Myers's hillstream loach
A flattened hillstream loach that holds onto rock in current using its fused fins as a suction surface. It is genuinely a specialist: the requirement is oxygen and flow rather than chemistry, and a hillstream loach in still water at the right pH is being kept badly in a way that takes months to become obvious.
Quick profile
- Scientific name
- Pseudogastromyzon myersi
- Adult size
- 4–6 cm (1.6–2.4 in)
- Lifespan
- 5–8 years
- Temperature
- 18–24 °C (64–75 °F)
- pH
- 6.5–7.8
- Hardness
- 4–15 °dGH
- Minimum tank
- 60 L (16 US gal)
- Minimum length
- 75 cm
- Swimming zone
- Bottom
- Social
- Loose group — at least 4
- Diet
- Algae grazer
- Overall confidence
- moderate confidence
What keeping this species involves
Needs cool, fast, saturated water and a mature biofilm to graze. Two of those three are the opposite of a standard community tank.
Fast, cool, highly oxygenated hill streams over smooth boulder and bedrock, clinging to rock in the current where algae grows on it.
Identity and names
- Common name
- Myers's hillstream loach
- Scientific name
- Pseudogastromyzon myersi
- Family
- Balitoridae
- Order
- Cypriniformes
- Class
- Actinopterygii
- Also sold as
- Pseudogastromyzon myersi, Pseudogastromyzon, Guangdong hillstream loach, Hong Kong hillstream loach
Adult size and growth
4–6 cm (1.6–2.4 in)
Typical lifespan in an aquarium: 5–8 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 grazing or sucking mouth. Assigned from what is typical of Balitoridae, not examined for this species.
Water and tank requirements
A rheophilic fish needs a length of current and a large area of hard grazing surface, both of which are footprint 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: Cool, fast, oxygen-saturated southern Chinese hill streams. What defines this habitat is turbulence and oxygen rather than dissolved mineral, and the chemistry band is wide because the local geology varies while the hydrology does not.
Where these figures come from
Habitat class
Hill stream and rapids
Fast, cool, oxygen-saturated running water over rock and gravel, typically at altitude or on a steep gradient.
Oxygen and flow are the requirement, not the chemistry. A hill-stream species in still water at the right pH is being kept badly, and the failure is slow enough that the keeper usually blames something else.
- Conductivity
- 50–300 µS/cm
- Flow
- high
- Dissolved oxygen
- near saturation
- 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.
- 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 | 18–24 °C (64–75 °F) | Stability matters more than hitting an exact figure. |
| pH | 6.5–7.8 | A stable pH outside the ideal band is usually better than an unstable one inside it. |
| General hardness | 4–15 °dGH | Check your supplier's published figure before choosing species. |
| Minimum volume | 60 L (16 US gal) | A floor, not a recommendation. |
| Minimum footprint | 75 cm long | A rheophilic fish needs a length of current and a large area of hard grazing surface, both of which are footprint rather than volume. |
| Water flow | high | Match the outflow to this rather than to the filter's rating. |
| Lid required | Recommended | Reduces evaporation and prevents accidents. |
| Structure | Smooth boulders and slate, strong laminar flow, high oxygen, and mature biofilm on hard surfaces. |
Behaviour
- Clings to smooth rock in the strongest flow in the tank and grazes in short darting movements.
- Spars with other males over grazing patches, briefly and without damage where there is room.
Telling males from females
Males are more strongly patterned with a broader head; females plainer and rounder. The difference is not obvious outside breeding condition.
Feeding
A grazer of the film that grows on rock in current. A newly set-up tank has none, and a loach put into one starves while the keeper watches it apparently feeding.
- Diet type
- Algae grazer
- Staples
- Biofilm and aufwuchs grazed from rock, Algae wafers, Blanched vegetables, Spirulina-based foods
Breeding
- Strategy
- Eggs deposited in gravel depressions; not commonly achieved in aquaria
- 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.
| 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 | low | 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 | grazes-algae | 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.
- Starves in new tanks. A hillstream loach should go into a mature tank with visible algae on hard surfaces, not into a clean one.
- Warm still water kills it slowly through oxygen rather than temperature, and the two are hard to separate at the point of diagnosis.
- Almost all stock is wild-caught from a small area of southern China.
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
- Southern China — Guangdong and Hong Kong, and adjacent Guangxi
- Habitat
- Fast, cool, highly oxygenated hill streams over smooth boulder and bedrock, clinging to rock in the current where algae grows on it.
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 | Pseudogastromyzon myersi | Observed / measured | high confidence | Catalogue of Life; GBIF — Global Biodiversity Information Facility |
| native range | Southern China — Guangdong and Hong Kong, and adjacent Guangxi | Observed / measured | moderate confidence | GBIF — Global Biodiversity Information Facility |
| adult size | 4–6 cm | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| lifespan | 5–8 years | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| temperature | 18–24 °C | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| ph | 6.5–7.8 pH | Aquarium-literature consensus | moderate confidence | AquariumHQ husbandry synthesis |
| general hardness | 4–15 °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 | ≥ 75 cm | AquariumHQ editorial position | moderate confidence | AquariumHQ husbandry synthesis |
| minimum group size | ≥ 4 | 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.
- Wild conditions and aquarium recommendationsThe water band on this page is an AquariumHQ position with a stated reason, not a measurement of a river.
Group size and social behaviour
Males hold small grazing patches on rock and spar over them without harm where there is enough surface. Too little rock turns display into attrition.