FishfreshwaterModerateHigh invasive risk

Weather loach

A temperate, 25 cm, air-breathing loach that reacts visibly to falling barometric pressure — hence the name. Sold as a tropical community fish, which it is not, and established as a damaging invader in several countries.

Quick profile

Scientific name: Misgurnus anguillicaudatus
Adult size: 20–28 cm (7.9–11 in)
Lifespan: 7–10 years
Temperature: 5–22 °C (41–72 °F)
pH: 6.5–8
Hardness: 5–20 °dGH
Minimum tank: 250 L (66 US gal)
Minimum length: 120 cm
Swimming zone: Bottom
Social: Loose group — at least 3
Diet: Omnivore
Overall confidence: moderate confidence

A weather loach on blue substrate beside a paler individual, the elongated body and the ring of barbels around the downturned mouth clearly visible. — Gourami Watcher · Wikimedia Commons · CC BY-SA 3.0 · share-alikeIdentified as *Misgurnus anguillicaudatus* from its source categorisation and reviewed by eye. AquariumHQ publishes no generated imagery of any organism.

What keeping this species involves

Extremely hardy, but temperate rather than tropical and much larger than it is sold as.

Muddy-bottomed ponds, paddies and slow rivers; survives in low-oxygen water by gulping air.

Identity and names

Common name: Weather loach
Scientific name: Misgurnus anguillicaudatus
Family: Cobitidae
Order: Cypriniformes
Class: Actinopterygii
Also sold as: dojo loach, pond loach

Adult size and growth

20–28 cm (7.9–11 in)

Typical lifespan in an aquarium: 7–10 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 small terminal mouth. Assigned from what is typical of Cobitidae, not examined for this species.

Water and tank requirements

A 25 cm bottom-dwelling fish kept in a group, needing floor area rather than depth.

Temperature (°C)

Weather loach

5–22

Scale: 0 to 36 °C.

pH (pH)

Weather loach

6.5–8

Scale: 4 to 9.5 pH.

Hardness (°dGH)

Weather loach

5–20

Scale: 0 to 30 °dGH.

The bands AquariumHQ publishes for the weather loach, 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

Where these figures come from

Habitat class

Temperate still water

Ponds, lakes, canals and slow rivers outside the tropics, with a genuine winter.

The temperature range is the point. These animals experience a seasonal cycle, and keeping them at a constant tropical temperature shortens their lives without ever looking like the cause.

Conductivity: 150–800 µS/cm
Flow: still
Dissolved oxygen: variable
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.

TemperatureFollows the habitat this animal comes from: Follows the water this animal is recorded from — temperate still water. Temperate still water generally runs 2–28°C, and the advised band of 5–22°C is consistent with it. This is AquariumHQ's reasoning from the habitat, not a measurement of the species. A source does publish a figure for this parameter, and it answers a different question — an environmental range or a laboratory tolerance rather than a keeping recommendation. It is held alongside this band rather than behind it.
pHFollows the habitat this animal comes from: Follows the water this animal is recorded from — temperate still water. Temperate still water generally runs 6.5–8.2, and the advised band of 6.5–8 is consistent with it. This is AquariumHQ's reasoning from the habitat, not a measurement of the species.
General hardnessFollows the habitat this animal comes from: Follows the water this animal is recorded from — temperate still water. Temperate still water generally runs 4–20 dGH, and the advised band of 5–20 dGH is consistent with it. This is AquariumHQ's reasoning from the habitat, not a measurement of the species.

AquariumHQ advises

5–22

The habitatTemperate still water

2–28

Scale: -1.9 to 31.9 °C.

Temperature: AquariumHQ's advised band against the habitat it is drawn from. Source: AquariumHQ advised range; habitat envelope is AquariumHQ's summary of the general limnology for this class of water body.

AquariumHQ advises

6.5–8

The habitatTemperate still water

6.5–8.2

Scale: 6.2 to 8.5 pH.

pH: AquariumHQ's advised band against the habitat it is drawn from. Source: AquariumHQ advised range; habitat envelope is AquariumHQ's summary of the general limnology for this class of water body.

