Red-bellied piranha
A shoaling characin whose reputation is almost entirely wrong: it shoals for protection rather than to hunt, is nervous of movement outside the tank, and is a scavenger and fin-biter as much as a predator. Keeping it well means a large tank, a real group and no expectation of a display animal.
Quick profile
- Scientific name
- Pygocentrus nattereri
- Adult size
- 25–33 cm (9.8–13 in)
- Lifespan
- 10–20 years
- Temperature
- 24–28 °C (75–82 °F)
- pH
- 5.5–7.5
- Hardness
- 2–15 °dGH
- Minimum tank
- 600 L (159 US gal)
- Minimum length
- 180 cm
- Swimming zone
- Midwater
- Social
- Shoaling — at least 5
- Diet
- Carnivore
- Overall confidence
- moderate confidence
What keeping this species involves
A large tank, a group, and a fish that spends much of its life hiding from the room. It is a demanding animal to keep well and an easy one to keep badly.
Turbid slow rivers, floodplain lakes and flooded forest, in warm soft water with heavy cover.
Identity and names
- Common name
- Red-bellied piranha
- Scientific name
- Pygocentrus nattereri
- Family
- Serrasalmidae
- Order
- Characiformes
- Class
- Actinopterygii
- Also sold as
- Pygocentrus nattereri, Serrasalmus nattereri, red piranha, natterer's piranha
- Former or synonymous names
- Serrasalmus nattereri
Adult size and growth
25–33 cm (9.8–13 in)
Typical lifespan in an aquarium: 10–20 years. Almost every animal sold in a shop is a juvenile, so the tank has to suit the size in the first line rather than the size in the bag.
Shape, which is what the compatibility engine reads instead of length alone: disc — as deep as it is long with a moderate. Piranha take bites rather than whole fish, which the gape model cannot express. The predation traits carry the real risk for this species and the shape model deliberately does not inflate it.
Water and tank requirements
A shoal of thirty-centimetre fish that need to be able to spread out. Kept in a tank that forces proximity they turn on each other, which is the standard failure of this species in aquaria.
Temperature (°C)
Scale: 0 to 36 °C.
pH (pH)
Scale: 4 to 9.5 pH.
Hardness (°dGH)
Scale: 0 to 30 °dGH.
Why these ranges: A wide South American range across several basins, warm and soft to moderate. The species is tolerant within the band and reacts more to instability than to any particular value.
Where these figures come from
Habitat class
Lowland floodplain
Seasonally inundated flat country — várzea, chaco, swamp margin — where the water body changes size, depth and chemistry through the year.
The habitat's defining feature is change, so a single band describes it badly. Species from here are generally tolerant of a wide range and intolerant of nothing much — which makes them easy to keep and easy to keep wrongly.
- Conductivity
- 40–300 µS/cm
- Flow
- still
- Dissolved oxygen
- low
- Seasonality
- strong
These are figures for the KIND of water body, not measurements of this species. They are AquariumHQ’s summary of the general limnology and are given wide because the water is.
- TemperatureReasoned on this record
- This record states its own reason for this band. See the water section.
- pHReasoned on this record
- This record states its own reason for this band. See the water section.
- General hardnessReasoned on this record
- This record states its own reason for this band. See the water section.
| Requirement | Value | Notes |
|---|---|---|
| Temperature | 24–28 °C (75–82 °F) | Stability matters more than hitting an exact figure. |
| pH | 5.5–7.5 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 2–15 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 600 L (159 US gal) | A floor, not a recommendation. |
| Minimum footprint | 180 cm long × 60 cm deep | A shoal of thirty-centimetre fish that need to be able to spread out. Kept in a tank that forces proximity they turn on each other, which is the standard failure of this species in aquaria. |
| Water flow | moderate | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Heavy planting, wood and shaded areas, with open water in the middle. Cover reduces the skittishness that causes most of the damage. |
Behaviour
- Hangs in cover and startles at movement outside the glass, which is the opposite of the fearless animal the name implies.
- Produces audible barking and drumming sounds with the swim bladder, most often during disputes within the shoal.
