Harlequin Rasbora

The harlequin rasbora is easily recognized by the black, spearhead-shaped patch on the rear half of its copper-pink body. It is calm, compatible and hardy; swimming as a large school, it creates a warm mass of color in the aquarium.

It lives in the peat swamps and forest streams of Southeast Asia, in tannin-darkened, very soft and acidic water. Farm-bred fish are used to a wider range of values.

• Volume: at least 54–60 liters for a school of 8–10.
• Water: 23–26°C, pH 6–7, soft to moderately hard. A dark substrate and slightly tannin-stained water bring out its colors.
• Plants: broad-leaved plants such as Cryptocoryne and Anubias both reflect its natural habitat and are used for spawning.

Omnivorous. Small granules and flakes, frozen/live brine shrimp, daphnia and bloodworms. Its mouth is small; keep the food fine.

Peaceful and social. It should be kept in groups of at least 8, preferably more than 10; in larger numbers it is bolder and more colorful.

Good companions: neons and other small tetras, corydoras, kuhli loaches, otocinclus, dwarf gouramis, bettas, shrimp.

Avoid: large and aggressive fish, fin nippers.

The harlequin rasbora forms a tight school: at least 8, ideally 12 or more individuals. A large school wheels together through the middle layer of the aquarium, and the black triangle patterns look like a single unit. Kept in small numbers, the fish become shy and retreat among the plants.

The male-to-female ratio does not matter; in a mixed group the males occasionally court the females and their colors deepen.

Unlike other rasboras, it attaches its eggs to the underside of broad leaves: the pair turns upside down beneath the leaf to spawn. Breeding requires very soft (GH < 4), acidic water and broad-leaved plants. The eggs hatch in 24 hours; the parents may eat the eggs.

Hardy. Sudden water changes and poor water quality can lead to white spot and columnaris. A short quarantine is enough for store-bought fish.

In males the lower front corner of the black triangle is sharper and longer, extending towards the belly line; in females this corner is rounded. Females are plumper.