AquariumHQ advises

5–20

The habitatTemperate still water

4–20

Scale: 1.6 to 22.4 dGH.

General hardness: AquariumHQ's advised band against the habitat it is drawn from. Source: AquariumHQ advised range; habitat envelope is AquariumHQ's summary of the general limnology for this class of water body.

Requirement	Value	Notes
Temperature	5–22 °C (41–72 °F)	Stability matters more than hitting an exact figure.
pH	6.5–8	A stable pH outside the ideal band is usually better than an unstable one inside it.
General hardness	5–20 °dGH	Check your supplier's published figure before choosing species.
Minimum volume	250 L (66 US gal)	A floor, not a recommendation.
Minimum footprint	120 cm long	A 25 cm bottom-dwelling fish kept in a group, needing floor area rather than depth.
Water flow	moderate	Match the outflow to this rather than to the filter's rating.
Lid required	Yes	This species jumps.
Structure	Soft sand deep enough to burrow into, plus cover.

Behaviour

Becomes agitated before weather changes — a genuine and well-documented response to pressure.
Gulps air at the surface and absorbs oxygen through the gut.
Escapes through the smallest gap.

Feeding

Diet type: Omnivore
Staples: Sinking pellets, Frozen bloodworm, Blanched vegetables, Snails

Breeding

Strategy: Seasonal egg-scattering
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.

Risk this species poses to common tankmates
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	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	high	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.

Best kept in an unheated tank or an outdoor pond in a temperate climate.
Listed as an invasive species in several countries; never release.

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: East Asia — China, Korea, Japan, Russia; widely introduced elsewhere
Habitat: Muddy-bottomed ponds, paddies and slow rivers; survives in low-oxygen water by gulping air.

What the checklists say

39 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	26	A checklist states the species arrived here with human help. That is not a statement that it is established, harmful or illegal.
Recorded as invasive	1	A checklist states the species is invasive here. AquariumHQ reproduces that assessment; it does not make one.
Recorded as present, establishment means not stated	12	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

Established as an introduced species in parts of North America, Europe and Australia, where it displaces native bottom-dwellers. Sale or possession is restricted in several jurisdictions. Check the position locally before acquiring, and never release.

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.

California, Michigan, Hawaii and elsewhere

Established

California populations descend from fish that escaped a goldfish farm, possibly as early as the 1930s. Michigan populations descend from fish imported from Kobe that escaped an aquarium supply company before 1951. The Hawaiian introduction was presumably by Asian immigrants during the 1800s, for food.

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 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

Predation on native speciesReported in the literatureMay reduce populations of aquatic insects important as food to native fishes.USGS Nonindigenous Aquatic Species database credits: Page and Laird 1993; USEPA 2008
Increased turbidity and disturbed sedimentMeasured in studyAustralian experimental work suggests it may significantly reduce macroinvertebrate abundance and increase turbidity and nitrogen levels in standing water.USGS Nonindigenous Aquatic Species database credits: Keller and Lake 2007

A fish that survives being frozen into ice and tolerates ammonia concentrations that would kill almost anything else. Very little about a temperate water body limits it.

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 — recorded in 10 countries, first in Germany in 1990

Established

The clearest aquarium-origin fish in the European record. EASIN records the pet and aquarium pathway twice, once flagged LOW uncertainty, alongside live bait at HIGH uncertainty, biological control, interconnected waterways and unaided spread. Low uncertainty on the aquarium route is EASIN saying it is confident, and it says that for very few species.

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.
Bait-bucket release by anglersAn angler empties an unused bait bucket at the end of a session. Documented as the primary route for several crayfish and small fish, and almost entirely absent from the aquarium hobby's account of the problem.
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

Carries parasites or pathogensReported in the literatureRated HIGH against animal health and HIGH against human health. The human-health rating reflects the species' role as an intermediate host for trematodes in its native range.
Increased turbidity and disturbed sedimentMeasured in studyRated MEDIUM against clean water. The animal feeds by working through soft sediment, and at density that keeps sediment in suspension.
Competition with native speciesReported in the literatureRated HIGH against nature protection and restoration. It tolerates low oxygen, breathes air through the gut and survives cold, which between them mean very little in a temperate waterway limits it.

