Rasbora - Harlequin (Trigonostigma heteromorpha)

The harlequin rasbora is a native of Malaysia, Singapore, Sumatra, and southern Thailand. It inhabits streams and waters that are characterized principally by low mineral content, high concentrations of dissolved humic acids, which is typical of water found flowing through peat swamp forests. The waterlogged soils of these forests inhibit the complete decay of leaf litter and result in the formation of peat, which leaches humic acids. These conditions resemble those found on in the blackwater habitats of South America. 

Of the more than five dozen species of rasbora, the harlequin is arguably the most popular of them all. Often referred to as a red rasbora, the body is a reddish copper color which is accented by a striking black wedge covering the rear half of the body, like a characteristic black "pork chop" shaped patch. The distinguishing triangular patch begins near the dorsal fin and comes to a point near the base of the caudal fin. These species look a lot like Rasbora espei and R. hengeli.

The harlequin rasbora is a shoaling fish, it should be kept in schools of 8 to 10 individuals. Since the fish is rather peaceful, it makes a good community fish. Schools of larger numbers make for a beautiful display. 

Rasboras are a true freshwater fish and are never seen in brackish waters. They prefer the lowland waters of southeastern Asia, where the water is soft and acidic. Harlequins prefer an environment with areas of dense vegetation, an open area for swimming, a dark substrate, and subdued lighting.

Water temperature is not critical, however, the ideal range is 74 to 78 F (23 to 26 C). The pH of the water should be slightly acidic, in the range of 6.0 to 6.5. An aquarium intended to house harlequin rasboras should be planted with live plants, with some open areas for swimming provided between stands of plants such as Cryptocoryne species, these being among the plants that inhabit the harlequin rasbora's native waters.

Harlequins make excellent community fish and will not nip at or quarrel with any other species.

Rasboras are undemanding when it comes to diet; they will readily accept flake, dried, frozen and live foods. A varied diet will ensure that digestive problems or susceptibility to disease do not occur.