Taxonomy & naming
Trichopodus microlepis was described by Albert Günther in 1861. The valid name is recorded in Eschmeyer's Catalog of Fishes as Trichopodus microlepis (Günther, 1861); the parenthetical authority indicates the species was originally placed in a different genus and later transferred to Trichopodus. The genus Trichopodus contains several of the larger and more familiar gouramis, including the three-spot gourami (T. trichopterus) and the snakeskin gourami (T. pectoralis), all members of the family Osphronemidae.
The specific epithet microlepis is Latin for 'small scales', from Greek mikros (small) and lepis (scale) — referring to the notably fine, small scales that give the fish its smooth, almost polished appearance compared with many related species. The common name moonlight gourami alludes to the pale, silver sheen of the body, which can reflect light with a faint luminescence. On some trade lists the fish appears as moonbeam gourami, which carries the same meaning.
Morphology
The moonlight gourami is a large, laterally compressed labyrinth fish reaching around 5.5 in total length according to FishBase, with Seriously Fish citing up to 6 in standard length for the largest specimens. The body is deep and oval, tapering toward a slightly forked tail, and the overall silhouette is more elongate than the rounder three-spot gourami but not so slender as a snakeskin. The scales are notably small and numerous — hence the specific epithet — and give the fish a smooth, fine-grained surface texture.
Colouration is understated: the base colour is silver to pale greenish-silver, with a faint iridescent wash that shifts between green and blue depending on the light. There are no bold bars or spots. Sexual dimorphism is modest but reliable: males develop bright reddish-orange to reddish-brown pelvic fins as they mature and during the breeding season, while females' pelvic fins are pale yellow. Males also develop a more pointed dorsal fin tip with age. Like all Trichopodus, the pelvic fins are highly modified into long, filamentous feelers — thread-like sensory extensions that the fish uses to probe the environment — a hallmark of the gourami group.
Habitat
Trichopodus microlepis is native to the Mekong basin, with its natural range centred on Cambodia and Vietnam; the IUCN assessment also lists Lao PDR and Thailand as part of the native range, covering the Mekong and Chao Phraya basin drainages. The species has also been introduced to Singapore and, according to Seriously Fish, to Colombia, through the aquarium trade. FishBase records it as naturally absent from Thailand's mainstream trade centres, with Thai populations originating from introductions.
The fish inhabits lowland freshwater wetlands: ponds, bogs, swamps, floodplains, and slow-moving or still water bodies with dense aquatic and marginal vegetation. These are shallow, warm, often oxygen-depleted environments — exactly the conditions that favoured the evolution of the labyrinth organ in osphronemid fishes. Water chemistry in the natural range is slightly acidic to neutral: FishBase records pH 6.0–7.0 and temperature 79–86 °F; Seriously Fish gives pH 6.0–7.5 and 77–86 °F, with hardness ranging from very soft to moderately hard (dH 2–25). Dense vegetation is essential habitat structure, both for cover and as material and anchor-points for the bubble nest.
Feeding
In the wild, Trichopodus microlepis is an omnivore with a strong bias toward animal matter. FishBase records the natural diet as zooplankton, small crustaceans, and aquatic insects — the kind of invertebrate prey available in the vegetated still-water habitats the species favours. As a large-bodied gourami, it is capable of taking sizeable food items and is likely an opportunistic feeder on whatever invertebrates are accessible at different seasons.
In the aquarium it accepts a broad diet without difficulty: high-quality dried foods (flake, pellets, granules) form a practical staple, supplemented with frozen or live foods such as bloodworm, Daphnia, brine shrimp, and similar small invertebrates. Vegetable matter — blanched spinach, spirulina-based foods — rounds out the diet and supports long-term condition. Because this is a large fish, feeding portions should be appropriately sized, and overfeeding in a large gourami tank leads quickly to water quality problems.
