Amazon leaf fish
A fish shaped, coloured and moving like a drifting dead leaf, complete with a chin barbel that mimics a leaf stalk, which drifts up to prey and engulfs it in a fraction of a second. It eats live fish and very little else, which decides everything about keeping it.
Quick profile
- Scientific name
- Monocirrhus polyacanthus
- Adult size
- 7–10 cm (2.8–3.9 in)
- Lifespan
- 3–5 years
- Temperature
- 25–29 °C (77–84 °F)
- pH
- 4.5–6.5
- Hardness
- 0–5 °dGH
- Minimum tank
- 60 L (16 US gal)
- Minimum length
- 60 cm
- Swimming zone
- Midwater
- Social
- Loose group — at least 2
- Diet
- Piscivore
- Overall confidence
- moderate confidence
What keeping this species involves
A live-food obligate in blackwater conditions. Neither requirement is unusual on its own and together they make this a species-tank fish for an experienced keeper.
Slow shaded blackwater margins among leaf litter and root tangles, with almost no current.
Identity and names
- Common name
- Amazon leaf fish
- Scientific name
- Monocirrhus polyacanthus
- Family
- Polycentridae
- Order
- Perciformes
- Class
- Actinopterygii
- Also sold as
- Monocirrhus polyacanthus, leaf fish, South American leaffish, polyacanthus
Adult size and growth
7–10 cm (2.8–3.9 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: disc — as deep as it is long with a very large — prey approaching its own length. Monocirrhus is a leaf that eats fish nearly its own length through an enormously protrusible jaw. Nothing about its length predicts what it can swallow.
Water and tank requirements
A sedentary ambush predator that drifts rather than swims. Cover and still water matter far more than swimming space.
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: Amazonian blackwater margins, warm, extremely soft and acidic. This species is sensitive to hardness and to dissolved waste, and the water is the second-hardest part of keeping it after the diet.
Where these figures come from
Habitat class
Blackwater
Tannin-stained water draining podzolic forest sand, carrying almost no dissolved mineral and a heavy load of humic and fulvic acid.
The defining property is the absence of mineral, not the colour. Water this soft has almost no buffering, so pH moves fast and a keeper's job is stability rather than chasing the wild figure.
- Conductivity
- 8–40 µS/cm
- Flow
- low
- Dissolved oxygen
- moderate
- Seasonality
- strong
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 | 25–29 °C (77–84 °F) | Stability matters more than hitting an exact figure. |
| pH | 4.5–6.5 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 0–5 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 60 L (16 US gal) | A floor, not a recommendation. |
| Minimum footprint | 60 cm long × 35 cm deep | A sedentary ambush predator that drifts rather than swims. Cover and still water matter far more than swimming space. |
| 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, root tangles, dim light and no perceptible current. The litter is camouflage and hunting ground at once. |
Behaviour
- Drifts head-down at an angle with the body swaying, which reproduces the motion of a leaf in slow water and is how it approaches prey unnoticed.
- Engulfs prey by protruding the jaws into a tube, a strike lasting a small fraction of a second and covering close to its own body length.
Telling males from females
No reliable external difference outside spawning.
Feeding
Takes live moving prey almost exclusively, and most specimens never accept prepared food. Keeping it means maintaining a culture of live food, which is a standing commitment rather than a preference.
- Diet type
- Piscivore
- Staples
- Live livebearer fry, Live river shrimp, Live blackworm
- Avoid
- Dry pellets, Flake
Breeding
- Strategy
- Eggs laid on a leaf or hard surface and guarded by the male
- Difficulty
- challenging
- Parental care
- guarding
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 | near-certain | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | near-certain | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | near-certain | Determines whether a shrimp colony can grow rather than merely persist. |
| Snails | moderate | 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 | uproots | 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.
- Requires live fish or shrimp of appropriate size. A keeper unwilling to maintain that supply should not take the species on, and this is one of the clearest cases in the catalogue where the honest advice is to choose something else.
- Loses condition quietly when underfed because it does not compete visibly for food. Weight loss is easier to see from above than from the front.
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
- The Amazon and Orinoco basins and the Guianas
- Habitat
- Slow shaded blackwater margins among leaf litter and root tangles, with almost no current.
What the checklists say
13 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 | 6 | A checklist states the species occurs here naturally. |
| Recorded as present, establishment means not stated | 7 | 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 | Monocirrhus polyacanthus | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | The Amazon and Orinoco basins and the Guianas | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 7–10 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 3–5 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 25–29 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 4.5–6.5 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 0–5 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 60 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 60 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 2 | 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 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. 13 distribution statements held from GBIF checklists — native in 6 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.
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.
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.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Schooling and shoalingThis species is recorded as loose group, and the number it is kept in decides how it behaves.
- Predator and prey sizeIt takes fish that fit in its mouth, and its mouth grows with it.
- 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
Tolerant of its own kind where there is enough cover and enough food. Competition is over feeding rather than territory.