FishfreshwaterDemandingHigh invasive risk

Walking catfish

An air-breathing catfish that can cross land between water bodies using its pectoral spines, and which became one of the most notorious aquarium-trade introductions in North America. It is hardy to an extraordinary degree and is a predator of everything smaller than itself.

Quick profile

Scientific name: Clarias batrachus
Adult size: 30–47 cm (11.8–18.5 in)
Lifespan: 8–12 years
Temperature: 20–30 °C (68–86 °F)
pH: 6–8
Hardness: 3–20 °dGH
Minimum tank: 400 L (106 US gal)
Minimum length: 180 cm
Swimming zone: Bottom
Social: Solitary
Diet: Omnivore
Overall confidence: moderate confidence

A walking catfish resting on sand, showing the elongated body, the long barbels around the mouth and the pale patch on the flank. — Vassil · Wikimedia Commons · CC0Identified as *Clarias batrachus* from its source categorisation and reviewed by eye. AquariumHQ publishes no generated imagery of any organism.

What keeping this species involves

Almost impossible to kill and almost impossible to house responsibly. It reaches half a metre, breathes air, climbs out of tanks and eats its tankmates.

Swamps, ditches, rice paddies and stagnant pools, including water too low in oxygen for most fish, which it survives by breathing air.

Identity and names

Common name: Walking catfish
Scientific name: Clarias batrachus
Family: Clariidae
Order: Siluriformes
Class: Actinopterygii
Also sold as: Clarias batrachus, clarias, magur, albino walking catfish

Adult size and growth

30–47 cm (11.8–18.5 in)

Typical lifespan in an aquarium: 8–12 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: eel-like with a large — a piscivore's mouth. A broad flat mouth on an eel-like body — it is both wide-gaped and slender, which the family default catches and the length rule did not.

Water and tank requirements

A fish approaching half a metre that must reach the surface to breathe and will leave the tank if it can. Floor area and a sealed lid are both requirements.

Temperature (°C)

Walking catfish

20–30

Scale: 0 to 36 °C.

pH (pH)

Walking catfish

6–8

Scale: 4 to 9.5 pH.

Hardness (°dGH)

Walking catfish

3–20

Scale: 0 to 30 °dGH.

The bands AquariumHQ publishes for the walking catfish, each drawn against the full range this catalogue uses for that parameter. A narrow band on a wide scale is a specialist; a wide one is a genuinely tolerant animal. Source: AquariumHQ husbandry position for this record — an editorial range, not a measurement

Why these ranges: A species found in water that would kill most fish, from cool ditches to warm stagnant paddies. The wide band is a documented tolerance and it is not an invitation to test the limits.

Where these figures come from

Habitat class

Rice paddy, ditch and drain

Shallow, still, sun-warmed managed water — agricultural rather than natural, and now the primary habitat of a number of aquarium species.

Enormous daily and annual temperature swing, low oxygen and shallow water. Species from here tolerate far more than a tropical community setting suggests, and several of them do not want to be kept at 26 °C all year.

Conductivity: 80–500 µS/cm
Flow: still
Dissolved oxygen: low
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	20–30 °C (68–86 °F)	Stability matters more than hitting an exact figure.
pH	6–8	A stable pH outside the ideal band is usually better than an unstable one inside it.
General hardness	3–20 °dGH	Check your supplier's published figure before choosing species.
Minimum volume	400 L (106 US gal)	A floor, not a recommendation.
Minimum footprint	180 cm long × 50 cm deep	A fish approaching half a metre that must reach the surface to breathe and will leave the tank if it can. Floor area and a sealed lid are both requirements.
Water flow	low	Match the outflow to this rather than to the filter's rating.
Lid required	Yes	This species jumps.
Structure	Open floor with large caves and a securely weighted lid. Access to the surface is a physiological requirement rather than a preference.

Behaviour

Uses the stiffened pectoral spines to lever itself forward over damp ground, which is how it moves between pools and how it leaves aquaria.
Breathes atmospheric air through a paired arborescent organ above the gills, so it must be able to reach the surface at all times.

