Chili rasbora
One of the smallest fish in the trade at around 2 cm, and a genuine blackwater specialist rather than a general nano fish. In hard alkaline water it survives without ever colouring up properly.
Quick profile
- Scientific name
- Boraras brigittae
- Adult size
- 1.6–2 cm (0.6–0.8 in)
- Lifespan
- 2–4 years
- Temperature
- 24–28 °C (75–82 °F)
- pH
- 4–7
- Hardness
- 1–5 °dGH
- Minimum tank
- 30 L (8 US gal)
- Minimum length
- 40 cm
- Swimming zone
- Midwater
- Social
- Shoaling — at least 10
- Diet
- Micropredator
- Overall confidence
- moderate confidence
What keeping this species involves
Needs soft acidic water, gentle flow and very small food. Frequently sold as an easy nano fish.
Blackwater peat swamps — pH often below 5, almost no dissolved minerals.
Identity and names
- Common name
- Chili rasbora
- Scientific name
- Boraras brigittae
- Family
- Danionidae
- Order
- Cypriniformes
- Class
- Actinopterygii
- Also sold as
- mosquito rasbora
Adult size and growth
1.6–2 cm (0.6–0.8 in)
Typical lifespan in an aquarium: 2–4 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
Small, slow and short-range. A 40 cm tank supports a proper group, and a proper group is what the species needs.
| Requirement | Value | Notes |
|---|---|---|
| Temperature | 24–28 °C (75–82 °F) | Stability matters more than hitting an exact figure. |
| pH | 4–7 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 1–5 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 30 L (8 US gal) | A floor, not a recommendation. |
| Minimum footprint | 40 cm long | Small, slow and short-range. A 40 cm tank supports a proper group, and a proper group is what the species needs. |
| Water flow | still | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Dense planting, leaf litter and dim light. |
Behaviour
- Safe with adult dwarf shrimp and with most shrimplets.
Telling males from females
Males are intensely red with a black lateral line; females are rounder and duller.
Feeding
Mouth is too small for standard flake.
- Diet type
- Micropredator
- Staples
- Powdered dry foods, Baby brine shrimp, Micro-worm, Frozen cyclops
Breeding
- Strategy
- Continuous egg-scattering in moss
- Difficulty
- straightforward
- 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 | low | 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.
- Too small to compete with anything faster. Best kept in a species tank or with other nano 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
- South-western Borneo, Indonesia
- Habitat
- Blackwater peat swamps — pH often below 5, almost no dissolved minerals.
What the checklists say
2 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 |
|---|---|---|
| Recorded as present, establishment means not stated | 2 | The source records the species as present and does not say whether it is native or introduced. AquariumHQ does not fill that in. |
No checklist AquariumHQ holds positively calls this species native anywhere, so the native range above rests on AquariumHQ’s own reading of the literature rather than on a cited checklist.
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 | Boraras brigittae | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | South-western Borneo, Indonesia | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 1.6–2 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 2–4 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 24–28 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 4–7 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 1–5 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 30 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 40 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 10 | 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 fishbase on 2026-08-11. 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 checkableLimited evidence — treat with caution.
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. 2 distribution statements held, and not one of them states an establishment means. Presence without native-or-introduced is not a native-range claim, so this stays below requirement rather than being read as one.
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.
- 3.5 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.
temperatureOne sourceAquariumHQ's own position, derived from evidenced inputs.1 citation, 1 independent origin
A single source: fishbase.
- 25–28 °C — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. Derived from the observed range rather than copied from it. The advised band reaches past the observed envelope and carries no individual review. Commercially bred stock is generally more tolerant than wild records suggest, which is the usual explanation, and it has not been established for this species.
What would improve this: Corroborate against a second, independent source.
phOne sourceAquariumHQ's own position, derived from evidenced inputs.1 citation, 1 independent origin
A single source: fishbase.
- 6.5–7 pH — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. Derived from the observed range rather than copied from it. AquariumHQ advises pH 4.0–7.0; FishBase records 6.5–7.0. The recorded range is implausibly narrow — half a pH unit — for a peat-swamp fish. Boraras brigittae comes from Bornean blackwater where pH routinely sits between 3.5 and 5.0, and a range that excludes acid water entirely does not describe that habitat. The narrowness itself is the tell: it reads as a single site's reading rather than a species envelope. AquariumHQ's range is the one consistent with where the fish actually lives.
What would improve this: Corroborate against a second, independent source.
general hardnessPublished 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.
No more than 10 dGH — the source does not state a lower boundFishBase gives the dH range as '? - 10'. The upper bound is published and the lower is not, so the finding is recorded as a constraint — no harder than 10 dGH — rather than completed with an invented floor.
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.
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
Hides almost permanently in small groups. Ten is a floor, not a target.