
Trigonostigma heteromorpha
The harlequin rasbora is one of the most recognisable community fish: a copper-pink body with a dark triangular patch on the rear half. Native to peat swamps and slow streams in Southeast Asia, it tolerates a range of conditions but shows best colour in planted tanks with clean water and a group of at least six. Mid-water shoalers; peaceful with other small fish. Egg scatterers among fine plants; no parental care.
Flake or small granules; frozen daphnia or brine shrimp; micro foods for small mouths.
Frequency: 1–2× daily
Wedge marking intensifies when fish are settled and water quality is good.
Native Region: Southeast Asia (Thailand, Malaysia, Singapore, Sumatra, Borneo)
Blackwater and clear streams with leaf litter and plants.
Planted tank with swimming space; gentle flow; suitable for many community setups.
Activity Level: Moderate
Schooling Size: 6+ recommended
Tight school when comfortable; shy in bare or bright tanks.
Difficulty: Moderate
Type: Egg scatterer
Sexual Dimorphism: Females deeper-bodied; males slimmer and slightly more intense colour.
Inverted spawning under broad leaves; eggs adhesive; separate adults to reduce egg eating.
Substrate: Either
Plant Safe: Yes
Broad leaves (e.g. Cryptocoryne) for natural spawning behaviour.
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