Taxonomy & naming
Parosphromenus anjunganensis was described by Maurice Kottelat in 1991. The type locality is Sungei Kepayang, a small blackwater stream approximately 4 mi south-east of the town of Anjungan in Kalimantan Barat (West Kalimantan), Indonesian Borneo, at approximately 0°20'N, 109°08'E. The species epithet anjunganensis is a toponym derived directly from that town name, following the standard Latin adjectival suffix for locality-based names.
Within the genus Parosphromenus — the licorice gouramis — the species is distinguished from its congeners primarily by the fin coloration of adult males: the dorsal, anal, and caudal fins are uniformly reddish-brown with a thin hyaline (clear) marginal band, a combination not replicated in other described species of the group. Meristic counts are 12–13 dorsal spines with 6–7 soft rays, and 11–14 anal spines with 9–11 soft rays. The Catalog of Fishes (Fricke, Eschmeyer & Fong) records the valid name as Parosphromenus anjunganensis Kottelat, 1991.
Parosphromenus is a genus of anabantoids in the family Osphronemidae, sister to Betta among the labyrinth fishes. All species are small, secretive, peat-swamp inhabitants of the Sunda Shelf region west of the Wallace Line, and all practice paternal cave-spawning rather than the open bubble-nesting typical of larger gouramis.
Morphology
Adult Parosphromenus anjunganensis are small even by licorice gourami standards, reaching approximately 1 in standard length (1–1.5 in in practice) with males typically the larger sex. The body plan is typical of the genus: slender, laterally compressed, with a somewhat pointed snout and large eyes set high on the head — an adaptation to the low-light conditions of blackwater peat-forest streams.
Sexual dimorphism is the most conspicuous feature of adult fish. Males in breeding condition display deep reddish-brown coloration across the dorsal, anal, and caudal fins, with each fin edged by a thin, glassy hyaline margin; this combination of saturated red-brown and contrasting clear border is the species' diagnostic character within Parosphromenus. The body ground colour in males tends toward darker barring on a brownish base, with nuptial coloration intensifying during courtship. Females lack the reddish fin pigmentation entirely and are generally plainer, with subdued barring and drab to translucent fins — a strong dichromatic difference that persists year-round, not only during spawning.
Habitat
This species is a stenotypic inhabitant of peat-swamp forest and blackwater streams in a small area of Kalimantan Barat, Borneo. The known range is confined to a handful of localities in the vicinity of Anjungan, making it one of the more geographically restricted members of an already narrowly distributed genus. The streams and swamps it occupies are shaded by intact peat-swamp forest canopy, and the water that drains through the deep peat layers acquires properties unlike almost any other aquatic habitat: extremely low pH (reported as low as 3.0, with an upper end around 6.5), negligible dissolved minerals producing very low conductivity and hardness (18–72 ppm), dark tea-coloured water stained by tannic and humic acids leached from the peat, and low dissolved oxygen relative to clear-water streams.
Water temperatures in these equatorial lowland systems are warm and relatively stable, typically 72–82 °F, varying more with ambient air temperature than with seasonal rainfall. Current is minimal to absent. The fish occupies leaf-litter beds, root tangles, and submerged woody debris at or near the substrate, rarely venturing into open water. As a labyrinth fish it can extract oxygen directly from air at the water surface, which is essential in the oxygen-depleted conditions of blackwater peat — surface access is not optional for this species.
Feeding
Parosphromenus anjunganensis is a micropredator, taking tiny aquatic invertebrates in the wild. The prey spectrum in peat-swamp blackwater is dominated by small crustaceans, copepods, insect larvae, worms, and other invertebrates found in leaf litter and the water column. Given its small gape and body size, prey items must be correspondingly minute.
In the aquarium the species does well on live and frozen micro-foods: Artemia nauplii (newly hatched brine shrimp), Daphnia, mosquito larvae (white and black), microworm, and similar fare. Dry prepared foods are accepted by some individuals but should not form the sole diet; small live invertebrates are important for conditioning breeding fish. Overfeeding is a risk given the small, still water volumes often used to keep licorice gouramis — light, frequent feeding matched to the fish's intake is preferable.
