Other invertebratefreshwaterSpecialist

Zebra mussel

A small striped mussel that attaches to hard surfaces with byssal threads and forms dense encrusting beds, blocking water pipes and smothering native mussels. It is among the most economically damaging freshwater invaders and is prohibited in many jurisdictions.

Quick profile

Scientific name: Dreissena polymorpha
Adult size: 2–4 cm (0.8–1.6 in)
Lifespan: 2–5 years
Temperature: 4–28 °C (39–82 °F)
pH: 7.2–8.6
Hardness: 10–30 °dGH
Minimum tank: 40 L (11 US gal)
Minimum length: 50 cm
Swimming zone: Bottom
Social: Tolerant of any grouping
Diet: Filter feeder
Overall confidence: moderate confidence

What keeping this species involves

An obligate filter feeder that starves in a clean tank, and a prohibited species in most of Europe and much of North America. Neither problem has a husbandry solution.

Hard surfaces in lakes, rivers and canals — rock, wood, pipework and other molluscs — in cool hard water.

Identity and names

Common name: Zebra mussel
Scientific name: Dreissena polymorpha
Family: Dreissenidae
Order: Myida
Class: Bivalvia
Also sold as: Dreissena polymorpha, striped mussel, wandering mussel

Adult size and growth

2–4 cm (0.8–1.6 in)

Typical lifespan in an aquarium: 2–5 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 grazing or sucking mouth. Assigned from what is typical of Dreissenidae, not examined for this species.

Water and tank requirements

Recorded for completeness. This is a species AquariumHQ does not recommend keeping, and in most of the jurisdictions this catalogue serves it is prohibited.

Temperature (°C)

Zebra mussel

4–28

Scale: 0 to 36 °C.

pH (pH)

Zebra mussel

7.2–8.6

Scale: 4 to 9.5 pH.

Hardness (°dGH)

Zebra mussel

10–30

Scale: 0 to 30 °dGH.

The bands AquariumHQ publishes for the zebra mussel, 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: Cool to warm temperate hard water. Calcium is the parameter that limits where this species can establish, which is why hard-water systems are the ones at risk and soft-water ones largely are not.

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.

TemperatureReasoned on this record: This record states its own reason for this band. See the water section. 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.
pHReasoned on this record: This record states its own reason for this band. See the water section.
General hardnessSet by a requirement of the animal: Hardness here is a shell requirement, not a habitat statement. A snail or mussel builds and repairs aragonite continuously, and in water without dissolved calcium the shell erodes faster than the animal can replace it — visibly, at the apex first. The band is therefore set by what the animal has to take out of the water rather than by what its river happens to contain, and several of these species are recorded from water considerably softer than the band advises.

Requirement	Value	Notes
Temperature	4–28 °C (39–82 °F)	Stability matters more than hitting an exact figure.
pH	7.2–8.6	A stable pH outside the ideal band is usually better than an unstable one inside it.
General hardness	10–30 °dGH	Check your supplier's published figure before choosing species.
Minimum volume	40 L (11 US gal)	A floor, not a recommendation.
Minimum footprint	50 cm long × 30 cm deep	Recorded for completeness. This is a species AquariumHQ does not recommend keeping, and in most of the jurisdictions this catalogue serves it is prohibited.
Water flow	moderate	Match the outflow to this rather than to the filter's rating.
Lid required	Recommended	Reduces evaporation and prevents accidents.
Structure	Hard surfaces to attach to and a continuous supply of suspended food.

Behaviour

Attaches to any hard surface with byssal threads, including the shells of living native mussels, which it smothers.
Filters large volumes of water and strips phytoplankton, which changes the clarity and the food web of an invaded lake measurably.

Telling males from females

Sexes are separate and are not distinguishable externally.

Feeding

An obligate suspension feeder that filters phytoplankton continuously. In a clean aquarium there is nothing for it to eat, and it starves slowly.

Diet type: Filter feeder
Staples: Suspended phytoplankton, Fine suspended particles

Breeding

Strategy: Free-swimming veliger larvae released into the water column
Difficulty: rarely achieved
Parental care: none

The planktonic larval stage is what makes this species so mobile: larvae travel with water and are invisible in a bucket.

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	none	Determines whether a shrimp colony can grow rather than merely persist.
Snails	none	Applies to snails you wanted as well as snails you did not.
Long or trailing fins	none	Fin damage is an entry point for secondary infection.
Plants	none	Tough species such as Anubias and Java fern survive most grazers.

Any pair in the catalogue can be assessed with the compatibility checker.

Welfare considerations

Points where the way this species is commonly sold or kept differs from what it actually needs.

Spread principally by boats, equipment and water transfer rather than by the aquarium trade, though larvae travel in any transported water.
Never move water, plants or equipment between an aquarium and a natural water body. The larvae are microscopic and a bucket is enough.

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 the Black and Caspian Sea basins; introduced across Europe and North America
Habitat: Hard surfaces in lakes, rivers and canals — rock, wood, pipework and other molluscs — in cool hard water.

What the checklists say

80 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	65	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	14	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 subject to strict control in many jurisdictions, including a number of US states and Canadian provinces where transport of water and equipment is separately regulated. Rules on invasive bivalves are usually framed around movement and equipment rather than around ownership; check the local position.

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.

North America

Established

A release of larval mussels during the ballast exchange of a single commercial cargo ship travelling from the northern Black Sea to the Great Lakes has been deduced as the likely vector. Its rapid dispersal followed from the free-floating veliger stage and from attachment to boats.