Telling males from females

Males have a more pointed genital papilla and are slimmer in condition. Not readable in juveniles.

Feeding

An indiscriminate omnivore that eats fish, invertebrates, plant material and carrion. It is very easily overfed and grows accordingly.

Diet type: Omnivore
Staples: Large sinking pellets, Prawn, Mussel, Earthworm
Avoid: Live feeder fish, Mammalian meat

Breeding

Strategy: Eggs laid in an excavated nest and guarded by the parents
Difficulty: challenging
Parental care: guarding

Farmed at scale across Asia as a food fish. Aquarium spawning is uncommon and the fry are cannibalistic.

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.

Risk this species poses to common tankmates
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.

The albino form is the one usually sold and is the same animal. Its adult size is not smaller and its temperament is not milder.
Established and invasive in Florida following escapes from aquaculture facilities in the 1960s, and it is restricted or prohibited in a number of jurisdictions as a result.

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: South and South-East Asia natively; introduced and invasive in Florida and elsewhere
Habitat: Swamps, ditches, rice paddies and stagnant pools, including water too low in oxygen for most fish, which it survives by breathing air.

What the checklists say

40 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	30	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	10	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

Restriction note

Prohibited or restricted in a number of jurisdictions including several US states, where it is listed as an injurious or prohibited species. The specific rules differ substantially between them and between countries; check the position that applies rather than generalising from the Florida listing.

Where this species has been introduced, and what followed

Two databases on two continents hold records for this species, and they are not two accounts of one event. They are separate introductions with separate causes, and the differences between them are the most informative thing on this panel.

Florida

Established

Imported to Florida from Thailand in the early 1960s for the aquarium trade. The first introductions occurred in the mid-1960s when adult brood stock escaped from a fish farm or from a truck transporting brood fish between counties, with additional purposeful releases by fish farmers afterwards.

Escape from an ornamental fish farmOrnamental fish farms are usually outdoor ponds in warm places, and warm places are where tropical species establish. Several of the best-known Florida introductions began this way rather than with a keeper.
Deliberate aquarium releaseSomebody took the animal out of a tank and put it into open water. The commonest reason is that the fish outgrew the aquarium, which is why size at maturity is a conservation question as well as a welfare one.
Spread from an existing introduced populationMovement along connected water from a population already established. This is why a single introduction is not a single event.

What has been established

Predation on native speciesReported in the literatureInvades aquaculture ponds and preys on fish stocks, to the point that farmers erected protective fences. Heavy predation on native fishes was reported in remnant pools during seasonal drying of wetlands.USGS Nonindigenous Aquatic Species database credits: Courtenay and Stauffer 1990; Loftus 1988
Predation on native speciesMeasured in studyIn a study of tadpole assemblages in temporary Florida wetlands, NATIVE fishes had larger impacts and higher predation rates on tadpoles than the walking catfish did. A measured result that runs against the expectation.USGS Nonindigenous Aquatic Species database credits: Baber and Babbitt 2003

An air-breathing catfish that moves overland between water bodies. Containment failures at a facility are not recoverable, which is why the escape route mattered more than the release route here.

USGS Nonindigenous Aquatic Species database · Species Profile — Means of Introduction; Species Profile — Impact of Introduction · read 2026-08-29. A United States database: the routes and effects recorded here are the ones documented there, and say nothing about other regions.

Europe — United Kingdom from 2009, also Italy

Recorded, not established

Angling, flagged LOW uncertainty. Two countries and a 2009 first record — a marginal European presence for a species that is thoroughly established in Florida, where AquariumHQ's other record for it comes from.

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

Carries parasites or pathogensReported in the literatureRated HIGH against animal health and MEDIUM against aquaculture. The ratings are drawn from the species' record elsewhere rather than from European observation.

EASIN — European Alien Species Information Network · EASIN catalogue record R03727 (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.

