Harlequin Rasbora Care Guide (Trigonostigma heteromorpha): Setup, Diet & Tank Mates
The Harlequin Rasbora (Trigonostigma heteromorpha) is one of the most popular community fish in the hobby, and for good reason. Its copper-orange body and bold black triangular patch stand out beautifully against green plants, and it is peaceful, hardy, and easy to keep. This guide walks through everything you need for a thriving school.
Quick care overview
- Adult size: about 1.5–2 inches (4–5 cm)
- Minimum tank size: 15–20 gallons for a school
- Temperature: 72–81°F
- pH: 6.0–7.5
- Temperament: peaceful, schooling
- Diet: omnivore
- Lifespan: 5–6 years
Tank setup
Harlequins are active mid-water swimmers that show their best color in a planted tank with some open swimming space. Darker substrate and a backdrop of plants make the orange and black really glow. They appreciate gentle to moderate flow and a secure, cycled tank. Live plants also give them cover and help keep water quality stable—browse live aquarium plants to set up their home.
Water parameters
This species is famously adaptable, tolerating a wide pH range, though it looks and breeds best in soft, slightly acidic water. What matters most is stability and clean water. Keep up with regular maintenance—our guide on how to do an aquarium water change covers the routine that keeps nitrates in check.
Diet and feeding
Harlequin rasboras are unfussy omnivores. Offer a quality flake or micro-pellet as a staple, and supplement with frozen or live foods such as daphnia, bloodworms, and brine shrimp for color and condition. Feed small portions once or twice daily.
Behavior and schooling
Keep harlequins in groups of at least 8–10. As a shoaling species they feel secure in numbers, stay out in the open, and display tighter, more natural schooling behavior. Small groups tend to be shy and less colorful.
Tank mates
Their peaceful temperament makes them excellent community residents. Great companions include other small rasboras and tetras, corydoras, otocinclus, dwarf gouramis, kuhli loaches, and peaceful dwarf shrimp. Avoid large or nippy fish. For broader schooling-fish tips, see our care basics for schooling fish.
Is the harlequin rasbora right for you?
Hardy, colorful, long-lived, and endlessly peaceful, the harlequin rasbora is one of the best beginner community fish available and a reliable choice for planted tanks. Find them among our freshwater fish.