Spotted scat
A deep-bodied spotted estuarine fish whose scientific name means dung-eater, reflecting where it is often found feeding. It reaches over thirty centimetres, carries venomous dorsal spines, and moves from brackish to marine conditions as it matures.
Quick profile
- Scientific name
- Scatophagus argus
- Adult size
- 25–35 cm (9.8–13.8 in)
- Lifespan
- 8–15 years
- Temperature
- 24–28 °C (75–82 °F)
- pH
- 7.8–8.5
- Hardness
- 12–30 °dGH
- Minimum tank
- 600 L (159 US gal)
- Minimum length
- 180 cm
- Swimming zone
- All levels
- Social
- Loose group — at least 3
- Diet
- Omnivore
- Overall confidence
- moderate confidence
What keeping this species involves
A large estuarine fish with a rising salinity requirement, a vegetable diet and venomous spines. Sold as a small freshwater ornamental with none of that stated.
Estuaries, mangrove creeks, harbours and coastal waters, with juveniles in low-salinity habitat and adults in seawater.
Identity and names
- Common name
- Spotted scat
- Scientific name
- Scatophagus argus
- Family
- Scatophagidae
- Order
- Perciformes
- Class
- Actinopterygii
- Also sold as
- Scatophagus argus, scat, argus fish, green scat, red scat
Adult size and growth
25–35 cm (9.8–13.8 in)
Typical lifespan in an aquarium: 8–15 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 small terminal mouth. A brackish disc with a small grazing mouth.
Water and tank requirements
A deep-bodied fish reaching thirty-five centimetres, kept in groups. Both height and length are constraints.
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: An estuarine species whose salinity requirement rises with age, from near-fresh juvenile habitat to full seawater. As with the monos, a single freshwater band would misrepresent the life history.
Where these figures come from
Habitat class
Brackish and estuarine
Water where fresh meets salt — estuaries, mangrove, tidal creeks and coastal lagoons — with salinity that changes with the tide.
Salinity is a requirement, not a tolerance, for the species genuinely from here — and the commonest way these animals are killed is being sold and kept as freshwater fish.
- Conductivity
- 2000–35000 µS/cm
- Salinity
- 1–20 ppt
- Flow
- variable
- Dissolved oxygen
- moderate
- 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 | 24–28 °C (75–82 °F) | Stability matters more than hitting an exact figure. |
| pH | 7.8–8.5 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 12–30 °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 deep-bodied fish reaching thirty-five centimetres, kept in groups. Both height and length are constraints. |
| Water flow | moderate | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Open water with rock or root structure, high salinity and heavy filtration. Plants will be eaten and are not part of the setup in any case. |
Behaviour
- Grazes surfaces continuously and works over any soft plant material within reach.
- Raises the spiny dorsal fin when threatened, which is a warning rather than a bluff.
Telling males from females
No reliable external difference.
Feeding
Substantially herbivorous as well as detritivorous. Vegetable food is a real requirement and it will strip any plant in the tank.
- Diet type
- Omnivore
- Staples
- Nori sheet, Frozen mysis, Marine flake, Blanched courgette
Breeding
- Strategy
- Open-water spawning in coastal seawater; not achieved in aquaria
- Difficulty
- rarely achieved
- Parental care
- none
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 | high | 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 | 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 | consumes | 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.
- The dorsal spines carry venom and a puncture is painful and occasionally serious. Handle with a rigid container rather than a net or bare hands, and treat any sting as a medical matter.
- The red and green forms sold as separate fish are colour variants of one species, and juvenile red colour fades with age.
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
- Indo-Pacific coasts — from the Persian Gulf and East Africa to Japan and Australia
- Habitat
- Estuaries, mangrove creeks, harbours and coastal waters, with juveniles in low-salinity habitat and adults in seawater.
What the checklists say
12 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 | 5 | 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 | 7 | 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.
Legal status and responsible practice
Where this species has been introduced, and what followed
Europe — a single Maltese record from 2007
Recorded, not establishedOne record, from Malta in 2007, published as an overlooked and unexpected introduction. A brackish and marine-tolerant species in the Mediterranean is a different kind of risk from a freshwater one, because the sea is not a barrier to it.
- Deliberate stockingSomebody put the species into open water on purpose, for food, angling, ornament or mosquito control — frequently a government agency, and frequently before anyone considered the consequences.
What has been established
Nothing. The species is present outside its native range and no study has measured what it does there. The absence of data is not the absence of effect — it means the question has not been asked, and this is the ordinary state of the evidence for most aquarium species that have established somewhere warm.
EASIN — European Alien Species Information Network · EASIN catalogue record R16818 (apixg/catxg) · read 2026-08-30. A European network: the routes and effects recorded here are the ones documented in Europe. EASIN compiles national inventories, DAISIE and CABI rather than measuring, and its pathway assignments carry its own uncertainty flags, which are reported above where it sets them.
Never release aquarium life into the wild
Aquarium animals, plants, and aquarium water must never be released into ponds, rivers, canals, drains or the sea — not even in a country where the species is sold freely. Released fish and invertebrates establish populations that displace native species, and released plants and water carry pathogens, parasites and fragments capable of spreading without any animal at all. If you can no longer keep an animal, rehome it through an aquarium society, a retailer that accepts returns, or another keeper.
- Rehome through a local aquarium society, a specialist retailer or another keeper.
- Unwanted plants go in household waste or a hot compost heap, never in a watercourse or a garden pond.
- Never empty a bucket of tank water into a drain that discharges to open water.
- If an animal is beyond rehoming, ask an aquatic veterinarian about humane euthanasia rather than releasing it.
Legal status is recorded from the sources named and was correct on the verification date shown. Rules change, and sub-national rules often differ from national ones. Check the current position with the relevant authority before acquiring, selling or moving any animal or plant.
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 | Scatophagus argus | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Indo-Pacific coasts — from the Persian Gulf and East Africa to Japan and Australia | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 25–35 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 8–15 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 24–28 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 7.8–8.5 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 12–30 °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 |
| minimum group size | ≥ 3 | 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. 12 distribution statements held from GBIF checklists — introduced in 5 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.
- How aquarium species get into the wildThis species has a documented introduction outside its native range, with the route recorded.
- Rehoming an animal you can no longer keepThis animal reaches 35 cm. Most of the difficult rehoming cases are fish sold small that were always going to become impossible.
Group size and social behaviour
Sociable and better in a small group. It is peaceful with fish of comparable size and eats smaller ones.