FishfreshwaterUndemandingHigh invasive risk

Guppy

Domestic guppies are hard-water fish, which is the opposite of what most people assume. They are also among the most widely introduced fish on Earth — released deliberately for mosquito control and now established across the tropics with documented harm to native species.

Quick profile

Scientific name: Poecilia reticulata
Adult size: 3–6 cm (1.2–2.4 in)
Lifespan: 1–3 years
Temperature: 22–28 °C (72–82 °F)
pH: 7–8.5
Hardness: 8–25 °dGH
Minimum tank: 60 L (16 US gal)
Minimum length: 60 cm
Swimming zone: Upper level
Social: Loose group — at least 6
Diet: Omnivore
Overall confidence: high confidence

What keeping this species involves

Hardy in hard alkaline water. In soft acidic water — the conditions most guppy care sheets suggest — modern strains are prone to persistent bacterial problems.

Warm, hard, often mineral-rich streams, ditches and coastal drains.

Identity and names

Common name: Guppy
Scientific name: Poecilia reticulata
Family: Poeciliidae
Order: Cyprinodontiformes
Class: Actinopterygii
Also sold as: millionfish, fancy guppy

Adult size and growth

3–6 cm (1.2–2.4 in) — Males 3–3.5 cm; females 5–6 cm and considerably bulkier.

Typical lifespan in an aquarium: 1–3 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: fusiform — the ordinary torpedo with a small terminal mouth. Assigned from what is typical of Poeciliidae, not examined for this species.

Water and tank requirements

A group of six or more with the sex ratio needed to protect females from constant pursuit.

Temperature (°C)

Guppy

22–28

Scale: 0 to 36 °C.

pH (pH)

Guppy

7–8.5

Scale: 4 to 9.5 pH.

Hardness (°dGH)

Guppy

8–25

Scale: 0 to 30 °dGH.

The bands AquariumHQ publishes for the guppy, 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

No wild referent

An animal bred in captivity for long enough that its wild habitat no longer describes the stock in the shops.

The published band describes farmed stock, not a river. That is the honest thing for it to describe, and it means wild-habitat figures for the species are interesting history rather than husbandry.

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.

TemperatureDescribes farmed stock, not a wild habitat: This animal is not sold as a wild-caught fish and has not been for a very long time. The band describes the water commercial stock is bred and raised in, which is the useful thing for it to describe; the wild population's water is a separate question and is not what a keeper is buying. 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.
pHDescribes farmed stock, not a wild habitat: This animal is not sold as a wild-caught fish and has not been for a very long time. The band describes the water commercial stock is bred and raised in, which is the useful thing for it to describe; the wild population's water is a separate question and is not what a keeper is buying. 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.
General hardnessDescribes farmed stock, not a wild habitat: This animal is not sold as a wild-caught fish and has not been for a very long time. The band describes the water commercial stock is bred and raised in, which is the useful thing for it to describe; the wild population's water is a separate question and is not what a keeper is buying. 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.

Requirement	Value	Notes
Temperature	22–28 °C (72–82 °F)	Stability matters more than hitting an exact figure.
pH	7–8.5	A stable pH outside the ideal band is usually better than an unstable one inside it.
General hardness	8–25 °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	A group of six or more with the sex ratio needed to protect females from constant pursuit.
Water flow	low	Match the outflow to this rather than to the filter's rating.
Lid required	Recommended	Reduces evaporation and prevents accidents.

Behaviour

Males pursue females almost continuously; the sex ratio is a welfare matter rather than a preference.
Fancy strains with large trailing tails swim poorly and are prime targets for fin-nippers.

Telling males from females

Males are small, colourful, with a modified anal fin (gonopodium). Females are larger and plainer.

Feeding

Diet type: Omnivore
Staples: Small dry foods, Frozen daphnia and brine shrimp, Blanched vegetable matter

Breeding

Strategy: Livebearing; females store sperm and produce successive broods
Difficulty: incidental
Parental care: bearer

A female bought from a shop is almost always already gravid and can produce several broods from one mating.

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	none	Cover reduces losses but rarely prevents them where the risk is high.
Shrimplets	moderate	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.

Assessed pairings

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.

Heavily line-bred strains are less robust than feeder-grade or wild-type stock.
Breeds without intervention. Plan for the fry before buying mixed sexes, not afterwards.

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: Native to north-eastern South America and nearby islands — Venezuela, Guyana, Trinidad, Barbados
Habitat: Warm, hard, often mineral-rich streams, ditches and coastal drains.

What the checklists say

144 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	1	A checklist states the species occurs here naturally.
Introduced	123	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	20	The source records the species as present and does not say whether it is native or introduced. AquariumHQ does not fill that in.

Legal status and responsible practice

Restriction note

Widely introduced worldwide, with established populations on every continent except Antarctica. Some jurisdictions restrict the release or transport of established non-native fish, so check the local position before moving or rehoming stock. Never release, and never dispose of unwanted fry into a watercourse or drain.

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.

Western United States and Hawaii

Locally established

Most introductions are probably fish farm or aquarium releases. Some California introductions were made intentionally, for mosquito control.

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.
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

Competition with native speciesReported in the literatureConsidered a threat to native cyprinids and killifishes, and implicated in adverse effects on the White River springfish in a Nevada spring and in the decline of the Utah sucker in a Wyoming thermal spring. Two subspecies of that springfish are now federally endangered.USGS Nonindigenous Aquatic Species database credits: Sigler and Sigler 1987; Deacon et al. 1964; Courtenay et al. 1987
Carries parasites or pathogensReported in the literatureA known carrier of certain exotic trematode parasites.

