Harlequin Rasbora

Species Profile: Harlequin Rasbora

• Scientific Name: Trigonostigma heteromorpha
• Common Name: Harlequin Rasbora
• Adult Size: 1.75 to 2 inches (4.5 to 5 cm)
• Life Expectancy: 5–8 years (with proper care)
• Habitat: Slow-moving streams and peat swamps in Southeast Asia (Thailand, Malaysia, Singapore, and Sumatra) with soft, acidic, tannin-rich water and dense vegetation

Tank Requirements

• Minimum Tank Size: 10 gallons (38 liters) for a small group; 20+ gallons recommended for a proper school
• Ideal Temperature: 22°C – 27°C (72°F – 81°F)
• pH Range: 6.0 – 7.5
• Water Hardness: 2 – 15 dGH
• Temperament: Peaceful, social, schooling fish. Best kept in groups of 6 or more. Excellent community fish.

Diet & Nutrition

• Diet: Omnivorous
• Preferred Foods: High-quality flake food, micro pellets, freeze-dried bloodworms, daphnia, brine shrimp, and live/frozen options
• Feeding Tips: Feed small portions 1–2 times daily. Ensure all fish get access to food in a community tank.

Breeding & Spawning

• Breeding Difficulty: Moderate
• Spawning Type: Egg-scatterer
• Breeding Conditions: Soft, acidic water (pH ~6.0), slightly dim lighting, temperature around 26°C (79°F), fine-leaved plants like Java moss
• Spawning Behavior: Courtship involves males displaying to females; eggs are laid on the underside of leaves. Adults should be removed post-spawning to prevent them from eating the eggs. Eggs hatch in ~24 hours.

Appearance

• Coloration: Copper-orange to reddish body with a distinctive black triangular patch that starts near the dorsal fin and points downward toward the base of the tail
• Size & Shape: Streamlined, torpedo-shaped body perfect for schooling

Distinctive Features

• Iconic black "harlequin" triangle on the rear half of the body
• Active swimmers that stay in the mid to upper levels of the aquarium
• Ideal dither fish — helps shy species feel more comfortable
• Highly visible and vibrant in planted tanks with dark substrate and lighting contrast