Taxonomy & naming
Trichopsis schalleri was described by Werner Ladiges in 1962. The specific epithet honours Dietrich Schaller, a German aquarist and tropical fish importer who collected or first introduced the species to European hobbyists; FishBase notes explicitly that the fish was named after him. The valid name as maintained in Eschmeyer's Catalog of Fishes is Trichopsis schalleri Ladiges, 1962, placed in the genus Trichopsis within the family Osphronemidae.
The genus Trichopsis — the croaking gouramis — comprises a small cluster of Southeast Asian labyrinth fishes historically difficult to distinguish by colour alone. Trichopsis schalleri is most readily separated from the more familiar T. vittata (croaking gourami) and the diminutive T. pumila (pygmy gourami) by meristic characters, fin-ray counts, and the striping pattern on the body. Molecular and morphological revisionary work on the genus has clarified species boundaries, though the three species remain superficially similar and are sometimes confused in the trade. The type locality falls within the lower Mekong drainage.
Morphology
Trichopsis schalleri is a slender, laterally compressed labyrinth fish reaching approximately 2 in standard length, putting it mid-sized within its genus — larger than T. pumila but comparable to T. vittata. The body is elongate relative to depth, giving the fish a more streamlined silhouette than the rounder gouramis of the subfamily Trichogastrinae.
The common name 'three-stripe gourami' refers to the lateral banding pattern: the body carries dark, roughly horizontal stripes or a series of spots and dashes along the flanks on a pale to brownish background, with iridescent blue and red pigment in the fins. Like all members of the family Osphronemidae, T. schalleri possesses a labyrinth organ — a complex, folded suprabranchial chamber that extracts oxygen directly from atmospheric air — whose presence allows the species to inhabit hypoxic water that would asphyxiate most teleosts. Males are generally more intensely coloured than females, with longer, more pointed dorsal and anal fin extensions, providing a basis for sexing conditioned adults.
Habitat
Trichopsis schalleri occurs across the lower Mekong basin, with records from Laos, Thailand, Cambodia, and Vietnam, and also from tributaries of the Chao Phraya watershed in central Thailand. Its habitat is characteristically lowland, still to slow-moving, and often seasonally inundated: swamp forest, peat swamps, floodplains, river backwaters, irrigation canals, paddy fields, and roadside drainage ditches all fall within its range.
Water chemistry in these environments is typically soft and acidic; Seriously Fish records a pH around 5 and temperatures from approximately 72 °F (72 °F), with hardness spanning a wide range (18–215 ppm) reflecting the diversity of habitats across the species' distribution. The shallow, often densely vegetated, and periodically stagnant nature of these waters drives dissolved oxygen low — conditions that the labyrinth organ allows T. schalleri to exploit without physiological stress. The fish tends to remain in the lower-to-mid water column and among marginal cover, rarely venturing into open water.
Feeding
Trichopsis schalleri is a micropredator and invertivore, subsisting in nature on small aquatic invertebrates and insect larvae. Like other members of the genus, it feeds at and just below the water surface as well as in the lower strata, taking any suitably sized prey items encountered among vegetation or in the water column.
In the aquarium it accepts a wide range of live and frozen foods — Daphnia, mosquito larvae, small bloodworm, Artemia — and will adapt to good-quality micro-pellets and fine flake. A varied diet including live or frozen invertebrates encourages breeding colour and condition, and because the species is small-mouthed, food particle size should be appropriate to its dimensions. Overfeeding in a small, low-filtration tank can degrade water quality rapidly, so modest, regular feeding is preferable to large infrequent meals.
Mating
Trichopsis schalleri is a bubble-nest builder, and the spawning behaviour is closely tied to the acoustic signalling that gives the genus its common name. Males in breeding condition produce audible croaking sounds — generated by vibrating specialised pectoral-fin tendons against the swimbladder — during territorial and courtship interactions. Rival males croak at one another in a form of acoustic tournament that helps establish dominance and access to females without necessarily requiring physical combat.
Courtship follows the pattern typical of the genus: the male builds a small bubble nest at the water surface, often anchored beneath a floating leaf or under marginal cover, binding the bubbles with mucus secreted from the mouth. When a female is receptive, the male courts her with fin displays and circling behaviour, eventually guiding her beneath the nest for spawning. The croaking intensifies during close-range interactions, and the quality and duration of the calls may signal male fitness to attending females.
Breeding
Spawning in Trichopsis schalleri is typical of bubble-nesting anabantoids. The pair embrace beneath the completed nest, the male wrapping around the female in a nuptial clasp during which eggs and sperm are released simultaneously. Fertilised eggs, which are slightly buoyant, float up into the bubble raft; the male retrieves any that sink and repairs the nest throughout the spawning period. Seriously Fish notes that a single pairing may yield 1 to 200 eggs per spawn, with successive spawns possible until the female is spent.
Following spawning, the male takes sole responsibility for guarding the nest and fanning the eggs. The female should be removed at this point to prevent aggression from the guarding male. At around 72–75 °F (72–75 °F), eggs hatch within roughly 24–48 hours, and the fry become free-swimming a few days later once the yolk sac is absorbed. The male continues to tend the fry briefly but should be removed once the fry are reliably free-swimming. First foods for the tiny fry are infusoria or commercial liquid fry food, graduating to newly hatched Artemia nauplii as they grow.
In the aquarium
The three-stripe gourami is well suited to small, heavily planted aquaria of 10 US gal or more. Its preference for still or barely moving water means that strong filtration turnover should be avoided; a sponge filter or low-output internal filter provides biological filtration without creating problematic currents. Surface access is essential — the labyrinth organ requires the fish to breathe atmospheric air regularly, and covering the tank with a close-fitting lid maintains warmth and humidity in the air space above the water, which matters for healthy labyrinth development especially in fry.
Water conditions should reflect the species' soft, acidic native habitat: pH in the range 5.5–7.0 and temperatures of 72–82 °F (72–82 °F) are appropriate. The species can be housed with other small, peaceable fish that share similar water-chemistry preferences — small rasboras, peaceful dwarf corydoras, and other micro-fish — but should not be mixed with boisterous or fin-nipping species. Males may quarrel with one another in confined spaces; a single male with one or two females is a practical grouping for a smaller tank. Dense planting with floating plants or leaves at the surface provides cover, breaks lines of sight between males, and supplies natural spawning sites.
Conservation
Trichopsis schalleri is assessed as Least Concern (LC) on the IUCN Red List, with the evaluation carried out in 2012 by Chavalit Vidthayanon. The species' wide distribution across the lower Mekong basin and central Thailand, combined with its tolerance of heavily modified habitats such as rice paddies and irrigation canals, underpins the favourable status: it is not considered at elevated risk of population decline at the range-wide scale.
Nonetheless, the landscapes the species inhabits are among the most intensively managed in the world. Pesticide application in paddy agriculture, wetland drainage, and water-quality degradation from agricultural runoff pose diffuse pressures on populations throughout the Mekong lowlands. The species' capacity to persist in marginal, human-altered habitats may mask localised declines where agricultural intensification is most severe. Collection for the ornamental trade is light relative to more popular anabantoids and does not appear to constitute a significant pressure at the range scale.