Harlequin Rasbora
Harlequin Rasbora (Trigonostigma heteromorpha) is one of the most iconic schooling fish in the freshwater hobby. The shimmering copper-orange body offset by a bold, precisely defined black triangular wedge running from the dorsal fin to the base of the tail gives this fish a graphic elegance that holds up beautifully in any planted aquascape. Under good lighting, the body takes on a rose-gold iridescence that few other small fish can match.
Feeding & Care Tip: Hikari Micro Pellets make an excellent daily staple. Supplement 2–3× per week with Hikari Frozen or Freeze-Dried Tubifex Worms or Hikari Frozen or Freeze-Dried Baby Brine Shrimp. Feed small amounts 2–3 times daily.
Native to peat swamp forests and slow-moving blackwater streams across Malaysia, Singapore, and Thailand, the Harlequin Rasbora adapts well to a range of conditions but shows its best color in soft, slightly acidic water with a planted background and dark substrate.
This is a true schooling species — keep a minimum of six, ideally ten or more. As with most schooling fish, larger groups produce noticeably deeper, more saturated copper tones. They are completely peaceful and make ideal companions for dwarf cichlids, Corydoras, small tetras, and other nano fish.
In the aquascape, Harlequin Rasboras are most effective as a mid-water schooling element against a planted background — the copper and black coloration reads clearly at any distance and contrasts beautifully with green or red plants.
Care & Ideal Parameters
| Difficulty | Easy |
| Temperament | Peaceful — Community |
| Typical Adult Size | 1.75 inches (4.5 cm) |
| Min. Group Size | 6 minimum — groups of 12+ produce noticeably brighter color |
| Ideal Temp | 72–82°F (22–28°C) |
| Ideal pH | 6.0–7.0 |
| Ideal GH | 2–8 dGH |
| Ideal KH | 1–6 dKH |
| Staple Food | Hikari Micro Pellets |
| Treat / Supplement | Hikari Frozen or Freeze-Dried Tubifex Worms, Hikari Frozen or Freeze-Dried Baby Brine Shrimp |
| Origin | Malaysia, Singapore, Thailand |
| Notes | Classic schooling fish. Soft slightly acidic water produces best copper-orange color. Completely peaceful. |
