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No federal permit to keepOscar
Astronotus ocellatus
Fishes › Cichlids (Cichliformes) › Cichlidae (Cichlids)
The oscar (Astronotus ocellatus) is a species of fish from the cichlid family known under a variety of common names, including Tiger Oscar, Velvet Cichlid, and Marble Cichlid.
Care at a glance
Species-specific values
Values researched for this exact species. Where they differ from the group guide below, follow these. Air, surface and water temperatures are listed separately, and each source is kept as published rather than averaged.
| Water temperature | 68–82 °F (20–28 °C) Seriously Fish aquarium recommendation; not a wild collection measurement. | 269 |
| Water pH | 6–7.5 pH Seriously Fish aquarium recommendation; not a wild collection measurement. | 269 |
| Water general hardness | 5–20 dGH Seriously Fish aquarium recommendation; not a wild collection measurement. | 269 |
| Maximum standard length | 350 mm SL Source maximum; not total length or a guaranteed adult size. | 269 |
| Minimum tank base | length: 150 cm; width: 60 cm One adult; pairs and groups require more room. | 269 |
| Captive lifespan | 10–20 years Profile estimate, not a guarantee. | 269 |
| Diet | Omnivore with a preference for animal foods; quality cichlid pellets plus varied suitable live or frozen foods. Avoid mammal/bird meat and disease-prone feeder fish. | 269 |
Species-specific aquarium care
- Tank: At least 48 in long and 18 in front to back for one adult (adults commonly reach about 9.4 in / 24 cm; the largest recorded was 18.0 in).
- Water: Freshwater.
- Temperature: 72–77°F (range recorded for this species).
- pH: 6–8.
- Hardness: 5–19 dGH.
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Diet: Eats a varied diet: mix quality prepared foods with frozen and live foods. FishBase classes it as a omnivore.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 59 × 24 in (roughly 143 US gallons); space needed is rated “very large tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 68–82 °F, pH 6–7.5, 5–20 dGH.
- Behaviour: in a pair; not a community fish.
- Difficulty: Moderate (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “Unsuitable for the carefully-aquascaped aquarium since it has a tendency to dig into the substrate but otherwise relatively unfussy.”
- Diet: “This species is a generalised omnivore, feeding on a range of items including smaller fish, insects, crustaceans, zooplankton and various types of both terrestrial and aquatic vegetation in the wild, although meatier foods appear to be the preferred option…”
- Tankmates: “Although not especially aggressive for a cichlid of this size this species' predatory nature dictates that it should not be combined with much smaller fishes.”
- Breeding: “This species is a substrate-spawner developing extended pair bonds.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Oscars, peacock bass, pike cichlids and eartheaters
Applies to most species in this group. Habitat: Large South American rivers. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- For one adult Astronotus ocellatus, plan at least a 150 × 60 cm base according to Seriously Fish; pairs and groups need more space. Use separate adult plans for Cichla and each eartheater species.
- Soft sand for eartheaters (Geophagus, Satanoperca), which sift substrate through their gills.
Climate & lighting
Starting point only: The blanket warm-water interval excludes the subtropical seasonal requirements of G. balzanii; use overrides. Check the species-specific values for this animal where shown.
| Water | 77–84°F |
Diet
- Astronotus ocellatus is an omnivore with a preference for animal foods; offer quality pellets and varied suitable foods rather than feeder-fish dependence. Cichla and substrate-sifting eartheaters require separate feeding plans.
Health watch
- Hole-in-the-head disease and lateral line erosion in poor water; eartheaters suffer on sharp gravel.
Understanding the animal
About this animal
About this animal
In tropical South America, where the species naturally resides, A. ocellatus specimens are often found for sale as a food fish in the local markets. The fish has been introduced to other areas, including India, China, Australia, and the United States.
Quoted from the Wikipedia article “Oscar (fish)” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater, in rivers and streams, lakes. Uses both the bottom and open water. Preferably inhabits quiet shallow waters in mud-bottomed and sand-bottomed canals and ponds. |
| Water it lives in | Freshwater, 72–77 °F (22–25 °C), pH 6–8, hardness 5–19 dH. |
| Climate | Tropical climate. |
| Behavior to plan for | Breeding: clutch tenders, biparental parental care. |
What this means for care
- Keep water within its wild range, 72–77 °F.