What AquariumHQ has recorded, by jurisdiction, with the instrument each entry comes from and how far the check went. Ecological risk and legal status are separate: a species can be ecologically risky and legally unrestricted, or restricted where it could never establish.

US

Prohibitedimport

The listing is drawn at FAMILY level — 'live fish or viable eggs of walking catfish, family Clariidae' — so it covers every clariid rather than only the species that prompted it. Importation, transportation and acquisition are prohibited.

Instrument: 50 CFR § 16.13(a)(2)(i), injurious wildlife listing under 18 U.S.C. 42

The family-level scope is the detail aquarists miss. Any Clarias, and every other clariid genus, is inside this listing whatever the shop label says. State law frequently adds a possession prohibition that the federal instrument does not contain.

Checked against the instrument · last checked 2026-08-29 · An editor has read the current text of the named instrument and confirmed this species' entry on the date shown.

EU

Not verified by AquariumHQpossession

The consolidated Union list was read in full on 2026-08-29 and contains no Clarias or Clariidae entry. No restriction was identified in that instrument. That is not a finding that keeping this species is lawful in the EU: member states legislate separately, the species is farmed in several of them, and schedules are amended. Check with the relevant authority before acquiring, selling or moving any animal.

Instrument: Commission Implementing Regulation (EU) 2016/1141 (consolidated text 02016R1141-20220802)

Checked against the instrument · last checked 2026-08-29 · An editor has read the current text of the named instrument and confirmed this species' entry on the date shown.

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	Clarias batrachus	Observed / measured	high confidence	Catalogue of Life; GBIF — Global Biodiversity Information Facility
native range	South and South-East Asia natively; introduced and invasive in Florida and elsewhere	Observed / measured	moderate confidence	GBIF — Global Biodiversity Information Facility
adult size	30–47 cm	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
lifespan	8–12 years	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
temperature	20–30 °C	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
ph	6–8 pH	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
general hardness	3–20 °dGH	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
minimum tank volume	≥ 400 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. 40 distribution statements held from GBIF checklists — introduced in 30 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 sizeOne sourceAquariumHQ's own position, derived from evidenced inputs.1 citation, 1 independent origin

A single source: usgs-nas.

61 cm — USGS Nonindigenous Aquatic Species database · Maximum recorded · Observed in the wild · checked 2026-08-29

What this kind of claim needs: size a well-kept specimen reaches — no external source is required, provided AquariumHQ shows its reasoning. A documented maximum is held and the catalogue's typical adult range is stated separately, with the relationship between them recorded rather than collapsed. A well-grown adult may be substantially larger than the typical figure — 61 cm TL against a typical 30–47 cm. Large enough to change what tank is appropriate.

What would improve this: Corroborate against a second, independent source.

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 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 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 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 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.

Predator and prey sizeIt takes fish that fit in its mouth, and its mouth grows with it.
Territorial behaviourIt defends ground, and the shape of what it defends decides the tank more than the volume does.
Native, introduced and invasiveThis record carries an invasive or legal note, and those are five separate claims that are easy to read as one.
Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
Why fish size figures disagreeThe largest recorded specimen is far enough above the typical adult here to change what tank is appropriate.
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 47 cm. Most of the difficult rehoming cases are fish sold small that were always going to become impossible.
What a legal restriction on a species actually meansAquariumHQ holds a structured legal status for this species, and possession, sale, import and release are four separate questions.

Walking catfish

Quick profile

What keeping this species involves

Identity and names

Adult size and growth

Water and tank requirements

Where these figures come from

Group size and social behaviour

Behaviour

Telling males from females

Feeding

Breeding

Tankmates and compatibility

Welfare considerations

Problems to watch for

Where it comes from

What the checklists say

Legal status and responsible practice

Where this species has been introduced, and what followed

Florida

What has been established

Europe — United Kingdom from 2009, also Italy

What has been established

US

EU

Evidence

Why we say this

Guides relevant to this species