Harlequin Rasbora

The harlequin rasbora (Trigonostigma heteromorpha, formerly Rasbora heteromorpha) is a peaceful, hardy, and popular freshwater aquarium fish. It is known for its coppery-pink body and distinctive black triangular patch.

Overview and Origin

• Common Name: Harlequin rasbora, harlequin fish
• Scientific Name: Trigonostigma heteromorpha (reclassified from Rasbora heteromorpha in 1999)
• Natural Habitat: Found in slow-moving forest streams and peat swamp blackwaters in Southeast Asia, including Malaysia, Singapore, southern Thailand, and Sumatra.
• Size: Grows up to 1.5 to 2 inches (3.5 to 5 cm).
• Lifespan: Typically 3 to 6 years.

Tank Requirements and Care

• Minimum Tank Size: A 20-gallon (approx. 75 liters) tank is recommended for maintaining a proper school.
• Water Parameters:
  • Temperature: 72°F–82°F (22°C–28°C)
  • pH: 5.0–7.0 (slightly acidic)
  • Best suited for soft, tannin-rich blackwater setups.
• Environment: Ideal for planted aquascapes with dim or filtered lighting and gentle water flow.
• Diet: Harlequin rasboras are omnivorous and readily accept:
  • High-quality flakes
  • Micro-pellets
  • Live or frozen foods like brine shrimp and daphnia

Behavior and Tank Mates

• Social Nature:
  Harlequin rasboras are highly social shoaling fish. They thrive in groups of at least 6 to 10 individuals to reduce stress and exhibit natural schooling behavior.

• Compatibility:
  These fish are exceptionally peaceful, making them perfect for community tanks with other small, non-aggressive species. Suitable tank mates include:

  • Small tetras
  • Peaceful barbs
  • Small catfish like Corydoras
  • Dwarf cichlids

  Avoid housing them with large or aggressive fish.

The harlequin rasbora is a delightful addition to any freshwater aquarium, offering vibrant colors, peaceful temperament, and a captivating schooling behavior that brings life to your tank.