Fish - Trigonostigma heteromorpha - Harlequin Rasbora

The Harlequin rasbora (Trigonostigma heteromorpha) is a beautifully colored, peaceful aquarium fish originating from the tropical waters of Asia, particularly from the regions of Thailand, Malaysia, and Sumatra. The most characteristic feature of this species is the triangular, bluish-black spot on its side, which tapers toward the tail. The dorsal side is olive green, while the underside has a silvery hue. The caudal spot of mature males has a straighter front edge and a sharper rear tip, while females are rounder.

It is recommended that at least eight individuals of this species be kept to achieve natural schooling behavior. The Harlequin rasbora is entirely peaceful, making it compatible with any ornamental fish that does not threaten it. It is an ideal choice for Southeast Asian biotope aquariums, where it can be an excellent companion to danios, other rasboras, dwarf gouramis, bottom-dwelling loaches, and barbs.

In mixed community aquariums, it can often be seen cohabiting well with livebearers, calmer dwarf cichlids, catfish, minnows, and rainbowfish.

The appropriate aquarium size is a minimum of 65 liters, but up to 10 Harlequin rasbora can be kept in an 85-liter aquarium. It is beneficial to provide roots, dense vegetation, and open space for swimming in the decoration. The Harlequin rasbora prefers a combination of thick vegetation and open space. As for water parameters, the temperature should be maintained between 24-28 °C, the pH between 6-6.5, and the hardness between 4.5-8.5 NK°. The expected lifespan of the Trigonostigma heteromorpha is between 5 and 6 years.

Overall, the Harlequin rasbora is a peaceful, sociable, and visually striking aquarium fish that can be a perfect choice for those who want to keep a small-sized, yet colorful, fascinating species in their aquarium.