Licorice gourami
A three-centimetre blackwater gourami whose males display with red-and-blue banded fins in a courtship performed upside down inside a cave. The genus is among the most threatened groups of freshwater fish in the aquarium hobby and is the subject of an organised conservation-breeding effort.
Quick profile
- Scientific name
- Parosphromenus deissneri
- Adult size
- 2.5–3.5 cm (1–1.4 in)
- Lifespan
- 2–4 years
- Temperature
- 23–27 °C (73–81 °F)
- pH
- 4–5.5
- Hardness
- 0–2 °dGH
- Minimum tank
- 25 L (7 US gal)
- Minimum length
- 40 cm
- Swimming zone
- Bottom
- Social
- Pair
- Diet
- Micropredator
- Overall confidence
- moderate confidence
What keeping this species involves
Water that has to be prepared rather than treated, live food only, and a fish under four centimetres that cannot share a tank with anything. It is a species-tank animal for an experienced keeper.
Shallow blackwater peat swamp streams under forest cover, stained almost black, extremely soft and acidic.
Identity and names
- Common name
- Licorice gourami
- Scientific name
- Parosphromenus deissneri
- Family
- Osphronemidae
- Order
- Anabantiformes
- Class
- Actinopterygii
- Also sold as
- Parosphromenus deissneri, deissneri, liquorice gourami, paro
Adult size and growth
2.5–3.5 cm (1–1.4 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.
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 holding a single cave in dense litter. The tank is small because a small volume of correctly prepared water is far easier to hold stable than a large one.
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: Bangka peat swamp water is extraordinarily soft and acidic, with conductivity close to that of rainwater. This is not a preference: the species will not spawn and does not persist in ordinary tap water, and reverse osmosis water with botanicals is the normal way of providing it.
Where these figures come from
Habitat class
Peat swamp forest — Bangka Island peat swamp
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 | 23–27 °C (73–81 °F) | Stability matters more than hitting an exact figure. |
| pH | 4–5.5 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 0–2 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 25 L (7 US gal) | A floor, not a recommendation. |
| Minimum footprint | 40 cm long × 25 cm deep | A pair holding a single cave in dense litter. The tank is small because a small volume of correctly prepared water is far easier to hold stable than a large one. |
| Water flow | still | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Deep leaf litter, dense fine planting, small caves and almost no light or flow. Botanicals maintain the chemistry as well as providing structure. |
Behaviour
- Males display in a head-down posture inside or at the mouth of a cave, with every fin spread, holding it for many seconds.
- Spends most of the day motionless among litter and is essentially invisible in a tank without dense cover.
Telling males from females
Males have red-and-blue banded unpaired fins and display them fully; females are plain brown with clear fins.
Feeding
Takes only small live food in most cases and refuses dry food almost universally. A live-food culture is a practical precondition for keeping the genus.
- Diet type
- Micropredator
- Staples
- Live baby brine shrimp, Live daphnia, Live blackworm, Microworm
Breeding
- Strategy
- A small bubble nest inside a cave, tended by the male
- Difficulty
- challenging
- Parental care
- guarding
The male courts by displaying head-down inside the cave and tends a very small clutch. The whole process happens out of sight.
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 | occasional | 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.
- Peat swamp habitat across Bangka and the wider Sundaic region has been heavily lost to drainage, tin mining and plantation. Several Parosphromenus species have very small remaining ranges.
- An international conservation-breeding project maintains named wild populations of this genus in aquaria. Fish obtained through it come with locality data, which is what makes the effort meaningful.
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
- Bangka Island, Indonesia — a very small area of peat swamp
- Habitat
- Shallow blackwater peat swamp streams under forest cover, stained almost black, extremely soft and acidic.
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 | Parosphromenus deissneri | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Bangka Island, Indonesia — a very small area of peat swamp | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 2.5–3.5 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 2–4 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 23–27 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 4–5.5 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 0–2 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 25 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 2026-08-29. 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 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 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.
- 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
Kept as pairs or in small groups in a heavily furnished tank. Males hold caves and display at each other at the boundaries without serious damage.