- Parents guard eggs or young, so expect territorial behavior when breeding.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 90°F (up to 94°F in the hottest sampled areas) |
| Cool-season lows | about 70°F (down to 64°F in the coldest sampled areas) |
| Average temperature | 78–81°F across sampled records |
| Relative humidity | 78–84% on average (driest month about 78%) |
| Rainfall | about 2372 mm a year |
Measured at 195 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | The oscar (Astronotus ocellatus) is a species of fish from the cichlid family known under a variety of common names, including Tiger Oscar, Velvet Cichlid, and Marble Cichlid. In tropical South America, where the species naturally resides, A. ocellatus specimens are often found for sale as a food fish in the local markets. The fish has been introduced to other areas, including India, China, Australia, and the United States. It is considered a popular aquarium fish in Europe and the U.S. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Behavior | Oscars will often lay claim to an area of the aquarium and will be very aggressive towards other fish encroaching on their newly established territory inside the aquarium or lake. The size of the territory varies depending on the size and aggressiveness of the fish, and its surroundings. Once the oscar establishes a territory, it will vigorously defend it by chasing away other fish. — Wikipedia (community-edited) |
| Reproduction | In captivity, both male and female clean a suitable spawning site - often a flat rock, or branches, or in a circular nest excavated in shallow water. Eggs (usually numbering in the thousands, ) are deposited and are guarded by both parents. Egg hatch in 3 or 4 days and parent move the fry to a shallow pit in the sand where they remain for 6 or 7 days. — FishBase |
| Appearance and size | Maximum length 45.7 cm tl male/unsexed; maximum published weight 1.6 kg. — FishBase |
| Biology | Preferably inhabits quiet shallow waters in mud-bottomed and sand-bottomed canals and ponds. Feeds on small fish, crayfish, worms and insect larvae. Quite popular with aquarists but not for aquaculturists because of its slow growth. — FishBase |
| History and naming | The species was originally described by Louis Agassiz in 1831 as Lobotes ocellatus, as he mistakenly believed the species was marine; later work assigned the species to the genus Astronotus. The species also has a number of junior synonyms: Acara compressus, Acara hyposticta, Astronotus ocellatus zebra, and Astronotus orbiculatus. — Wikipedia (community-edited) |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Typical adult weight
Average adult body mass in each database (FishBase gives the maximum recorded weight).
Adult length
Common length to maximum recorded length. Measured as total length. Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Minimum tank footprint
Seriously Fish recommends a tank base of at least 59 × 24 in (about 143 US gallons).
Veterinary & husbandry research
Veterinary & husbandry research
- Evaluation of the anesthetic efficacy of alfaxalone in oscar fish (Astronotus ocellatus) Bugman AM et al., American journal of veterinary research 2016
- Social isolation and aggressiveness in the Amazonian juvenile fish Astronotus ocellatus Gonçalves-de-Freitas E et al., Brazilian journal of biology = Revista brasleira de biologia 2006
- Distinct skin morphological and transcriptomic profiles between wild and albino Oscar Astronotus ocellatus Wang Q et al., Comparative biochemistry and physiology. Part D, Genomics & proteomics 2022
- Infectious spleen and kidney necrosis virus-associated large-scale mortality in farmed giant gourami, Osphronemus goramy, in India Swaminathan TR et al., Journal of fish diseases 2021
Peer-reviewed papers that mention this species alongside captivity, zoos, veterinary care or aquaculture. Some cover several species or mention it only in passing, so check the abstract. See all 12 on PubMed → 170
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Merck Veterinary Manual: Management of aquarium fish Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Merck Veterinary Manual: Types and features of aquatic systems Zoo, university or veterinaryThe Merck Veterinary Manual: a standard veterinary reference written and reviewed by veterinary specialists.
- Seriously Fish: Gymnogeophagus balzanii Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish — Astronotus ocellatus Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- PubMed (U.S. National Library of Medicine) Peer-reviewed researchIndex of peer-reviewed veterinary, zoo and husbandry research.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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