Uaru
A deep-bodied Amazonian cichlid with a large dark triangle on the flank, kept in groups and unusual among large cichlids in requiring a substantially vegetable diet. Juveniles are spotted black and white and look nothing like the adults.
Quick profile
- Scientific name
- Uaru amphiacanthoides
- Adult size
- 20–25 cm (7.9–9.8 in)
- Lifespan
- 8–12 years
- Temperature
- 26–30 °C (79–86 °F)
- pH
- 4.5–6.5
- Hardness
- 0–5 °dGH
- Minimum tank
- 450 L (119 US gal)
- Minimum length
- 150 cm
- Swimming zone
- Midwater
- Social
- Loose group — at least 5
- Diet
- Omnivore
- Overall confidence
- moderate confidence
What keeping this species involves
Very soft acidic water, a vegetable-based diet, a group of five at twenty-five centimetres, and a nervous temperament that punishes a busy tank. The combination is a species tank.
Slow blackwater and clearwater margins among submerged wood and drowned vegetation, in soft acidic water.
Identity and names
- Common name
- Uaru
- Scientific name
- Uaru amphiacanthoides
- Family
- Cichlidae
- Order
- Cichliformes
- Class
- Actinopterygii
- Also sold as
- Uaru amphiacanthoides, triangle cichlid, waroo, chocolate cichlid
Adult size and growth
20–25 cm (7.9–9.8 in)
Typical lifespan in an aquarium: 8–12 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: deep-bodied with a moderate. Assigned from what is typical of Cichlidae, not examined for this species.
Water and tank requirements
A deep-bodied group fish of around twenty-five centimetres that needs both swimming length and enough height not to be crowded vertically.
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: Rio Negro blackwater and comparable soft clear waters. This is one of the large cichlids for which very soft acidic water is a genuine requirement rather than an optimisation, and hard water is associated with poor condition and short lives.
Where these figures come from
Habitat class
Blackwater
Tannin-stained water draining podzolic forest sand, carrying almost no dissolved mineral and a heavy load of humic and fulvic acid.
The defining property is the absence of mineral, not the colour. Water this soft has almost no buffering, so pH moves fast and a keeper's job is stability rather than chasing the wild figure.
- Conductivity
- 8–40 µS/cm
- Flow
- low
- Dissolved oxygen
- moderate
- 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 | 26–30 °C (79–86 °F) | Stability matters more than hitting an exact figure. |
| pH | 4.5–6.5 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 0–5 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 450 L (119 US gal) | A floor, not a recommendation. |
| Minimum footprint | 150 cm long × 50 cm deep | A deep-bodied group fish of around twenty-five centimetres that needs both swimming length and enough height not to be crowded vertically. |
| Water flow | low | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Tall wood, leaf litter and botanicals. The wood is used as cover and the litter as both food and shelter. |
Behaviour
- Hangs among vertical wood and moves in short unhurried repositionings rather than swimming laps.
- Bolts hard at sudden movement outside the tank, and a startled group will collide with hardscape, so the layout needs to be free of sharp edges.
Telling males from females
No reliable external difference outside spawning.
Feeding
Takes a large proportion of plant material in the wild and needs vegetable food as a staple rather than a supplement. A purely protein diet produces digestive problems and poor growth.
- Diet type
- Omnivore
- Staples
- Blanched courgette, Spirulina pellets, Blanched spinach, Frozen mysis, Peas
Breeding
- Strategy
- Adhesive eggs on a vertical surface, guarded by both parents
- Difficulty
- challenging
- Parental care
- guarding
Fry feed on parental skin mucus in the first days, as discus do, which makes removing the parents counterproductive.
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 | moderate | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | high | 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 | low | Applies to snails you wanted as well as snails you did not. |
| Long or trailing fins | occasional | Fin damage is an entry point for secondary infection. |
| Plants | consumes | 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.
- Will strip most aquarium plants. A planted tank and a group of these are not compatible, and the fish is not being destructive so much as eating.
- Juvenile and adult patterns are entirely different. A keeper expecting the spotted juvenile to keep its markings has bought the wrong picture of the fish.
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 and Rio Negro basins of Brazil, and the Essequibo in Guyana
- Habitat
- Slow blackwater and clearwater margins among submerged wood and drowned vegetation, in soft acidic water.
What the checklists say
7 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 | 1 | A checklist states the species occurs here naturally. |
| Introduced | 1 | 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. |
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 | Uaru amphiacanthoides | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | The Amazon and Rio Negro basins of Brazil, and the Essequibo in Guyana | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 20–25 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 8–12 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 26–30 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 4.5–6.5 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 0–5 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 450 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 150 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. 7 distribution statements held from GBIF checklists — native in 1, introduced in 1 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 sizeAquariumHQ'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: size a well-kept specimen reaches — 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.
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.
temperatureAquariumHQ'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.
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 loose group, and the number it is kept in decides how it behaves.
- Predator and prey sizeIt takes adult dwarf shrimp, which decides what can share the tank.
- 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 25 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
A group fish that pairs from the group. Kept in twos and threes the fish are nervous and colour poorly, which is the usual reason a solitary specimen looks so unimpressive.