Mating
Courtship in Parosphromenus anjunganensis follows the cave-spawning pattern shared by most members of the genus. Males establish territories centred on a potential spawning cave — a crevice among roots, a hollow piece of driftwood, a overhanging leaf, or an artificial cave provided by the keeper — and display to females approaching the territory. The male's display includes assuming a near-vertical, head-down posture with fins fully spread, maximally intensifying his reddish-brown fin coloration to advertise quality to the female.
A receptive female approaches the cave entrance and may be courted at the threshold for some time before the pair enters together. Spawning occurs within the cave in a series of tight embraces, each producing a small number of eggs. The male positions the eggs on the cave ceiling or roof surface, often supporting them briefly in a sparse bubble cluster before they adhere. Only small numbers of eggs are produced per clutch relative to open-water spawners of similar size, which is consistent with the higher individual investment typical of cave-spawning labyrinths.
Breeding
Following spawning the male assumes sole guardianship of the cave and eggs; females should be removed or given ample space to retreat, as males may harass them once spawning is complete. The eggs develop attached to the cave ceiling, sometimes loosely supported by a few bubbles, and the male fans and tends them until hatching. Incubation takes roughly 24–36 hours at typical temperatures.
The fry become free-swimming approximately 4–6 days after hatching and initially remain near the cave entrance before dispersing. First foods must be very small: infusoria or commercial liquid fry food are appropriate at this stage, with Artemia nauplii introduced once the fry are large enough to take them. The adults do not typically predate free-swimming fry heavily, but a well-planted, species-only tank reduces stress on all parties. Water quality during rearing must be maintained at the soft, acidic parameters the species requires — hard or alkaline water at any life stage is poorly tolerated. Growth is slow, as is typical for the genus, and juveniles require several months before showing adult coloration.
In the aquarium
Parosphromenus anjunganensis is a species for dedicated keepers willing to replicate blackwater conditions faithfully; it will not prosper in standard hard or alkaline tap water. The aquarium should be small to medium in volume (10–20 US gal is ample for a pair or small group), heavily planted or furnished with leaf litter, driftwood, and caves — both to provide spawning sites and to create the visual shelter these secretive fish require. Filtration should be gentle, producing minimal current, and a layer of dried leaves (Indian almond, oak, or beech) on the substrate helps acidify the water and provides the tannin chemistry the species thrives in.
Water parameters should target a pH of 4.0–6.5, negligible hardness (under 50 ppm TDS is ideal), and temperature 72–82 °F. Reverse osmosis or similarly demineralised water is strongly recommended for this species — attempting to keep it in untreated hard tap water is unlikely to succeed. Surface access must be unobstructed; the labyrinth organ requires the fish to gulp atmospheric air regularly. The species is best kept as a species-only setup or with similarly small, non-competitive tankmates that tolerate the same extreme water chemistry. The Parosphromenus Project, an international group dedicated to licorice gouramis, maintains husbandry guidance and facilitates captive breeding programmes that help preserve genetic diversity of wild-collected populations in hobbyist hands.
Conservation
Parosphromenus anjunganensis is assessed as Endangered (EN) on the IUCN Red List under criterion B2ab(iii), assessed in January 2019. The primary driver of its threatened status is habitat loss: the peat-swamp forests of Kalimantan Barat have been extensively converted to oil palm plantation and other agricultural land uses over recent decades, eliminating or degrading the blackwater swamp systems that this highly stenotypic species depends upon. The IUCN assessment reflects a severely restricted area of occupancy combined with continuing decline in habitat extent and quality.
The species is not a mainstream aquarium fish and its commercial collection pressure is considered minor relative to habitat conversion. However, it occurs at very few known localities, meaning that local events can have population-level consequences. Conservation interest in the genus has led to the formation of the Parosphromenus Project, which works to document wild populations, maintain captive assurance colonies, and advocate for peat-swamp forest preservation in the region. Hobbyists who keep and breed P. anjunganensis contribute meaningfully to these assurance populations, and sourcing fish from documented captive lines rather than wild-caught specimens is strongly encouraged.