Should I buy it?
Oscar
Astronotus ocellatus
Also known as: velvet cichlid, Velvet cichlid
Fishori provides conservative planning guidance, not guarantees.
Based on multiple reputable aquarium care sources with strong agreement. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
Massive personality, even more massive tank requirement. A single oscar realistically needs 300L+ and produces enough waste to push your filter to its limit.
Best for
Single-species or oscar-pair setups with 300L+ and serious filtration. People who genuinely want a 'wet pet'.
Avoid if
You have anything under 250L; want plants, small fish, or a low-maintenance setup.
Top things that go wrong
- Grows large or needs a very big footprint. Oscar is often sold at sizes that hide adult length (~35cm on file) and a published minimum near **300L**. Shop tanks are not adult housing.
- Mouth gap vs tiny tank mates. Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
- Shrimp & snails. Shrimp: not safe. The fish will eat adult shrimp, shrimp fry, or both, depending on the size of the shrimp.
Common mistakeTwo oscars in 200L. Adult turning radius and nitrates scale faster than a weekly water change.
What most shops don't tell you
- 1.Predation risk scales with gape, night feeding, and crowding. 'they grew up together' is a schedule, not a law.
- 2.Two oscars in 200L. Adult turning radius and nitrates outpace a weekly water change habit.
- 3.Housing with small tetras. 'They grew up together' ends when one fits in a mouth.
- 4.Oscars produce the bioload of a small dog and need a 300L+ tank with serious filtration. They eat anything under 15 cm. Single-species or large-cichlid setups only.
About this species
Oscars are large South American cichlids that learn faces, beg for food at the glass, and will eat any fish that fits in their mouth. The adult is 30 to 35 cm.
- Green Terror300L min · same group, comparable tank size
- Severum250L min · same group, comparable tank size
- African Cichlid200L min · same fish family
- Convict cichlid200L min · same fish family
- Discus200L min · same fish family
- Firemouth Cichlid200L min · same fish family
- Jack Dempsey200L min · same fish family
- Keyhole cichlid200L min · same fish family
- African Cichlidalso intermediate aggressive, similar tank size
- Green Terroralso intermediate aggressive, similar tank size
- Jack Dempseyalso intermediate aggressive, similar tank size
- Common Pleco tank mateslists this fish as a safe and recommended mate
- Green Terror tank mateslists this fish as a safe and recommended mate
- Jack Dempsey tank mateslists this fish as a safe and recommended mate
- Jaguar cichlid tank mateslists this fish as a safe and recommended mate
- Red-tailed catfish tank mateslists this fish as a safe and recommended mate
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease29
- Peacefulness0
- Community fit0
- Small-tank fit66
- Hardiness57
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Avoid “one of everything” baskets — Oscar belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Tank mate intelligence
Best alone or with similar-size robust cichlids (severum, jack dempsey) in 500L+ setups. Anything under 15cm becomes a snack.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Oscar + Jack Dempsey
- Try Jack Dempsey — open the pair check.
- Try Green Terror — open the pair check.
- Try Common Pleco — open the pair check.
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Aggressive and intelligent. They rearrange decor, dig substrate, and recognise the human at the glass. But they do not tolerate community fish at adult size.
Stress / aggression triggers on file
- Crowding and limited territory
- Similar-looking fish in the same tank
- Spawning, for any breeding pair
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Predation risk toward smaller tank mates. The figure that matters is the adult mouth size against the adult prey length, not the juvenile sizes in the shop.
Territory: Holds territory on substrate, in caves, or at the surface film. Break the line of sight with hardscape, and avoid placing the tank where the fish can see its own reflection.
Planted tanks: caution — pick tougher plants
In the glass: typical and warning signs
- Moderate pacing — not hyperactive, not motionless.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Chasing one individual repeatedly, torn fins on tank mates, or food theft every feed.
- Corner guarding, flaring, or body-blocking — territory is normal until it becomes relentless.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
variable
Diet
carnivore
Small invertebrates, frozen bloodworm or daphnia, and protein-rich prepared foods. Rotate the menu and feed by appetite rather than by clock.
Shrimp & snails
Shrimp: not safe. The fish will eat adult shrimp, shrimp fry, or both, depending on the size of the shrimp.
Kept singly or as a paired setup. Check the species profile before doubling up in one tank.
Breeding behaviour depends on the species. Research before you buy a mixed-sex group of this fish.
- Hold 23 to 28 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 6 to 8 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Footprint: short wide tanks and tall narrow tanks fish differently for the same volume. Match the tank shape to the swim pattern, not just the litre count.
- Tank volume meets or exceeds 300L published minimum for adults.
- Heater can hold 23–28°C without cooking cooler-water tank mates.
- No tank mates small enough to fit the adult mouth gap for this species.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 300L minimum tank needs a filter rated for at least 1200L/hr turnover and a heater to hold 23–28°C reliably.
Profile status: verified · Evidence tier: high · 4 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Astronotus ocellatus
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Astronotus ocellatus
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Astronotus ocellatus
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
- Wikipedia. Astronotus ocellatus (oscar)
Encyclopaedia overview; use specialist aquarium sources for your stock's real temperature/pH/footprint needs.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.