Harlequin Rasbora

The Harlequin Rasbora (Trigonostigma heteromorpha) is a freshwater schooling fish valued for its copper body and bold black triangular patch that creates a clean geometric contrast in planted layouts. Native to Southeast Asia (Malaysia, Singapore, Sumatra), this species is popular in planted community aquariums because it combines visual impact with manageable care requirements. It is one of the most reliable schooling fish for nature-style aquascapes and mixed community tanks.

Appearance and Coloration

Harlequin Rasbora is known for clean pattern definition and color response that improves under stable water quality, varied feeding, and proper group size. In mature planted aquariums, the body pattern reads clearly even during fast schooling movement.

Size and Lifespan

• Adult size: 5 cm (2.0 inches)
• Typical lifespan: 4-6 years with stable parameters and quality diet

Ideal Aquarium Setup

This species performs best in a biologically mature aquarium that prioritizes oxygenation and stable chemistry.

• Tank size: 20 gallons (75 L)
• Temperature: 22-28 C (72-82 F)
• pH: 6.0-7.5
• Aquascape direction: dense planting, open midwater lanes, and darker substrate

Behavior and Temperament

Harlequin Rasbora is a peaceful and reliable schooling fish that settles quickly in community layouts. Keep groups of at least 8-10+ individuals so hierarchy and movement are distributed naturally. Good companion options include small tetras, rasboras, corydoras, and peaceful dwarf gouramis.

Diet and Feeding

Harlequin Rasbora is classified here as Omnivore. Build a varied schedule with high-quality staple foods, plus frozen or live options several times per week. A rotating diet supports immunity, activity, and stronger display color.

Breeding Notes

Most cyprinids in this group are egg scatterers. Conditioning with diverse foods and offering fine-leaved plants or spawning media can improve egg survival. If breeding is the goal, move adults after spawning to reduce egg predation.

Why Keep Harlequin Rasbora in a Planted Aquarium?

Harlequin Rasbora provides movement, contrast, and schooling structure that helps a layout feel alive without overpowering the design. For aquascaping-focused community tanks, it is a practical and visually rewarding choice.