Harlequin Rasbora (Trigonostigma Heteromorpha)

Harlequin Rasbora (Trigonostigma heteromorpha) — The Classic Schooling Fish of the Planted Aquarium

The Harlequin Rasbora (Trigonostigma heteromorpha) is one of the most iconic and enduringly popular fish in the freshwater aquarium hobby. Instantly recognisable by its warm copper-orange body and bold black triangular patch, the Harlequin has earned its place as a staple of the planted community aquarium — and for good reason. Hardy, peaceful, and strikingly beautiful in a school, it is the perfect fish for both beginners and experienced aquascapers alike.

Bold, Classic, Timeless

A school of 10 or more Harlequin Rasboras moving through a planted aquarium is a sight that never gets old. Their warm, metallic sheen and the sharp contrast of the black triangle create a cohesive, dynamic display that complements virtually any aquascape style — from lush Dutch plantings to minimalist Iwagumi layouts. Active and confident swimmers, they bring life and movement to the midwater column throughout the day.

Care Profile

• Scientific Name: Trigonostigma heteromorpha
• Origin: Southeast Asia — Thailand, Malaysia, Singapore, Sumatra; slow-moving streams and peat swamps
• Size: Up to 4–5 cm
• Temperament: Peaceful; an ideal community fish, best kept in schools of 10 or more
• Diet: Omnivore — accepts quality flake, micro pellets, frozen or live daphnia, brine shrimp, and micro worms
• Water Temperature: 22–28°C
• pH: 5.0–7.5 (adaptable; colour is most vivid in soft, slightly acidic water)
• Tank Size: Suitable from 60L upward
• Note: One of the hardiest and most adaptable rasboras — an excellent choice for community tanks and first-time fishkeepers

Aquascape Compatibility

The Harlequin Rasbora is plant-safe and compatible with a wide range of tankmates — corydoras, tetras, dwarf gouramis, and dwarf shrimp all make excellent companions. It thrives in planted aquariums with open midwater swimming space, fine-leaved plants, and a dark substrate that enhances its warm copper colouration. A versatile, forgiving, and beautiful fish that suits virtually any freshwater setup.

Hardy, beautiful, and endlessly rewarding — the Harlequin Rasbora is the schooling fish that belongs in every planted aquarium.