Siamese fighting fish
The fish most often kept in conditions that would be unacceptable for anything else. The labyrinth organ lets a betta breathe air, which is why it survives in unfiltered bowls — surviving low oxygen is not the same as needing little space, and a betta in a heated, filtered, planted tank behaves like a different animal.
Quick profile
- Scientific name
- Betta splendens
- Adult size
- 5–7 cm (2–2.8 in)
- Lifespan
- 2–4 years
- Temperature
- 24–28 °C (75–82 °F)
- pH
- 6–7.5
- Hardness
- 2–15 °dGH
- Minimum tank
- 20 L (5 US gal)
- Minimum length
- 40 cm
- Swimming zone
- All levels
- Social
- Solitary and territorial
- Diet
- Carnivore
- Overall confidence
- high confidence
What keeping this species involves
Needs a heater, a filter with gentle flow and a lid. Long-finned strains are poor swimmers and prone to fin problems.
Shallow, still, densely vegetated floodplain and paddy habitats. Warm, soft and low in oxygen — which is what the labyrinth organ is for.
Identity and names
- Common name
- Siamese fighting fish
- Scientific name
- Betta splendens
- Family
- Osphronemidae
- Order
- Anabantiformes
- Class
- Actinopterygii
- Also sold as
- betta, betta splendens, fighting fish
Varieties and strains
| Variety | What it means in practice |
|---|---|
| Veiltail | The original long-finned form. Fin weight makes swimming laborious. |
| Halfmoon and rosetail | Extreme finnage; rosetails in particular are prone to fin curling and tearing. |
| Plakat | Short-finned. Swims far better and is generally more robust. |
| Giant | Selectively bred to 7–8 cm; needs a proportionately larger tank. |
Adult size and growth
5–7 cm (2–2.8 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
Twenty litres is the smallest volume that holds stable temperature and chemistry with a heater and filter in it. It is a floor, not a recommendation — bettas in 40–60 L planted tanks are visibly more active and explore far more.
| Requirement | Value | Notes |
|---|---|---|
| Temperature | 24–28 °C (75–82 °F) | Stability matters more than hitting an exact figure. |
| pH | 6–7.5 | 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 | 20 L (5 US gal) | A floor, not a recommendation. |
| Minimum footprint | 40 cm long | Twenty litres is the smallest volume that holds stable temperature and chemistry with a heater and filter in it. It is a floor, not a recommendation — bettas in 40–60 L planted tanks are visibly more active and explore far more. |
| Water flow | still | Match the outflow to this rather than to the filter's rating. |
| Lid required | Yes | This species jumps. |
| Structure | Broad-leaved plants to rest on near the surface, floating cover, and no strong current. |
Behaviour
- Breathes atmospheric air at the surface — the tank must never be filled to the rim or sealed without an air gap.
- Flares at reflections and at other fish; sustained flaring is stress, not exercise.
- Individual temperament varies enormously, which makes blanket tankmate advice unreliable.
Telling males from females
Males have greatly extended fins and stronger colour; females are shorter-finned with an ovipositor spot.
Feeding
A genuine carnivore. Plant-based flake is poorly digested.
- Diet type
- Carnivore
- Staples
- Betta-specific dry foods, Frozen bloodworm and daphnia, Live blackworm
Breeding
- Strategy
- Bubble-nest builder; the male tends the nest
- Difficulty
- straightforward
- Parental care
- guarding
The male guards eggs and fry. The female must be removed after spawning.
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 | low | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | moderate | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | high | 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.
- Unheated, unfiltered bowls and vases are unsuitable. This is the single most common welfare failure in the hobby.
- Jumps; a lid with a small air gap above the water is essential.
- Sold in small cups after long transport. Expect a settling-in period and quarantine.
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
- Central Thailand — Chao Phraya basin and adjacent floodplains
- Habitat
- Shallow, still, densely vegetated floodplain and paddy habitats. Warm, soft and low in oxygen — which is what the labyrinth organ is for.
What the checklists say
16 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 |
|---|---|---|
| Introduced | 12 | 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 | 4 | 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 | Betta splendens | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Central Thailand — Chao Phraya basin and adjacent floodplains | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 5–7 cm | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| lifespan | 2–4 years | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| temperature | 24–28 °C | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| ph | 6–7.5 pH | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| general hardness | 2–15 °dGH | Aquarium-literature consensus | high confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 20 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 40 cm | 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 2026-08-11. 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 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. 16 distribution statements held from GBIF checklists — introduced in 11 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 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.
temperatureIndependently verifiedConfirmed by more than one independent source.3 citations, 3 independent origins
3 citations from 3 independent origins.
- 25–28 °C — AquariumHQ husbandry synthesis · Recommended for keeping · Recommended for keeping · checked 2026-08-11
- 24–30 °C — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11
- 20–28 °C — Ornamental Aquatic Trade Association · Recommended for keeping · Recommended for keeping · checked 2026-08-11Corrected on checking from 24–28 °C.
- 27–31.5 °C — UF/IFAS Extension — fish health and aquaculture publications · Observed in the wild · Observed in the wild · checked 2026-08-11Corrected on checking from 78–82 °F.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. 3 independent origins.
What would improve this: Nothing. Recheck when the sources are next reviewed.
phIndependently verifiedConfirmed by more than one independent source.2 citations, 2 independent origins
2 citations from 2 independent origins.
- 6–8 pH — Ornamental Aquatic Trade Association · Recommended for keeping · Recommended for keeping · checked 2026-08-11
- 5.28–5.8 pH — UF/IFAS Extension — fish health and aquaculture publications · Observed in the wild · Observed in the wild · 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. 2 independent origins.
What would improve this: Nothing. Recheck when the sources are next reviewed.
general hardnessOne sourceBased on a verified authoritative source.1 citation, 1 independent origin
A single source: oata.
- 4–12 °dGH — Ornamental Aquatic Trade Association · Recommended for keeping · Recommended for keeping · 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. 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.
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.
Group size and social behaviour
Males cannot be kept together under any circumstances. Females can sometimes be kept as a group ('sorority'), but this requires a large, heavily planted tank, careful selection and a contingency plan — it fails often enough that AquariumHQ does not recommend it as a default.