Harlequin Rasbora
Trigonostigma heteromorpha · family Cyprinidae
Also: Red Rasbora, Trigonostigma heteromorpha
Parameters
- Temperature
- 23–28 °C
- pH
- 6–7.5
- Hardness
- 4–12 °dGH
- Tank volume
- from 50 L
- Maximum size
- up to 4.5 cm
- Group size
- min 8, ideal 12
- Temperament
- Peaceful
- Swimming zone
- Middle
- Difficulty
- Beginner
- Lifespan
- 5–8 years
Description
The Harlequin Rasbora (Trigonostigma heteromorpha, 3.5–4.5 cm) is the #1 peaceful schooling tank mate for a male Betta. Unlike nippy barbs or hyperactive tetras, it never nips long flowing fins, swims calmly in the middle water column, and shares the exact same warm Southeast Asian biotope.
Care
Keep a school of 8–12+ in a 50 L+ planted aquarium (23–28 °C, pH 6.0–7.5, GH 4–12) with Cryptocorynes, Java ferns, floating plants, and gentle filtration flow.
Feeding
Easy omnivore: eats micro-pellets, crushed flakes, freeze-dried tubifex, and frozen daphnia or baby brine shrimp from the middle and upper layers.
Compatibility
- Betta
Betta splendens
Ideal peaceful tank mate for a male Betta in 50 L+ tanks: never nips fins and thrives at 25–27 °C.
Good
FAQ
- Why are Harlequin Rasboras the best tank mates for Betta fish?
- They are completely peaceful, never nip delicate Betta fins, occupy the middle water column away from the surface, and thrive in the same warm (25–27 °C), low-flow water.
Goldie editorial team
Practising aquarists with a combined 30+ years of experience · Biologists and editors, fact-checking against FishBase and Seriously Fish · Every piece is reviewed by a qualified ichthyologist before publication
Scientific board — ichthyologists and veterinarians
Ichthyologists and veterinarians with university degrees · Reference FishBase, Seriously Fish and peer-reviewed literature · Sign every reviewed article with their credentials shown
Sources
- FishBase: Trigonostigma heteromorpha · FishBase · 2026-05-22
- Seriously Fish: Trigonostigma heteromorpha · Seriously Fish · 2026-05-22