Mating
The moonlight gourami is a bubble-nester. As breeding season approaches — or year-round under stable aquarium conditions — the male constructs a floating raft of bubbles at the water's surface, binding each bubble with mucus to produce a cohesive foam structure. The nest is typically anchored beneath floating plants or marginal vegetation, which provide both structural support and some surface cover. Males are territorial around the nest site and will display aggressively toward rival males, flaring fins and intensifying the red-orange pelvic fin colouration.
Courtship involves the male driving and circling the female, displaying with spread fins and approaching the surface to check and repair the nest. Receptive females follow the male toward the nest; unwilling females are pursued persistently and can suffer fin damage in a confined aquarium, making it advisable to provide ample space and sight-breaks or to condition the pair separately before introducing them. The characteristic embrace of labyrinth fish — where the male wraps his body around the female in a C-shape to fertilise the eggs — takes place at the surface beneath the nest.
Breeding
Spawning occurs at the surface beneath the bubble nest. Eggs are buoyant and float up into the nest after the pair's spawning embrace; FishBase records clutch sizes of 500–1,000 eggs per spawn, making this a prolific species. The male immediately takes charge of nest maintenance and egg care, collecting any sinking eggs in his mouth and replacing them in the foam. The female should be removed after spawning, as the male will defend the nest against her and may attack her.
SeriouslyFish notes that the moonlight gourami is not the easiest gourami to breed successfully, despite the male's attentive behaviour. Eggs and early fry are sensitive to water chemistry fluctuations; stable, soft to slightly hard, warm water in the range of 82–86 °F aids hatching. Eggs hatch in roughly 24 hours at higher temperatures; fry are initially very small and require infusoria or other tiny first foods before graduating to newly hatched brine shrimp and powdered fry food. The male should be removed once the fry are free-swimming. Growth is steady under good conditions, with juveniles developing the characteristic fine scaling and silver sheen within a few weeks.
In the aquarium
The moonlight gourami's combination of large size, peaceful temperament, and subtle beauty suits it to spacious community aquaria. Because adults reach 5.5–6 in, a tank of at least 47 in is appropriate for a pair or small group; taller tanks with plenty of open swimming space in the middle and upper strata work well. Floating plants or broad-leaved surface cover are appreciated, providing resting spots and a surface layer that supports the bubble-nesting instinct — and that keeps surface turbulence low enough that the fish can breathe comfortably at the surface.
Water conditions should reflect the species' natural range: warm (79–86 °F), slightly acidic to neutral (pH 6.0–7.5), and soft to moderately hard. Filtration should be efficient but gentle — strong currents stress labyrinth fish and disrupt bubble nests. Males can be territorial toward each other and toward other large, similarly shaped fish; keeping a single male with one or more females generally produces a more peaceful dynamic than multiple males together. Compatible tankmates include medium to large peaceful fish that occupy different areas of the water column: large rasboras, peaceful barbs, angelfish, and similarly sized catfish. The fish is long-lived in good conditions and is also used as a food fish in its native countries, where it has minor commercial significance alongside its substantial role in the ornamental trade.
Conservation
Trichopodus microlepis is assessed as Least Concern (LC) on the IUCN Red List, with the evaluation published in 2012 based on an assessment carried out on 4 March 2011 by Chavalit Vidthayanon. The population trend was recorded as stable at the time of assessment. The species is locally common in suitable wetland habitats across the Mekong basin, and its range spans multiple countries — Cambodia, Lao PDR, Thailand, and Vietnam — providing some buffer against localised declines.
The IUCN assessment notes threats from residential and commercial development and from pollution affecting freshwater wetland habitats in the region. Ponds, bogs, and swamps throughout the Mekong lowlands face ongoing drainage, conversion for agriculture, and degradation from agricultural runoff and industrial pollution. These pressures are general across lowland Southeast Asian wetland fish rather than specific to this species. The moonlight gourami is also significant as a food fish in its native countries, where it is harvested from wild wetlands as well as raised in aquaculture. Active conservation measures were not in place at the time of assessment, the species' broad range and stable numbers being judged sufficient at that time.