Taxonomy & naming
Betta antoni was formally described by Tan Heok Hui and Ng Heok Kiat Ng in 2006, based on specimens collected from the lower Kapuas basin in Kalimantan Barat (West Kalimantan), Indonesian Borneo. Eschmeyer's Catalog of Fishes records the valid name as Betta antoni Tan & Ng, 2006. The species is placed in the akarensis group, a cluster of mouthbrooding bettas distributed across Borneo and nearby parts of the Malay Peninsula that share general body form and reproductive strategy.
Within the akarensis group, B. antoni is distinguished from congeners by a distinctive dark bar running across the lower lip and chin, and by an unusually slim body — body depth falls in the range of 20.6–22.9% of standard length, shallower than typical for close relatives. Maximum standard length is recorded at 2 in SL from original specimens. These meristic and colour characters, taken together, allow reliable identification in the field and in the aquarium.
The specific epithet honours Irwan Anton, who assisted in the collection of specimens that formed the basis of the species description.
Morphology
Betta antoni is a slender fish reaching approximately 2 in standard length, making it a small member of the genus. The body is notably slim for the akarensis group, with depth at 20.6–22.9% SL — a diagnostic character separating it from the slightly more robust B. akarensis and allied forms. FishBase records a maximum of 2 in SL for the species.
The most reliable field mark is the black bar crossing the lower lip and chin, a character not present in the same form in other akarensis-group species. Ground coloration is typical of the group: a brownish or olive-tan body with iridescent lateral scaling, and fins that may carry blue-green iridescent highlights. As with other wild bettas, males show more intense coloration than females, particularly when displaying or stressed, and the fins are somewhat more developed in mature males. Females tend to be paler overall and rounder in the belly when gravid.
Habitat
Betta antoni is endemic to the lower Kapuas river basin in West Kalimantan, the western Indonesian province of Borneo. Within that system, it has been found in the upper reaches of clear, flowing forest hill streams — habitats characterised by leaf litter accumulation on the substrate, gravel and rock, and dense riparian forest providing heavy shade. These are not the still, tea-stained peat swamps associated with some Betta species but rather cleaner, lightly flowing waters with visible current.
Water conditions in the type-locality streams are soft and acidic, consistent with the Kapuas watershed's forested catchments: pH in the range of 5.7–6.3 has been recorded, with water temperatures reflecting the hill-stream environment at roughly 72–77 °F. As a labyrinth fish, B. antoni possesses the suprabranchial accessory breathing organ common to all bettas and gouramis, allowing it to take atmospheric air at the surface — an adaptation that confers some tolerance of the low dissolved-oxygen conditions typical of leaf-litter and still water, though in this species' natural streams that need is less pressing than in peat-swamp relatives.
The lower Kapuas basin is subject to extensive land-use change from logging, oil-palm expansion, and agriculture, making the persistence of the clear, forested stream habitat on which this species depends a continuing concern.
Feeding
Like all Betta species, B. antoni is a carnivore or insectivore in the wild, relying primarily on small invertebrates found at and below the water surface. In its forest hill-stream habitat this means aquatic insect larvae, terrestrial insects falling from the canopy, small crustaceans, worms, and similar prey items associated with the leaf-litter microhabitat.
In the aquarium the species accepts live and frozen foods readily — small daphnia, bloodworm, brine shrimp, and micro-invertebrates are all taken. Acclimatised individuals often accept high-quality dried foods including micro-pellets and freeze-dried preparations, though a diet with a significant live or frozen component is preferred for long-term health and breeding condition. Betta species generally do not graze plant material; the diet should be protein-rich and varied.
Mating
Betta antoni is a paternal mouthbrooder, the reproductive mode characteristic of the akarensis group and of mouthbrooding bettas generally. Courtship in mouthbrooding bettas follows a broadly consistent pattern: the male displays to the female through lateral posturing and finnage extension, intensifying colour and spreading gill covers to appear as large as possible. Receptive females respond by approaching and orienting alongside the male.
Spawning occurs through a series of nuptial embraces in which the male wraps his body around the female — the typical anabantoid embrace. Eggs are released in small batches during each clasp and are immediately fertilised. After each embrace, the pair collects the sinking eggs; it is the male who ultimately gathers and retains the clutch in his buccal cavity. Multiple embrace-and-collection cycles may occur over the course of a spawning event, with the male accumulating the full clutch before withdrawing to incubate.
Breeding
After spawning, the male B. antoni holds the fertilised eggs in his mouth and incubates them for approximately 12–17 days, eating nothing during this period. The eggs develop through the yolk-sac stage within his buccal cavity, and he releases fully formed, free-swimming fry once incubation is complete. The mouthbrooding male may periodically mouth and reposition the brood but does not expel and recollect it under normal conditions.
In the aquarium, conditioning pairs on live and frozen foods encourages spawning. A dedicated breeding tank with soft, slightly acidic water (pH around 5.5–6.5), warm temperatures in the low-to-mid 20s Celsius, and minimal filtration to avoid flow that stresses a holding male is recommended. The female should be removed after spawning to prevent the male being harassed. Fry released after the incubation period are relatively well developed and can typically accept newly hatched brine shrimp and micro-worms from the outset. Clutch size in mouthbrooding bettas is generally modest compared to egg-scattering species.
In the aquarium
Betta antoni is an uncommonly kept species in the hobby, available mainly through specialist wild-betta enthusiasts and breeders. Like other members of the akarensis group it is more active and less aggressive than the Siamese fighting fish, but males will still fight if housed together without adequate space and cover, and should generally be kept one male per tank or in a large, well-planted aquarium. A pair or a small group with one male and multiple females is the typical arrangement.
The species does best in a planted aquarium with soft, slightly acidic water reflecting its hill-stream origins — pH 5.5–7.0, temperatures in the low-to-mid 20s Celsius. Gentle filtration is important; strong flow is not natural to this fish and can stress a mouthbrooding male. Leaf litter on the substrate, driftwood, and dense planting create the shaded, structured environment that encourages natural behaviour and reduces stress. The species is sensitive to deteriorating water quality, and regular partial water changes are essential. Surface access must be unobstructed, as with all labyrinth fishes. Compatible tankmates, if any, should be small, peaceful, and non-fin-nipping; many keepers maintain wild bettas in species-only or betta-only setups to avoid competition and stress.
Conservation
Betta antoni is assessed as Endangered (EN) on the IUCN Red List. The designation reflects the species' narrow endemic range within the lower Kapuas basin — a system that, while one of Borneo's largest river networks, has experienced severe deforestation and land conversion across its catchment over recent decades. The clear, forested hill streams that the species occupies are among the habitats most directly affected by logging and oil-palm agriculture, which increase sedimentation, raise water temperatures, and alter the water chemistry of headwater streams.
As a species with a restricted and apparently fragmented distribution, B. antoni has limited resilience to habitat degradation; there are no known large alternative populations. Collection for the ornamental fish trade adds an additional pressure, though it is less intensive for this species than for the most popular wild bettas. The small number of dedicated hobbyists and specialist breeders working with B. antoni in captivity represents a modest but genuine conservation buffer. Maintaining a captive population and supporting habitat-protection efforts in the Kapuas basin are the most meaningful actions available to keepers of this species.