Taxonomy & naming
Desmopuntius hexazona was described by Max Weber and L. F. de Beaufort in 1912, originally from the Mekong basin, and passed through several generic combinations in the decades that followed. It has been variously placed in Barbus and Puntius — the latter the sprawling wastebasket genus that held most Asian small barbs for much of the twentieth century — and is still commonly encountered in older aquarium literature as Puntius hexazona or Barbus hexazona.
The genus Desmopuntius was established by Kottelat (2013) in a sweeping revision that dismantled the old Puntius into multiple natural lineages. The Catalog of Fishes (Eschmeyer, CAS), the authority for valid names, places the valid combination as Desmopuntius hexazona (Weber & de Beaufort, 1912), with the parenthetical authority noting the move out of the original genus. Desmopuntius hexazona belongs to the 'hexazona complex' alongside D. pentazona and a handful of closely related banded species; the exact number of valid species in the group and their distributions have been subject to ongoing taxonomic revision, and specimens from different parts of Sundaland may yet represent distinct entities.
Morphology
Desmopuntius hexazona is a small, deep-bodied, laterally compressed barb reaching approximately 2 in in total length, with the compact, high-backed silhouette typical of the banded Desmopuntius. The ground colour is pale silvery-cream to pale gold, overlaid with six dark brown to black vertical bars that run from the dorsal surface down toward the belly. The bars are well-defined in healthy individuals, with the leading bar passing through or just behind the eye and the posterior bar crossing the caudal peduncle.
Fins tend to carry some orange to reddish tinting, particularly in well-conditioned fish, and the dorsal fin may show a dark margin. Sexual dimorphism is modest: females grow slightly larger and become noticeably rounder across the abdomen when gravid, while males are more slender and may show more intense fin colouration.
Habitat
The six-banded tiger barb inhabits peat swamps and blackwater forest streams across Sundaland — the Malay Peninsula (including Singapore), Sumatra and Borneo. These are among the most chemically distinctive freshwater habitats on earth: the water is deeply stained brown by humic and fulvic acids leaching from decaying plant matter, extremely soft, and often almost devoid of dissolved minerals. Seriously Fish records pH values as low as 3.0–4.0 in such peat-swamp waters, with negligible hardness.
FishBase characterises the species' typical habitat as undisturbed, shaded streams in swamp-forest with flowing acidic water, giving a reference pH around 5.5 and temperatures near 77 °F. Still-water bays, the margins of slow-moving blackwater streams and areas with dense submerged vegetation are typical microhabitats. The species is a benthopelagic schooler, moving through the mid- to lower water column among roots, leaf litter and aquatic plants. Water temperatures across this equatorial lowland range are warm year-round, broadly in the low-to-mid twenties Celsius.
Feeding
Desmopuntius hexazona is a micropredatory omnivore. Seriously Fish describes its natural diet as small insects, worms, crustaceans and zooplankton, supplemented with organic detritus and fine plant material. In the soft, blackwater peat-swamp environment, invertebrate drift — tiny aquatic insects and their larvae, copepods and ostracods — is a principal food source for small barbs of this kind.
In the aquarium it accepts dried foods including flakes and small pellets, but Seriously Fish notes that it should not be fed on dried foods exclusively: regular offerings of live and frozen invertebrates such as bloodworm, daphnia and brine shrimp are important for condition, colour and breeding readiness. A varied diet that approximates the protein richness of its wild prey keeps the fish robust and at its most colourful.
Mating
Like all barbs, Desmopuntius hexazona is an egg-scattering, non-guarding spawner. No pair bond is formed, no nest is built, and no territory is defended beyond transient courtship activity. When fish are in breeding condition — signalled by female abdominal fullness and heightened male colouration — a male will pursue a gravid female actively through vegetation or across the substrate, pressing close to her as eggs and milt are released simultaneously.
Spawning may involve multiple males competing for access to a single female in a group setting. The eggs are adhesive and settle among plant leaves, root tangles or into fine substrate. Neither parent shows any interest in the eggs once they are scattered, and adults in a breeding group will consume eggs given the opportunity.
Breeding
The six-banded tiger barb can be bred in aquaria, though its requirement for very soft, acidic water means it is more demanding than many popular barbs. Seriously Fish records it as an egg-scattering free spawner that breeds regularly when in good condition. A separate breeding tank with RO or very soft water adjusted to pH 5.5–6.5 and a temperature around 77–79 °F, fitted with fine-leaved plants or spawning mops and a mesh base to catch falling eggs, is the standard approach.
Well-conditioned fish introduced to such a setup will typically spawn in the morning, the female releasing adhesive eggs that fall among the plants or through the mesh. A single spawning may yield several dozen to a few hundred eggs. Adults eat eggs eagerly and should be removed promptly after spawning. Eggs hatch in roughly 24–36 hours at tropical temperatures, with larvae becoming free-swimming a few days later. First foods are infusoria and other microscopic prey, followed by freshly hatched brine shrimp nauplii as the fry grow. Growth is moderate.
In the aquarium
Desmopuntius hexazona is a specialist blackwater fish and is not well suited to the moderately hard, neutral water conditions that many community barbs tolerate without complaint. It thrives in soft, acidic water — pH in the range of 4.0–6.5 and very low hardness — that reproduces the peat-swamp chemistry of its home waters. Seriously Fish recommends keeping it in groups of eight to ten or more: as a schooling species it is more settled, more colourful and less prone to stress in a proper shoal.
Dark substrate, dim lighting, tannin staining from dried leaves or peat filtration, and dense planting with fine-leaved or floating species suit it well and encourage natural behaviour. Tankmates should share its water-chemistry requirements — other Sundaland blackwater species such as rasboras, small gouramis and chocolate gouramis are natural companions. Robust filtration with gentle flow is needed, but the fish is not demanding in terms of space given its small size. Fed well and housed correctly, it is a long-lived and rewarding aquarium fish.
Conservation
Desmopuntius hexazona is assessed as Least Concern (LC) on the IUCN Red List, with an assessment confirmed from 2019 sources. It is a broadly distributed species across several large Sundaland landmasses — the Malay Peninsula, Sumatra and Borneo — and its overall range remains intact enough to preclude threatened status at present.
Nevertheless, the peat-swamp and blackwater forest stream habitats on which this species depends are among the most threatened freshwater ecosystems in Southeast Asia. Deforestation for palm oil and timber, peat-swamp drainage for agriculture, and pollution of lowland rivers in Sumatra, Borneo and peninsular Malaysia have destroyed large areas of suitable habitat over recent decades. The loss of intact canopy over blackwater streams eliminates the shade, the allochthonous leaf-litter input, and the water chemistry that species like D. hexazona require. Singapore, where the species was historically present, has lost virtually all natural freshwater habitat. The species' dependence on undisturbed, shaded swamp-forest gives it a narrower effective range than its geographic extent might suggest, and continued monitoring of lowland stream habitats across Sundaland is warranted.