三角灯 · Harlequin

Overview

A deep body, pinkish ground color, and broad dark triangular flank patch identify the familiar harlequin, Trigonostigma heteromorpha. It is a peaceful schooling fish widely produced in captivity. Blue, black, and golden domestic forms share the same basic care needs.

Distribution & habitat

Native records concern southern Thailand, Peninsular Malaysia, Singapore, and parts of Indonesia. Bintan is confirmed, while the extent on mainland Sumatra remains unclear and firm Bornean records are lacking. Body form varies somewhat between localities. Typical habitats are gently flowing, shaded forest streams with dense plants, soft slightly acidic to neutral water, and deposits of fallen leaves and branches.

Aquarium setup

A particular decorative style is unnecessary, but dark substrate, planting, and cover enhance the display. Soft sand, roots, branches, leaves, and floating plants create sheltered areas under subdued light. Microorganisms developing on leaf litter can supplement fry food. Select plants suited to the lighting.

Diet & feeding

Examination of wild fish reveals small insects, worms, crustaceans, and other zooplankton in the diet. Fine granules and flakes are easily accepted. Regular live or frozen Daphnia, Artemia, and bloodworms provide useful variety and support condition.

Behaviour & compatibility

Peaceful small companions with matching requirements are suitable, including some shy fishes. Eight to ten or more individuals encourage natural grouping, reduce nervousness, and stimulate male displays. Tankmate selection must still respect its small adult size.

Sexual dimorphism

Females are generally slightly larger and rounder through the abdomen. Males are slimmer and more colorful, and their dark flank patch often has a sharper outline than the more rounded female marking.

Breeding

Eggs adhere beneath broad leaves or to similar surfaces, with no parental care. A mature planted aquarium may produce a few fry. For controlled breeding, provide a dim separate tank, broad leaves or substitutes, and mesh underneath to protect detached eggs. Soft acidic water, temperatures near the upper end of its normal range, and gentle sponge filtration suit the arrangement.

Condition adults for several weeks with frequent small live and frozen meals. A cooler change of roughly forty to fifty percent can precede introduction of one or two pairs that evening. Morning courtship may involve repeated approaches before the pair turns upside down under a leaf to spawn in batches. Replace pairs if nothing happens within three or four days. Separate eggs and adults promptly afterward. Hatching normally takes one to two days, with free swimming around a week. Start with microscopic foods such as Paramecium before introducing microworms and Artemia nauplii.

Notes

Some mass-produced fish have weak coloration or body defects, making condition worth checking. Divergent genetic lineages in trade samples may represent unresolved lookalike taxa. Reports favoring older breeding fish concern relatives and do not define a mandatory age for this species.