Three-spined stickleback
The fish most northern-hemisphere children catch in a net, and one of the most studied animals in evolutionary biology. A male in breeding condition builds a glued nest, turns red, and defends it with a display that is worth a tank on its own — for the three or four months of the year it happens.
Quick profile
- Scientific name
- Gasterosteus aculeatus
- Adult size
- 4–8 cm (1.6–3.1 in)
- Lifespan
- 1–3 years
- Temperature
- 4–20 °C (39–68 °F)
- pH
- 6.5–8.2
- Hardness
- 5–20 °dGH
- Minimum tank
- 60 L (16 US gal)
- Minimum length
- 80 cm
- Swimming zone
- All levels
- Social
- Loose group — at least 5
- Diet
- Micropredator
- Overall confidence
- moderate confidence
What keeping this species involves
Undemanding about water and demanding about temperature and food. It needs a cold season and live or frozen food, and neither is optional.
Almost any cool shallow water: ditches, streams, ponds, estuaries and the sea itself, with populations that are entirely freshwater, entirely marine and everything between.
Identity and names
- Common name
- Three-spined stickleback
- Scientific name
- Gasterosteus aculeatus
- Family
- Gasterosteidae
- Order
- Perciformes
- Class
- Actinopterygii
- Also sold as
- stickleback, tiddler, Gasterosteus aculeatus, common stickleback
Adult size and growth
4–8 cm (1.6–3.1 in) — Freshwater populations run smaller than anadromous ones. The armour plating varies between populations too, and is the character the evolutionary work turns on.
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 Gasterosteidae, not examined for this species.
Water and tank requirements
A nesting male holds a floor territory and drives everything off it, so the tank needs a defended patch plus somewhere for the others to be — length rather than volume.
Temperature (°C)
Scale: 0 to 36 °C.
pH (pH)
Scale: 4 to 9.5 pH.
Hardness (°dGH)
Scale: 0 to 30 °dGH.
Why these ranges: A temperate species with a genuine winter, and the band is the annual span of the water it lives in rather than a setting to hold. Kept at a constant tropical temperature it lives about a year; kept with a cold season it breeds and lives longer. The width of this band is the point of it.
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.
- 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 | 4–20 °C (39–68 °F) | Stability matters more than hitting an exact figure. |
| pH | 6.5–8.2 | 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 | 60 L (16 US gal) | A floor, not a recommendation. |
| Minimum footprint | 80 cm long | A nesting male holds a floor territory and drives everything off it, so the tank needs a defended patch plus somewhere for the others to be — length rather than volume. |
| Water flow | low | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Fine sand, dense marginal planting and open floor for a nest site. |
Behaviour
- The male's nest-building and zig-zag courtship display are among the best-described behaviours in any fish and happen readily in a tank.
- Takes small invertebrates continuously and will strip a shrimp colony.
Telling males from females
Breeding males develop a red throat and blue eyes and are unmistakable. Outside the season the sexes are hard to tell apart.
Feeding
Takes almost no dry food. This is the practical reason it is difficult in a general community tank rather than any question of temperament.
- Diet type
- Micropredator
- Staples
- Live and frozen daphnia, Bloodworm, Chopped earthworm, Live blackworm
Breeding
- Strategy
- Male builds a glued tunnel nest of plant material and fans the eggs
- Difficulty
- straightforward
- Parental care
- guarding
Requires a cold winter period first. Without one, most stock simply does not come into condition.
Tankmates and compatibility
Assessments are derived from stored traits by the compatibility engine, with the reasoning shown. A verdict is a statement about probability, not a guarantee — individual temperament can override it.
| Towards | Risk | What it means |
|---|---|---|
| Small fish | moderate | Anything that fits in the mouth is at risk once this species reaches adult size. |
| Adult dwarf shrimp | high | Cover reduces losses but rarely prevents them where the risk is high. |
| Shrimplets | near-certain | Determines whether a shrimp colony can grow rather than merely persist. |
| Snails | none | Applies to snails you wanted as well as snails you did not. |
| Long or trailing fins | none | Fin damage is an entry point for secondary infection. |
| Plants | 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.
- A short-lived annual-cycle fish kept at constant warmth burns through its life in about a year. The cold season is welfare, not authenticity.
- Collected from the wild in many places. Local collection is subject to fishing and wildlife law that varies by country and is frequently overlooked for a fish this common.
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
- Coastal and fresh waters across the northern hemisphere — Europe, northern Asia and North America
- Habitat
- Almost any cool shallow water: ditches, streams, ponds, estuaries and the sea itself, with populations that are entirely freshwater, entirely marine and everything between.
