parameters
Temperament & Compatibility
Available Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard Adult
The full-grown adult Oscar. Due to their extreme bioload and size, they require a 75+ gallon tank for a single specimen and heavy filtration.
Differs in 1 trait from base species
Also known as: Tiger, Red, Albino, Adult Oscar
Juvenile (Grow-out)
Young Oscars commonly sold at 5-10cm. They grow incredibly fast (up to an inch a month) and will quickly outgrow a starter tank. Must be upgraded to a 280L+ tank within a few months to prevent stunting.
Differs in 5 traits from base species
Also known as: Baby Oscar, Small Oscar, Juvenile
Veiltail / Long Finned
A selectively bred morph with long, flowing fins. They require lower flow to prevent fin damage and exhaustion, and should not be kept with fin-nipping tank mates.
Differs in 2 traits from base species
Also known as: Longfin Oscar, Veiltail Oscar
Oscar Care Summary
The Oscar, scientifically known as Astronotus ocellatus, belongs to the Cichlids - South American family group. Adults reach a maximum size of approximately 30 cm and have a compressed body shape with a fast growth rate. Classified as aggressive, this species primarily occupies the mid-level and bottom zones of the aquarium and produces a extreme level of biological waste.
To thrive, the Oscar requires a freshwater only aquarium with a minimum volume of 280 litres and a tank length of at least 120 cm. Water temperature should be maintained between 23°C and 27°C, with a pH range of 6–7.5 and a general hardness of 5–15 dGH. A moderate water flow is preferred. To replicate their natural habitat, the tank should include sand (sifters), smooth gravel (sensitive barbels), and driftwood (digestion/hiding).
Oscar can be kept singly or in a group, making them flexible additions to most setups. Keepers should be aware that this species will prey on fish small enough to fit in its mouth, will defend a territory within the tank, and may uproot or eat live plants. This species is available in 3 varieties: Standard Adult, Juvenile (Grow-out), and Veiltail / Long Finned. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Similar Species
Freshwater Angelfish
Pterophyllum scalare
The most iconic South American Cichlid, known for its distinct arrowhead shape and majestic fins. While domestic strains are hardy, they remain cichlids: they are semi-aggressive predators that will eat any fish small enough to fit in their mouths (like Neon Tetras). They form loose shoals as juveniles but pair off and become territorial as they mature. Height is more important than length for this species.
Jack Dempsey
Rocio octofasciata
A robust, highly territorial Central American cichlid named after the aggressive 1920s boxer, William 'Jack' Dempsey. They exhibit beautiful iridescent blue, green, and gold spangling over a dark background. As aggressive diggers and plant destroyers, they require a tank with sturdy decor. They are best kept as a single wet pet or in a large tank with other similarly sized, robust Central American cichlids.
African Jewel Cichlid
Hemichromis bimaculatus
A strikingly beautiful but notoriously aggressive West African riverine cichlid. Unlike the alkaline-loving Rift Lake cichlids (e.g., Mbuna), Jewel Cichlids prefer neutral, softer water parameters. They are renowned for their brilliant red breeding dress and iridescent blue spots, but also for their extreme territoriality, especially when forming pairs and spawning. They are avid diggers and will uproot most plants.
Discus
Symphysodon aequifasciatus
Known as the 'King of the Aquarium', Discus are stunning, heavily laterally-compressed cichlids. They are famous for their demanding husbandry, requiring high temperatures (28-32°C / 82-90°F), pristine water quality, and specialized diets. They are schooling fish that establish a strict pecking order and must be kept in groups to prevent intense bullying of a single weaker fish.
Flowerhorn Cichlid
Cichlasoma sp. hybrid
A man-made hybrid cichlid famous for its vibrant colors, extreme interactive personality, and the large nuchal hump (kok) on its head. They are incredibly aggressive 'wet pets' that will attack hands, tank mates, and equipment. They have a massive bioload, dig constantly, and must almost always be kept completely alone.
Amano Shrimp
Caridina multidentata
A highly popular, industrious freshwater shrimp renowned for its unmatched algae-eating abilities. Popularized by aquascaper Takashi Amano, they are significantly larger and hardier than most dwarf shrimp (like Cherry Shrimp). They are notorious food-thieves during feeding time and excellent escape artists, requiring a tight-fitting lid. Their larvae require saltwater to develop, so they will not overpopulate in a freshwater aquarium.