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CrayfishfreshwaterUndemanding

Dwarf Mexican crayfish

A 4 cm crayfish, small enough not to threaten most fish and interesting enough to carry a tank on its own. The orange form in trade is a captive-bred colour strain; the wild species is endangered in its only lake.

Quick profile

Scientific name
Cambarellus patzcuarensis
Adult size
3.5–5 cm (1.4–2 in)
Lifespan
1.5–3 years
Temperature
18–25 °C (64–77 °F)
pH
7–8.5
Hardness
8–20 °dGH
Minimum tank
40 L (11 US gal)
Minimum length
45 cm
Swimming zone
Bottom
Social
Loose group
Diet
Omnivore
Overall confidence
moderate confidence

What keeping this species involves

Hardy in hard alkaline water with adequate calcium for moulting.

Vegetated shallow lake margins.

Identity and names

Common name
Dwarf Mexican crayfish
Scientific name
Cambarellus patzcuarensis
Family
Cambaridae
Order
Decapoda
Class
Malacostraca
Also sold as
CPO, orange dwarf crayfish

Adult size and growth

3.5–5 cm (1.4–2 in)

Typical lifespan in an aquarium: 1.5–3 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: depressed — flattened top to bottom with a moderate. Assigned from what is typical of Cambaridae, not examined for this species.

Water and tank requirements

Floor area and hiding places; each individual needs its own shelter, particularly around moulting.

Temperature (°C)

Dwarf Mexican crayfish
18–25

Scale: 0 to 36 °C.

pH (pH)

Dwarf Mexican crayfish
7–8.5

Scale: 4 to 9.5 pH.

Hardness (°dGH)

Dwarf Mexican crayfish
8–20

Scale: 0 to 30 °dGH.

The bands AquariumHQ publishes for the dwarf mexican crayfish, 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

Hard alkaline water — Lake Patzcuaro

Water draining limestone, gypsum or volcanic mineral — Central American rivers, karst springs, hard-water lakes.

These species are usually easy in hard tap water and difficult in the soft, acidic water the hobby treats as the default. The commonest failure is the keeper softening water that did not need softening.

Conductivity
300–900 µS/cm
Flow
moderate
Dissolved oxygen
moderate
Seasonality
moderate

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 — Lake Patzcuaro. Hard alkaline water generally runs 22–30°C, and the advised band of 18–25°C is consistent with it. This is AquariumHQ's reasoning from the habitat, not a measurement of the species.
pHFollows the habitat this animal comes from
Follows the water this animal is recorded from — Lake Patzcuaro. Hard alkaline water generally runs 7.4–8.5, and the advised band of 7–8.5 is consistent with it. This is AquariumHQ's reasoning from the habitat, not a measurement of the species.
General hardnessSet by a requirement of the animal
Hardness here is set by moulting rather than by habitat. A crayfish rebuilds its entire exoskeleton several times a year and draws the calcium for it from the water and from its own gastroliths; in soft water the moult is where the animal dies. The band is a provision for that, and it is deliberately firmer than some of these species' recorded habitat.
AquariumHQ advises
18–25
The habitatHard alkaline water
22–30

Scale: 16.2 to 31.8 °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
7–8.5
The habitatHard alkaline water
7.4–8.5

Scale: 6.8 to 8.7 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.
RequirementValueNotes
Temperature18–25 °C (64–77 °F)Stability matters more than hitting an exact figure.
pH7–8.5A stable pH outside the ideal band is usually better than an unstable one inside it.
General hardness8–20 °dGHCheck your supplier's published figure before choosing species.
Carbonate hardness4–15 °dKHBuffering capacity — what stops the pH moving.
Minimum volume40 L (11 US gal)A floor, not a recommendation.
Minimum footprint45 cm longFloor area and hiding places; each individual needs its own shelter, particularly around moulting.
Water flowlowMatch the outflow to this rather than to the filter's rating.
Lid requiredRecommendedReduces evaporation and prevents accidents.
StructureMany small caves and dense cover. A moulting crayfish is defenceless and must be able to hide.

Group size and social behaviour

Tolerant for a crayfish, but individuals need separate shelters or they fight over them.

Structure
Loose group

Behaviour

  • Moults regularly and is vulnerable for a day or two afterwards.
  • Will catch a sleeping fish occasionally; slow bottom-dwellers are most at risk.

Feeding

Leave the discarded shell in the tank — the animal eats it to recover calcium.

Diet type
Omnivore
Staples
Sinking pellets, Blanched vegetables, Frozen foods, Leaf litter, Its own moulted shell

Breeding

Strategy
Female carries eggs and juveniles under the tail
Difficulty
straightforward
Parental care
carries eggs

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
TowardsRiskWhat it means
Small fishlowAnything that fits in the mouth is at risk once this species reaches adult size.
Adult dwarf shrimpmoderateCover reduces losses but rarely prevents them where the risk is high.
ShrimpletshighDetermines whether a shrimp colony can grow rather than merely persist.
SnailsmoderateApplies to snails you wanted as well as snails you did not.
Long or trailing finsnoneFin damage is an entry point for secondary infection.
PlantsnibblesTough 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.

  • Never release a crayfish. Non-native crayfish are among the most damaging freshwater invaders in Europe and carry crayfish plague, and keeping several species is prohibited in the EU.
  • Copper-sensitive, like all crustaceans.

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
Lake Pátzcuaro, Michoacán, Mexico — endemic and endangered in the wild
Habitat
Vegetated shallow lake margins.

What the checklists say

4 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.

StatusPlacesWhat this means
Introduced1A 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 stated3The 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.

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.

ClaimValueEvidence typeConfidenceSource
scientific nameCambarellus patzcuarensisObserved / measuredhigh confidenceCatalogue of Life; GBIF — Global Biodiversity Information Facility
native rangeLake Pátzcuaro, Michoacán, Mexico — endemic and endangered in the wildObserved / measuredmoderate confidenceGBIF — Global Biodiversity Information Facility
adult size3.5–5 cmAquarium-literature consensusmoderate confidenceAquariumHQ husbandry synthesis
lifespan1.5–3 yearsAquarium-literature consensusmoderate confidenceAquariumHQ husbandry synthesis
temperature18–25 °CAquarium-literature consensusmoderate confidenceAquariumHQ husbandry synthesis
ph7–8.5 pHAquarium-literature consensusmoderate confidenceAquariumHQ husbandry synthesis
general hardness8–20 °dGHAquarium-literature consensusmoderate confidenceAquariumHQ husbandry synthesis
minimum tank volume≥ 40 LAquariumHQ editorial positionmoderate confidenceAquariumHQ husbandry synthesis
minimum tank length≥ 45 cmAquariumHQ editorial positionmoderate confidenceAquariumHQ husbandry synthesis
carbonate hardness4–15 °dKHAquarium-literature consensusmoderate confidenceAquariumHQ 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. 4 distribution statements held from GBIF checklists — introduced in 1 country. Establishment means is reproduced from the source, never inferred from occurrence.

What would improve this: Go and read a source. This is reachable and has not been reached.

adult 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.

carbonate 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.

Guides relevant to this species

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