Legal status and responsible practice
Restriction note
Native across much of the northern hemisphere and introduced outside it. Where it is native, taking fish from the wild is usually governed by fisheries or wildlife legislation rather than by anything aquarium-specific — including, in several countries, a close season and a licence requirement that applies to a hand net as much as to a rod. Check the rules for your own country and water body before collecting; AquariumHQ has not checked them for any jurisdiction.
Where this species has been introduced, and what followed
Europe — recorded as introduced in 37 countries, first in Switzerland in 1870
EstablishedOther intentional release, from 1870. One of the most-studied fish in evolutionary biology, native across northern Europe, and recorded as an introduction in thirty-seven European countries.
- Deliberate stockingSomebody put the species into open water on purpose, for food, angling, ornament or mosquito control — frequently a government agency, and frequently before anyone considered the consequences.
What has been established
Nothing. The species is present outside its native range and no study has measured what it does there. The absence of data is not the absence of effect — it means the question has not been asked, and this is the ordinary state of the evidence for most aquarium species that have established somewhere warm.
EASIN — European Alien Species Information Network · EASIN catalogue record R06603 (apixg/catxg) · read 2026-08-30. A European network: the routes and effects recorded here are the ones documented in Europe. EASIN compiles national inventories, DAISIE and CABI rather than measuring, and its pathway assignments carry its own uncertainty flags, which are reported above where it sets them.
Never release aquarium life into the wild
Aquarium animals, plants, and aquarium water must never be released into ponds, rivers, canals, drains or the sea — not even in a country where the species is sold freely. Released fish and invertebrates establish populations that displace native species, and released plants and water carry pathogens, parasites and fragments capable of spreading without any animal at all. If you can no longer keep an animal, rehome it through an aquarium society, a retailer that accepts returns, or another keeper.
- Rehome through a local aquarium society, a specialist retailer or another keeper.
- Unwanted plants go in household waste or a hot compost heap, never in a watercourse or a garden pond.
- Never empty a bucket of tank water into a drain that discharges to open water.
- If an animal is beyond rehoming, ask an aquatic veterinarian about humane euthanasia rather than releasing it.
Legal status is recorded from the sources named and was correct on the verification date shown. Rules change, and sub-national rules often differ from national ones. Check the current position with the relevant authority before acquiring, selling or moving any animal or plant.
Evidence
Every stored value with the kind of support behind it and where to check it. Evidence type and confidence are separate axes: an editorial position held confidently and a measurement held tentatively are different things.
| Claim | Value | Evidence type | Confidence | Source |
|---|---|---|---|---|
| scientific name | Gasterosteus aculeatus | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Coastal and fresh waters across the northern hemisphere — Europe, northern Asia and North America | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 4–8 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 1–3 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 4–20 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 6.5–8.2 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 | ≥ 60 L | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum tank length | ≥ 80 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 5 | 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 2026-08-30. 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 checkableLimited evidence — treat with caution.
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. No checklist distribution statement is held for this species. The range on the page is editorial until one is.
What would improve this: Go and read a source. This is reachable and has not been reached.
adult sizeAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: size a well-kept specimen reaches — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
lifespanAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
temperatureAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
phAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
general hardnessAquariumHQ's own position, externally checkableAquariumHQ's own position, derived from evidenced inputs.
AquariumHQ's own position on a claim an external source could support.
What this kind of claim needs: what aquariumhq advises for keeping — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Go and read a source. This is reachable and has not been reached.
minimum tank volumeAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: minimum tank size — no external source is required, provided AquariumHQ shows its reasoning. No authority publishes this. AquariumHQ derives it, and the derivation is recorded with its inputs and assumptions.
What would improve this: Keep the rationale current. There is no source to find.
minimum tank lengthAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: minimum tank size — no external source is required, provided AquariumHQ shows its reasoning. No authority publishes this. AquariumHQ derives it, and the derivation is recorded with its inputs and assumptions.
What would improve this: Keep the rationale current. There is no source to find.
minimum group sizeAquariumHQ's judgement — no authority publishes thisAquariumHQ's own position, derived from evidenced inputs.
No external authority publishes this. The rationale carries the reasoning.
What this kind of claim needs: group size — no external source is required, provided AquariumHQ shows its reasoning. No external source is required for this class. AquariumHQ's position stands on its stated reasoning.
What would improve this: Keep the rationale current. There is no source to find.
Guides relevant to this species
Chosen from this record's own traits rather than listed on every page.
- Schooling and shoalingThis species is recorded as loose group, and the number it is kept in decides how it behaves.
- Predator and prey sizeIt takes adult dwarf shrimp, which decides what can share the tank.
- 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.
- How aquarium species get into the wildThis species has a documented introduction outside its native range, with the route recorded.
Group size and social behaviour
Shoals loosely outside the breeding season and stops entirely during it, when males become intensely territorial. A tank stocked for the shoal is wrong for three months of the year.