Harlequin rasbora

Trigonostigma heteromorpha

FreshwaterFish

Care at a glance

Temperature: 72–82°F; 22–28°C
pH: 6.0–7.0
Adult size: 2 in; 5 cm
Minimum tank: 15 gal; 55 L

Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Beginner
Breeding: Medium
Rarity: Common
Family: Cyprinidae
Origin: Thailand, Sunda Islands

Overview

Keep them in a school of at least six, ideally more, in a tank of 55 liters or up. They are peaceful and spend most of their time in the middle of the water column, moving as a tight group. They eat just about anything small, like good flake, micro-pellets, and frozen or live bloodworms and daphnia. They make easy, calm community fish with other peaceful species that like the same soft, warm water.

In the wild

Harlequin rasboras come from slow, soft, acidic blackwater streams in Thailand and the Sunda Islands, the kind shaded by trees and full of leaf litter and roots. To match that, give them a dim tank with plenty of plants, some driftwood, and a soft sand substrate. Tannin-stained water from botanicals suits them well and brings out their color. Aim for a pH around 6 to 7 and temps in the mid 20s C.

Good to know

This is a small cyprinid (family Cyprinidae) that tops out around 5 cm. The big black triangle on the rear half of the body is its trademark. They are egg-layers that spawn by sticking eggs to the undersides of broad leaves, which is unusual for a rasbora. The species is listed as Least Concern with stable wild populations.

Did you know

They are one of the harder small egg-layers to breed at home because they need very soft, acidic water and will only spawn on the underside of a leaf, where the female flips belly-up to lay.

Weekly picks

Tank mates

Harlequin rasbora is a peaceful, schooling species that keeps to the middle. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Check the full mix in the stocking calculator