Of Union concern. A common, hardy, long-lived aquarium fish that grows larger than most keepers expect and is prohibited across the EU — one of the sharpest mismatches in the catalogue between what a shop sells and what the law says.

EASIN — European Alien Species Information Network · EASIN catalogue record R09519 (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.

GB

Prohibitedrelease

A temperate-tolerant species capable of surviving British winters, which makes it one of the aquarium fish of most concern for establishment. Release is an offence and the risk here is not theoretical.

Instrument: Wildlife and Countryside Act 1981, section 14; the species is monitored by the GB Non-native Species Secretariat

Instrument recorded, species entry not re-checked · last checked 2026-08-11 · AquariumHQ has recorded the instrument and what it does, but has not re-confirmed this species' entry against the current consolidated text. Listings are amended, so treat this as a pointer to the right law rather than as a confirmation of the current position, and check with the authority before acting.

US

Restrictedpossession

Established non-native populations are recorded in several US states, and a number of states list the species as prohibited or restricted. There is no single federal position.

Instrument: State-level prohibited and restricted species lists, which vary by state

This is a species where the answer genuinely depends on the state, and a national answer would be misleading in both directions.

AU

Prohibitedimport

A cold-tolerant loach with a documented capacity to establish is not a species Australia's permitted-list regime admits.

Instrument: Environment Protection and Biodiversity Conservation Act 1999 — List of Specimens taken to be Suitable for Live Import

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	Misgurnus anguillicaudatus	Observed / measured	high confidence	Catalogue of Life; GBIF — Global Biodiversity Information Facility
native range	East Asia — China, Korea, Japan, Russia; widely introduced elsewhere	Observed / measured	moderate confidence	GBIF — Global Biodiversity Information Facility
adult size	20–28 cm	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
lifespan	7–10 years	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
temperature	5–22 °C	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
ph	6.5–8 pH	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
general hardness	5–20 °dGH	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
minimum tank volume	≥ 250 L	AquariumHQ editorial position	moderate confidence	AquariumHQ husbandry synthesis
minimum tank length	≥ 120 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 2026-08-12. 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. 39 distribution statements held from GBIF checklists — introduced in 25, recorded invasive in 1 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 sizeOne sourceBased on a verified authoritative source.1 citation, 1 independent origin

A single source: kottelat-freyhof-2007.

28 cm — USGS Nonindigenous Aquatic Species database · Maximum recorded · Observed in the wild · checked 2026-08-29
10–20 cm — USGS Nonindigenous Aquatic Species database · Typically observed · 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 source publishes a typical adult size for this species, separately from any maximum. That is the quantity this claim is about.

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.

temperatureOne sourceAquariumHQ's own position, derived from evidenced inputs.1 citation, 1 independent origin

A single source: Urquhart and Koetsier 2014a; McMahon and Burggren 1987; Rixon et al. 2005; Urquhart and Koetsier 2014b.

-2–38 °C — USGS Nonindigenous Aquatic Species database · Tolerated range · Measured under laboratory conditions · checked 2026-08-29

What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. The advised band does not rest on the observation held. Follows the water this animal is recorded from — temperate still water. Temperate still water generally runs 2–28°C, and the advised band of 5–22°C is consistent with it. This is AquariumHQ's reasoning from the habitat, not a measurement of the species. A source does publish a figure for this parameter, and it answers a different question — an environmental range or a laboratory tolerance rather than a keeping recommendation. It is held alongside this band rather than behind it.

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

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.

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.
Native, introduced and invasiveThis record carries an invasive or legal note, and those are five separate claims that are easy to read as one.
The kinds of water aquarium fish come fromThis record's water bands follow temperate still water, which is the kind of water this animal is recorded from.
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 28 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.

Weather loach

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

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

California, Michigan, Hawaii and elsewhere

What has been established

Europe — recorded in 10 countries, first in Germany in 1990

What has been established

GB

US

AU

Evidence

Why we say this

Guides relevant to this species