Midnight betta
A small, near-black mouthbrooding Betta from a handful of Johor peat swamps, most of which have been cleared. It is one of the most threatened fish in the aquarium trade, and the population held by hobbyists is a meaningful part of what remains of the species.
Quick profile
- Scientific name
- Betta persephone
- Adult size
- 3–4 cm (1.2–1.6 in)
- Lifespan
- 3–5 years
- Temperature
- 22–27 °C (72–81 °F)
- pH
- 4–6
- Hardness
- 0–3 °dGH
- Minimum tank
- 30 L (8 US gal)
- Minimum length
- 45 cm
- Swimming zone
- Bottom
- Social
- Pair
- Diet
- Micropredator
- Overall confidence
- low confidence
What keeping this species involves
Requires blackwater chemistry it will not thrive without, live food, deep litter and total shade. It is a conservation-relevant species kept by specialists and should not be a first betta.
Blackwater peat swamp forest under closed canopy: shallow, still, deeply stained water over thick leaf litter, strongly acidic and almost mineral-free.
Identity and names
- Common name
- Midnight betta
- Scientific name
- Betta persephone
- Family
- Osphronemidae
- Order
- Anabantiformes
- Class
- Actinopterygii
- Also sold as
- Betta persephone, black small betta, Persephone betta
Adult size and growth
3–4 cm (1.2–1.6 in)
Typical lifespan in an aquarium: 3–5 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 small terminal mouth. Assigned from what is typical of Osphronemidae, not examined for this species.
Water and tank requirements
A pair holds a small area of litter and needs a defended patch plus a retreat for the fish that is losing. Floor area with deep cover rather than volume.
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: Johor peat swamp: pH commonly between 4 and 5 and hardness at the limit of what a test kit resolves. This band is the habitat, and unlike most peat-swamp species in this catalogue it is NOT advised above it — the fish declines and will not spawn in anything harder.
Where these figures come from
Habitat class
Peat swamp forest — Johor peat swamp remnants
Standing or barely-moving water over deep peat, in Sundaland and analogous systems. The most acidic fresh water routinely inhabited by aquarium fish.
Species from here are adapted to oxygen levels that would kill most fish, which is why so many of them breathe air. The pH is genuinely extreme and generally does NOT have to be reproduced for maintenance, only for breeding.
- Conductivity
- 10–70 µS/cm
- Flow
- still
- Dissolved oxygen
- low
- Seasonality
- moderate
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 | 22–27 °C (72–81 °F) | Stability matters more than hitting an exact figure. |
| pH | 4–6 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 0–3 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 30 L (8 US gal) | A floor, not a recommendation. |
| Minimum footprint | 45 cm long | A pair holds a small area of litter and needs a defended patch plus a retreat for the fish that is losing. Floor area with deep cover rather than volume. |
| Water flow | still | Match the outflow to this rather than to the filter's rating. |
| Lid required | Yes | Reduces evaporation and prevents accidents. |
| Structure | Deep leaf litter, blackwater tannins, no substrate to speak of, floating plants and total shade. |
Behaviour
- Spends almost all its time in or immediately above leaf litter and is frequently invisible for days.
- The male's brooding is silent and easy to miss — a brooding male simply stops feeding.
Telling males from females
Males are larger, darker and develop a broader head for brooding; females are browner with a paler throat.
Feeding
Takes almost no dry food. Live or frozen is effectively a requirement rather than a preference.
- Diet type
- Micropredator
- Staples
- Live blackworm and grindal worm, Frozen bloodworm and cyclops, Live daphnia
Breeding
- Strategy
- Paternal mouthbrooding — the male carries the eggs and fry for around ten days
- Difficulty
- challenging
- Parental care
- mouthbrooding
Requires genuinely blackwater conditions. Attempts in tap water fail at the egg stage rather than at the spawning stage, which makes the cause hard to see.
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 | 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 | low | 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. |
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.
- Assessed as critically threatened in the wild by the conservation literature, with its peat swamp habitat largely cleared. Aquarium populations maintained by specialist networks are a genuine reserve.
- Do not mix with other Betta species. The genus hybridises and a hybrid line of a threatened species is worse than no line.
- Needs a fully covered tank. Every Betta jumps and this one is small enough to leave through a filter cut-out.
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
- Peninsular Malaysia — Johor state, in a very small number of peat swamp remnants
- Habitat
- Blackwater peat swamp forest under closed canopy: shallow, still, deeply stained water over thick leaf litter, strongly acidic and almost mineral-free.
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 persephone | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Peninsular Malaysia — Johor state, in a very small number of peat swamp remnants | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 3–4 cm | Aquarium-literature consensus | low confidence | AquariumHQ husbandry synthesis |
| lifespan | 3–5 years | Aquarium-literature consensus | low confidence | AquariumHQ husbandry synthesis |
| temperature | 22–27 °C | Aquarium-literature consensus | low confidence | AquariumHQ husbandry synthesis |
| ph | 4–6 pH | Aquarium-literature consensus | low confidence | AquariumHQ husbandry synthesis |
| general hardness | 0–3 °dGH | Aquarium-literature consensus | low confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 30 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 45 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 2026-08-30. 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. No checklist distribution statement is held for this species. The range on the page is editorial until one is.
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.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
Group size and social behaviour
Forms pairs. Males spar and a tank without enough cover produces one survivor. Best kept as a single pair or a species colony in a large heavily littered tank.