The guppy establishes in warm springs, which are small, isolated and full of endemics. A three-centimetre fish is not a small ecological event when the water body is a single spring.

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 20 countries, first in Hungary in 1924

Locally established

Biological control again, alongside angling, other intentional release and the aquarium trade — none of the four flagged. The 1924 Hungarian record is a mosquito-control introduction. Modern European guppy populations are largely confined to thermally polluted water and geothermal outflows, because the fish cannot survive a European winter.

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.
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.

What has been established

Competition with native speciesReported in the literatureRated HIGH against nature protection and restoration and HIGH against aquaculture, though the European populations are small and thermally constrained. The high ratings reflect the guppy's record in warmer parts of the world rather than what it does in Hungary.
Carries parasites or pathogensReported in the literatureRated HIGH against animal health. Guppies are a well-known carrier of Gyrodactylus and of the microsporidian Pleistophora, and a fish moved worldwide by the ornamental trade carries its parasites the same distance.

Where a tropical fish can only persist in warm discharge, the invasion risk is a function of the discharge rather than of the fish. That is a useful thing for a keeper in a cold climate to know, and it does not extend to a keeper in a warm one.

EASIN — European Alien Species Information Network · EASIN catalogue record R11898 (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.

EU

Not verified by AquariumHQpossession

No restriction was identified in the sources AquariumHQ checked for the EU as of 2026-08-11. That is not a finding that keeping, selling or moving this species is lawful there: sub-national rules, permit regimes and trade-specific requirements exist that these sources do not cover, and lists are amended. Check with the relevant authority before acquiring, selling or moving any animal.

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.

GB

Not verified by AquariumHQpossession

No restriction was identified in the sources AquariumHQ checked for Great Britain as of 2026-08-11. That is not a finding that keeping, selling or moving this species is lawful there: sub-national rules, permit regimes and trade-specific requirements exist that these sources do not cover, and lists are amended. Check with the relevant authority before acquiring, selling or moving any animal.

GB

Prohibitedrelease

Release of any non-native animal is an offence regardless of how harmless the species appears or how unlikely establishment is.

Instrument: Wildlife and Countryside Act 1981, section 14

AU

Prohibitedrelease

Guppies are established in Australian waterways and are treated as a pest in several jurisdictions. A species being ubiquitous in the trade tells you nothing about whether releasing it is lawful.

Instrument: State and territory noxious-fish and biosecurity legislation

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	Poecilia reticulata	Observed / measured	high confidence	Catalogue of Life; GBIF — Global Biodiversity Information Facility
native range	Native to north-eastern South America and nearby islands — Venezuela, Guyana, Trinidad, Barbados	Observed / measured	moderate confidence	GBIF — Global Biodiversity Information Facility
adult size	3–6 cm	Aquarium-literature consensus	high confidence	AquariumHQ husbandry synthesis
lifespan	1–3 years	Aquarium-literature consensus	high confidence	AquariumHQ husbandry synthesis
temperature	22–28 °C	Aquarium-literature consensus	high confidence	AquariumHQ husbandry synthesis
ph	7–8.5 pH	Aquarium-literature consensus	high confidence	AquariumHQ husbandry synthesis
general hardness	8–25 °dGH	Aquarium-literature consensus	high 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	≥ 6	AquariumHQ editorial position	high 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 2026-08-11. 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. 144 distribution statements held from GBIF checklists — native in 1, introduced in 118 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 sizeIndependently verifiedConfirmed by more than one independent source.2 citations, 2 independent origins

2 citations from 2 independent origins.

6 cm — FishBase · Maximum recorded · The range the species is recorded from · checked 2026-08-11
6 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. 2 independent origins.

What would improve this: Nothing. Recheck when the sources are next reviewed.

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: aquarien-atlas.

18–28 °C — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11

What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. Derived from the observed range rather than copied from it. The observed envelope spans conditions this species meets across seasons and localities; a keeper holds one temperature continuously. The advised band trims the lower end because sustained residence at an extreme is a different demand from encountering it, and stability matters more to a captive fish than breadth.

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

phIndependently verifiedConfirmed by more than one independent source.2 citations, 2 independent origins

2 citations from 2 independent origins.

7–8.2 pH — AquariumHQ husbandry synthesis · Recommended for keeping · Recommended for keeping · checked 2026-08-11
7–8 pH — Ornamental Aquatic Trade Association · Recommended for keeping · Recommended for keeping · checked 2026-08-11Corrected on checking from 6.8–8 pH.
7–8 pH — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11

What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. 2 independent origins.

What would improve this: Nothing. Recheck when the sources are next reviewed.

general hardnessIndependently verifiedConfirmed by more than one independent source.2 citations, 2 independent origins

2 citations from 2 independent origins.

10–25 °dGH — AquariumHQ husbandry synthesis · Recommended for keeping · Recommended for keeping · checked 2026-08-11
9–19 °dGH — FishBase · Tolerated range · The range the species is recorded from · checked 2026-08-11Corrected on checking from 5–30 °dGH.
8–18 °dGH — Ornamental Aquatic Trade Association · Recommended for keeping · Recommended for keeping · checked 2026-08-11Corrected on checking from 8–20 °dGH.

What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. 2 independent origins.

What would improve this: Nothing. Recheck when the sources are next reviewed.

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.
How aquarium species get into the wildThis species has a documented introduction outside its native range, with the route recorded.
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.
How to read a compatibility verdictThis animal's fins are a target, and most compatibility verdicts about that are derived rather than observed.

Guppy

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

Assessed pairings

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

Western United States and Hawaii

What has been established

Europe — recorded in 20 countries, first in Hungary in 1924

What has been established

EU

GB

GB

AU

Evidence

Why we say this

Guides relevant to this species