Rummy-nose tetra
The tightest-schooling tetra in general trade, and the one whose face doubles as a water-quality meter — the red head colour fades within hours of a water quality problem and returns when it is corrected.
Quick profile
- Scientific name
- Hemigrammus rhodostomus
- Adult size
- 4.5–5 cm (1.8–2 in)
- Lifespan
- 4–6 years
- Temperature
- 24–28 °C (75–82 °F)
- pH
- 5–7
- Hardness
- 1–8 °dGH
- Minimum tank
- 90 L (24 US gal)
- Minimum length
- 80 cm
- Swimming zone
- Midwater
- Social
- Schooling — at least 8
- Diet
- Micropredator
- Overall confidence
- high confidence
What keeping this species involves
Sensitive to nitrogenous waste and to unstable water; the classic species to lose in an immature tank.
Soft, acidic tributaries and flooded forest margins.
Identity and names
- Common name
- Rummy-nose tetra
- Scientific name
- Hemigrammus rhodostomus
- Family
- Characidae
- Order
- Characiformes
- Class
- Actinopterygii
- Also sold as
- rummynose, red-nose tetra, firehead tetra, Petitella rhodostoma
Name ambiguity
Three species are sold interchangeably as rummy-nose tetra: Hemigrammus rhodostomus, Petitella bleheri (often listed as Hemigrammus bleheri) and Petitella georgiae. They differ in the extent of the red on the head and in the black-and-white tail pattern. Husbandry is close enough that the trade does not distinguish them, but a shop label is not a reliable identification.
Adult size and growth
4.5–5 cm (1.8–2 in)
Typical lifespan in an aquarium: 4–6 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.
Water and tank requirements
A genuinely schooling fish that swims in coordinated laps. Below about 80 cm the school spends its time turning rather than swimming.
| Requirement | Value | Notes |
|---|---|---|
| Temperature | 24–28 °C (75–82 °F) | Stability matters more than hitting an exact figure. |
| pH | 5–7 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 1–8 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 90 L (24 US gal) | A floor, not a recommendation. |
| Minimum footprint | 80 cm long | A genuinely schooling fish that swims in coordinated laps. Below about 80 cm the school spends its time turning rather than swimming. |
| Water flow | moderate | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
Behaviour
- The red head marking is a genuine diagnostic: it fades under poor water quality, stress or illness.
- Swims in coordinated formation, using more length than an equivalent number of loose shoalers.
Feeding
- Diet type
- Micropredator
- Staples
- Small dry foods, Frozen daphnia, Frozen bloodworm (chopped)
Breeding
- Strategy
- Egg-scattering in very soft water
- Difficulty
- challenging
- Parental care
- none
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 | none | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | none | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | moderate | Determines whether a shrimp colony can grow rather than merely persist. |
| Snails | none | Applies to snails you wanted as well as snails you did not. |
| Long or trailing fins | none | Fin damage is an entry point for secondary infection. |
| Plants | none | Tough species such as Anubias and Java fern survive most grazers. |
Assessed pairings
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.
- Do not add to a newly cycled tank. This species reliably reveals a filter that is not yet mature.
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
- Lower Amazon basin — Brazil; related species in the upper Rio Negro and Peru
- Habitat
- Soft, acidic tributaries and flooded forest margins.
What the checklists say
6 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. |
| 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 | Hemigrammus rhodostomus | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Lower Amazon basin — Brazil; related species in the upper Rio Negro and Peru | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 4.5–5 cm | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| lifespan | 4–6 years | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| temperature | 24–28 °C | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| ph | 5–7 pH | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| general hardness | 1–8 °dGH | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 90 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 80 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 8 | AquariumHQ editorial position | high 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 fishbase on 2026-08-11. One authoritative backbone is what this class requires, and the source files it under "Petitella rhodostoma" — both names are searchable.
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. 6 distribution statements held from GBIF checklists — native in 1 country. 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 sourceBased on a verified authoritative source.1 citation, 1 independent origin
A single source: fishbase.
- 5 cm — FishBase · Maximum recorded · The range the species is recorded from · checked 2026-08-11
What this kind of claim needs: size a well-kept specimen reaches — no external source is required, provided AquariumHQ shows its reasoning. One authoritative source, which is what this kind of claim requires. Independent replication would be welcome and is not the standard.
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.
temperatureChecked — this source does not publish itAquariumHQ's own position, derived from evidenced inputs.
A source was opened and checked for this, and does not publish it.
Checked and not published. Checked in the environment field. FishBase publishes no environmental temperature range for this species.
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: Look elsewhere. This source has been exhausted for this claim.
phChecked — this source does not publish itAquariumHQ's own position, derived from evidenced inputs.
A source was opened and checked for this, and does not publish it.
Checked and not published. Checked in the environment field. FishBase publishes no pH range for this species.
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: Look elsewhere. This source has been exhausted for this claim.
general hardnessChecked — this source does not publish itAquariumHQ's own position, derived from evidenced inputs.
A source was opened and checked for this, and does not publish it.
Checked and not published. Checked in the environment field. FishBase publishes no dH range for this species.
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: Look elsewhere. This source has been exhausted for this claim.
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.
Group size and social behaviour
One of the few aquarium fish that truly schools rather than shoals. Numbers matter.