Species profile
Harlequin Rasbora
Trigonostigma heteromorpha
Peaceful
Easy care
60 L minimum aquarium
3–5 cm adult size
Mid–top
Minimum group: 8
About this species
General notes for hobby use.
Classic peaceful shoaling rasbora. A planted, shaded aquarium with a proper group and open midwater swimming area suits it far better than a tiny starter tank.
Water parameters
Suggested general range for long-term care.
Temperature
22–26 °C
pH
5–7
GH
Up to 12 dGH
KH
Not yet documented
Flow preference
Low–moderate
Data confidence
Verified
Behaviour
General behaviour traits used by TanksConnected compatibility checks.
Minimum group size
Minimum group: 8
Tank zone
Mid–top
Territory level
None
Predation risk
Tiny fry
Bioload factor
0.5
Non-territorial and community-friendly. Keep at least eight, preferably more, with similarly peaceful fish and avoid large predators.
Compatibility flags
Quick cautions for common tank-planning issues.
Fin nipper
No
Plant safe
Yes
Shrimp safe
Yes
Snail safe
Yes
Cave breeder
No
Digs substrate
No
Jump risk
Yes
Natural history & care
Research-backed context for long-term aquarium care.
Lifespan
Not yet documented
Diet type
Omnivore
Minimum aquarium volume
60 L
Minimum footprint
60 × 30 cm
Accepted scientific name
Trigonostigma heteromorpha
Alternative names
Harlequin, Harlequin Fish
Native range
Malay Peninsula, southern Thailand, Singapore and Sumatra.
Natural habitat
Peat-swamp and forest-stream habitats with soft acidic water, leaf litter, roots and overhanging vegetation.
Diet & feeding
Feed small quality flakes/micro-pellets plus varied small frozen/live invertebrates.
Breeding & sexing
Research-backed guidance for identifying sexes and reproductive behaviour.
Sexing
Mature females are usually fuller and larger; males tend to be slimmer, with the dark wedge often appearing sharper or more extended.
Breeding
Unlike many cyprinids, females attach eggs to the underside of broad leaves. Adults provide no parental care and may eat eggs.