Telling males from females
No reliable external difference. Breeding fish of both sexes darken considerably.
Feeding
Eats fish, invertebrates, fruit and carrion in the wild, and a substantial part of the adult diet is fins bitten from other fish. Live feeder fish are unnecessary and add disease risk.
- Diet type
- Carnivore
- Staples
- Whole frozen fish, Prawn, Mussel, Earthworm, Large sinking pellets
- Avoid
- Live feeder fish, Mammalian meat
Breeding
- Strategy
- Eggs laid in a cleared nest and guarded by both parents
- Difficulty
- challenging
- Parental care
- guarding
Tankmates and compatibility
Assessments are derived from stored traits by the compatibility engine, with the reasoning shown. A verdict is a statement about probability, not a guarantee — individual temperament can override it.
| Towards | Risk | What it means |
|---|---|---|
| Small fish | near-certain | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | near-certain | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | near-certain | Determines whether a shrimp colony can grow rather than merely persist. |
| Snails | moderate | Applies to snails you wanted as well as snails you did not. |
| Long or trailing fins | frequent | Fin damage is an entry point for secondary infection. |
| Plants | nibbles | Tough species such as Anubias and Java fern survive most grazers. |
Any pair in the catalogue can be assessed with the compatibility checker.
Welfare considerations
Points where the way this species is commonly sold or kept differs from what it actually needs.
- Restricted or prohibited in many jurisdictions, including several US states, parts of Australia and elsewhere. This is a species where the legal position has to be checked before acquisition rather than after.
- The bite is genuinely capable of injury and the fish should be moved in a rigid container. Injuries to keepers usually happen during tank maintenance rather than during feeding.
Problems to watch for
Most problems in a tank containing this species are general rather than species-specific. Start with the troubleshooting index and work from the observation rather than from a guess at the cause.
What AquariumHQ does not yet hold
Species-level disease susceptibility is modelled in the graph and is not yet populated. Health pages will not be published until each condition has veterinary sourcing, because health content written without evidence is the most harmful thing this product could publish. The gap is recorded in the coverage report.
Where it comes from
- Native range
- The Amazon, Orinoco, Paraguay and Paraná basins, and coastal rivers of north-east Brazil
- Habitat
- Turbid slow rivers, floodplain lakes and flooded forest, in warm soft water with heavy cover.
What the checklists say
29 distribution statements retrieved from GBIF checklists. Establishment means is reproduced from the source where it states one, and left unstated where it does not — a record of presence is not a record of origin.
| Status | Places | What this means |
|---|---|---|
| Native | 10 | A checklist states the species occurs here naturally. |
| Introduced | 14 | A checklist states the species arrived here with human help. That is not a statement that it is established, harmful or illegal. |
| Recorded as present, establishment means not stated | 5 | The source records the species as present and does not say whether it is native or introduced. AquariumHQ does not fill that in. |
Legal status and responsible practice
Restriction note
Possession, sale and import are prohibited or licensed in a considerable number of jurisdictions, including many US states, several Australian states and various European countries. The rules differ substantially between them and change; check the position that applies locally rather than relying on any general statement.
Never release aquarium life into the wild
Aquarium animals, plants, and aquarium water must never be released into ponds, rivers, canals, drains or the sea — not even in a country where the species is sold freely. Released fish and invertebrates establish populations that displace native species, and released plants and water carry pathogens, parasites and fragments capable of spreading without any animal at all. If you can no longer keep an animal, rehome it through an aquarium society, a retailer that accepts returns, or another keeper.
- Rehome through a local aquarium society, a specialist retailer or another keeper.
- Unwanted plants go in household waste or a hot compost heap, never in a watercourse or a garden pond.
- Never empty a bucket of tank water into a drain that discharges to open water.
- If an animal is beyond rehoming, ask an aquatic veterinarian about humane euthanasia rather than releasing it.
Legal status is recorded from the sources named and was correct on the verification date shown. Rules change, and sub-national rules often differ from national ones. Check the current position with the relevant authority before acquiring, selling or moving any animal or plant.
