Royal pleco
A grey-and-black striped pleco with red eyes that rasps and ingests wood, relying on gut microbes to extract what it can from it. It reaches over forty centimetres, needs a permanent supply of soft wood, and is not an algae eater in any useful sense.
Quick profile
- Scientific name
- Panaque nigrolineatus
- Adult size
- 35–45 cm (13.8–17.7 in)
- Lifespan
- 10–20 years
- Temperature
- 24–29 °C (75–84 °F)
- pH
- 6.2–7.6
- Hardness
- 2–15 °dGH
- Minimum tank
- 600 L (159 US gal)
- Minimum length
- 180 cm
- Swimming zone
- Bottom
- Social
- Solitary and territorial
- Diet
- Wood-rasping
- Overall confidence
- moderate confidence
What keeping this species involves
A forty-five-centimetre fish with an unusual dietary requirement, a long life and a real intolerance of its own kind. Providing wood is easy; providing the tank is not.
Fast river reaches with large accumulations of submerged wood, which the fish rasps and lives among.
Identity and names
- Common name
- Royal pleco
- Scientific name
- Panaque nigrolineatus
- Family
- Loricariidae
- Order
- Siluriformes
- Class
- Actinopterygii
- Also sold as
- Panaque nigrolineatus, L027, L190, royal panaque
Name ambiguity
Several regional forms are traded under this name and under separate L-numbers, and the boundaries between them are unresolved. The husbandry is the same across the group; the identification on a shop label frequently is not a determination.
Adult size and growth
35–45 cm (13.8–17.7 in)
Typical lifespan in an aquarium: 10–20 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: depressed — flattened top to bottom with a grazing or sucking mouth. Assigned from what is typical of Loricariidae, not examined for this species.
Water and tank requirements
A fish reaching forty-five centimetres that spends its life on and around large pieces of wood. Both the fish and the wood have to fit, and the wood is not optional.
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: Amazon and Orinoco main-channel water, soft to moderate and near-neutral, well oxygenated. Flow and oxygen matter more to this fish than the chemistry does.
Where these figures come from
Habitat class
Clearwater lowland river
Transparent, mineral-poor rivers draining ancient shield geology — the Tapajós and Xingu type — with low sediment and good light penetration.
Soft water with more movement and more oxygen than a forest stream. Species from here generally want current and open swimming room as much as they want the chemistry.
- Conductivity
- 20–100 µS/cm
- Flow
- moderate
- Dissolved oxygen
- near saturation
- 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 | 24–29 °C (75–84 °F) | Stability matters more than hitting an exact figure. |
| pH | 6.2–7.6 | 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 | 600 L (159 US gal) | A floor, not a recommendation. |
| Minimum footprint | 180 cm long × 60 cm deep | A fish reaching forty-five centimetres that spends its life on and around large pieces of wood. Both the fish and the wood have to fit, and the wood is not optional. |
| Water flow | high | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Large pieces of soft wood — bogwood or similar — as the principal furnishing, with strong flow and high oxygen. The wood is food and habitat at once. |
Behaviour
- Rasps visible grooves into soft wood and produces large quantities of sawdust-like waste, which is a normal output rather than a filtration failure.
- Rests attached to the underside of wood through the day and works at it after dark.
Telling males from females
Mature males develop odontodes on the pectoral spines and the head. Females are broader-bodied. Neither is readable in juveniles.
Feeding
Wood is a genuine dietary requirement rather than a chewing habit, and a high-protein diet is associated with bloating and digestive failure in this genus. Vegetable food supplements the wood; it does not replace it.
- Diet type
- Wood-rasping
- Staples
- Soft bogwood, Blanched courgette, Blanched sweet potato, Vegetable wafers
- Avoid
- High-protein sinking pellets, Bloodworm as a staple
Breeding
- Strategy
- Cave spawning with the male guarding the eggs
- Difficulty
- rarely achieved
- Parental care
- guarding
Very rarely achieved in aquaria. Most trade stock is wild-caught.
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. |
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.
- Sold as an algae eater. It is a wood specialist that will not control algae and will starve on a diet designed for one.
- Produces a very high volume of waste for its size because most of what it eats passes through. Filtration and water changes have to be planned around that rather than around the fish's length.
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 Orinoco and Amazon basins — Colombia, Venezuela, Brazil and Peru
- Habitat
- Fast river reaches with large accumulations of submerged wood, which the fish rasps and lives among.
What the checklists say
11 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 | 3 | A checklist states the species occurs here naturally. |
| Introduced | 2 | 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 | 6 | 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 | Panaque nigrolineatus | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | The Orinoco and Amazon basins — Colombia, Venezuela, Brazil and Peru | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 35–45 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 10–20 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 24–29 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 6.2–7.6 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 2–15 °dGH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank volume | ≥ 600 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 180 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 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. 11 distribution statements held from GBIF checklists — native in 3, introduced in 2 countries. 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.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Territorial behaviourIt defends ground, and the shape of what it defends decides the tank more than the volume does.
- Scientific and trade namesThe trade name for this animal covers more than one species.
- Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
- Rehoming an animal you can no longer keepThis animal reaches 45 cm. Most of the difficult rehoming cases are fish sold small that were always going to become impossible.
Group size and social behaviour
Territorial with its own kind and with other large loricariids. One per tank unless the aquarium is genuinely large and has several separate wood structures.