Ballast water or hull foulingLarvae carried in a ship's ballast tanks and discharged in another continent's fresh water. Nothing to do with aquariums, and the route behind two of the most consequential freshwater invasions on record.
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

Biofouling of pipes and structuresMeasured in studyColonises water supply pipes of hydroelectric and nuclear power plants, public water plants and industrial facilities, constricting flow. Densities reached 700,000 per square metre at one Michigan power plant, and pipe diameters have been reduced by two thirds at water treatment facilities.

One introduction event, from one ship, from which everything else followed. Nothing to do with the aquarium trade, and included here because the contrast is the point: the two most consequential freshwater invasions in North America arrived in ballast tanks.

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 38 countries, first in Lithuania in 1803

Established

Six pathways, dominated by shipping: ballast water, hull fouling and hitchhiking on boats. The pet and aquarium route is listed and it is not the story. The 1803 Lithuanian record makes this the oldest first-introduction date in the batch, and the invasion followed the canal network out of the Ponto-Caspian basin two centuries before anyone kept a planted tank.

Ballast water or hull foulingLarvae carried in a ship's ballast tanks and discharged in another continent's fresh water. Nothing to do with aquariums, and the route behind two of the most consequential freshwater invasions on record.
Arrived with a shipment of something elseThe organism was not the thing being shipped. Snails on aquarium plants, clams in shellfish consignments, apple snails in farmed crayfish.
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

Biofouling of pipes and structuresMeasured in studyEASIN records an impact and scores no sector, which understates a case that is exceptionally well studied elsewhere. AquariumHQ holds a USGS NAS record covering the North American invasion, where the biofouling and filtration effects are measured; the European record here adds the two-century head start and the canal pathway.

Never sold as an aquarium animal. It appears in this catalogue because it is the reference case for what a filter-feeding bivalve does to a water body, and because it arrives on boats and equipment rather than in bags.

EASIN — European Alien Species Information Network · EASIN catalogue record R05292 (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 covers live mollusks, veligers or viable eggs of zebra mussels at genus level — 'genus Dreissena' — so it catches the quagga mussel as well. The prohibition is on importation, transportation and acquisition.

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

The veliger clause is the one that matters to anybody moving water. Larvae are microscopic and travel in a bucket, which is why state-level rules in North America regulate the movement of water and equipment rather than only the animal.

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 entry for Dreissena. No restriction was identified in that instrument. That is not a finding that keeping this species is lawful in the EU: the Union list is a list of species whose spread the Union is trying to prevent, and a species already established across the continent is a poor candidate for it. Member States legislate separately and have not been checked here.

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

Absence from the Union list is the clearest illustration in this file of why a negative finding is not a permission. This is one of the most damaging freshwater invaders in Europe and it is not listed, because listing is forward-looking and the species arrived two centuries ago.

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.

GB

Prohibitedrelease

Release or escape of any non-native animal is an offence. For this species the duty is practical rather than theoretical: larvae travel in transported water, so emptying a tank into a drain that reaches open water is the mechanism to avoid.

Instrument: Wildlife and Countryside Act 1981, section 14

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.

JP

Permit requiredpossession

Dreissena polymorpha is designated by name on the Ministry's list, alongside D. bugensis and the whole of the genus Limnoperna. A keeping permit under the Act may be granted for academic research, exhibition, education and similar purposes. The Ministry states directly that keeping as a pet is not among them, so for an aquarist the practical effect of “permit required” is prohibition.

Instrument: Act on the Prevention of Adverse Ecological Effects Caused by Designated Invasive Alien Species (Act No. 78 of 2004), as amended 2022 — designated invasive alien species, Dreissena polymorpha

Unlike the crayfish entries this one is at species level, which is why it is recorded separately rather than generated from a family rule.

Checked against the instrument · last checked 2026-08-30 · An editor has read the current text of the named instrument and confirmed this species' entry on the date shown.

JP

Prohibitedrelease

Release into the wild is prohibited. Zebra mussel larvae are microscopic and travel in transferred water, so the practical risk from an aquarium is water disposal rather than a deliberate release of adults.

Checked against the instrument · last checked 2026-08-30 · 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	Dreissena polymorpha	Observed / measured	high confidence	Catalogue of Life; GBIF — Global Biodiversity Information Facility
native range	Native to the Black and Caspian Sea basins; introduced across Europe and North America	Observed / measured	moderate confidence	GBIF — Global Biodiversity Information Facility
adult size	2–4 cm	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
lifespan	2–5 years	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
temperature	4–28 °C	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
ph	7.2–8.6 pH	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
general hardness	10–30 °dGH	Aquarium-literature consensus	moderate confidence	AquariumHQ husbandry synthesis
minimum tank volume	≥ 40 L	AquariumHQ editorial position	moderate confidence	AquariumHQ husbandry synthesis
minimum tank length	≥ 50 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. 80 distribution statements held from GBIF checklists — introduced in 52, 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 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.

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

A single source: McMahon 1996.

12–22 °C — USGS Nonindigenous Aquatic Species database · Conditions for breeding · 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. This record states its own reason for this band. See the water section. 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.

Guides relevant to this species

Chosen from this record's own traits rather than listed on every page.

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.
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.

Zebra mussel

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

North America

What has been established

Europe — recorded in 38 countries, first in Lithuania in 1803

What has been established

US

EU

GB

JP

JP

Evidence

Why we say this

Guides relevant to this species