Evidence
Every stored value with the kind of support behind it and where to check it. Evidence type and confidence are separate axes: an editorial position held confidently and a measurement held tentatively are different things.
| Claim | Value | Evidence type | Confidence | Source |
|---|---|---|---|---|
| scientific name | Pygocentrus nattereri | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | The Amazon, Orinoco, Paraguay and Paraná basins, and coastal rivers of north-east Brazil | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 25–33 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 10–20 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 24–28 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 5.5–7.5 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 2–15 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 600 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 180 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 5 | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
Last reviewed 2026-08-10. Values labelled as an aquarium-literature consensus are AquariumHQ editorial positions rather than measurements — see how evidence is handled.
Why we say this
What each figure on this page rests on, and how far that is from being independently established.
Every figure on this page has a provenance. Open any claim to see what AquariumHQ holds for it, which sources say what, and what a claim of that kind actually needs. Different claims need different evidence: an accepted scientific name is settled by one authority, while a legal restriction needs a current primary instrument. A single source is often the right answer rather than a thin one.
scientific nameAquariumHQ's own position, externally checkableBased on a verified authoritative source.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: accepted scientific name and classification — 1 authoritative source in an appropriate context. Checked against gbif on 2026-08-29. One authoritative backbone is what this class requires.
What would improve this: Go and read a source. This is reachable and has not been reached.
native rangeAquariumHQ's own position, externally checkableBased on a verified authoritative source.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: where the species occurs — 1 authoritative source in an appropriate context. 29 distribution statements held from GBIF checklists — native in 10, introduced in 14 countries. Establishment means is reproduced from the source, never inferred from occurrence.
What would improve this: Go and read a source. This is reachable and has not been reached.
adult sizeOne sourceAquariumHQ's own position, derived from evidenced inputs.1 citation, 1 independent origin
A single source: usgs-nas.
- 32 cm — USGS Nonindigenous Aquatic Species database · Maximum recorded · Observed in the wild · checked 2026-08-29
What this kind of claim needs: size a well-kept specimen reaches — no external source is required, provided AquariumHQ shows its reasoning. A documented maximum is held and the catalogue's typical adult range is stated separately, with the relationship between them recorded rather than collapsed. The catalogue's typical adult range already reaches the largest recorded specimen.
What would improve this: Corroborate against a second, independent source.
lifespanAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
temperaturePublished with one end of the range missingAquariumHQ's own position, derived from evidenced inputs.
A source published one end of the range and left the other unstated.
At least 10 degC — the source does not state an upper boundA chronic thermal minimum of 10 degC, estimated by Bennett et al. (1997). NAS gives no upper limit. A chronic minimum is the temperature below which the animal cannot persist indefinitely, which is a different quantity again from a lethal limit.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Find a source that publishes the missing bound. Do not infer it.
phAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
general hardnessAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
minimum tank volumeAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: minimum tank size — no external source is required, provided AquariumHQ shows its reasoning. No authority publishes this. AquariumHQ derives it, and the derivation is recorded with its inputs and assumptions.
What would improve this: Keep the rationale current. There is no source to find.
minimum tank lengthAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: minimum tank size — no external source is required, provided AquariumHQ shows its reasoning. No authority publishes this. AquariumHQ derives it, and the derivation is recorded with its inputs and assumptions.
What would improve this: Keep the rationale current. There is no source to find.
minimum group sizeAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: group size — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Schooling and shoalingThis species is recorded as shoal, and the number it is kept in decides how it behaves.
- Predator and prey sizeIt takes fish that fit in its mouth, and its mouth grows with it.
- Native, introduced and invasiveThis record carries an invasive or legal note, and those are five separate claims that are easy to read as one.
- Scientific and trade namesThis species has been published under more than one accepted name.
- Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
- Rehoming an animal you can no longer keepThis animal reaches 33 cm. Most of the difficult rehoming cases are fish sold small that were always going to become impossible.
- How to read a compatibility verdictThis animal is recorded as nipping fins, which is one of the few compatibility factors with real reports behind it.
Group size and social behaviour
Shoals for protection. In small numbers or in a tank that is too small the group attacks its own weakest member, and this is the commonest outcome of keeping four in a two-metre tank.