Taxonomy & naming
Pseudomugil inconspicuus was described by the American ichthyologist Tyson R. Roberts in 1978. It belongs to the family Pseudomugilidae — the blue-eyes — within the order Atheriniformes, the silversides and their relatives. Eschmeyer's Catalog of Fishes records the valid name as Pseudomugil inconspicuus Roberts, 1978; the species was described in Pseudomugil and remains there, so no parenthetical authority is used.
The genus name Pseudomugil combines the Greek pseudes, false, with the Latin mugil, the grey mullet — a 'false mullet', after a superficial resemblance early naturalists drew to those fishes. The epithet inconspicuus is plain Latin for 'inconspicuous' or 'unremarkable'. It fits: FishBase reckons this small, dull fish is probably more widespread than the records suggest, missed because of its size and the muddy, hard-to-sample habitats it favours.
The blue-eyes are a modest radiation of small fishes across New Guinea and northern and eastern Australia. P. inconspicuus is among the more salt-tolerant of them, and over part of its range it lives alongside the closely related P. cyanodorsalis — sympatric, and a reminder that several lookalike small blue-eyes share these coastal waters.
Morphology
A very small fish, reaching about 1.5 in total length at most. The body is elongated in the usual blue-eye fashion — slender, laterally compressed, built for life among submerged roots and leaf litter rather than open water.
The meristics are spare and in keeping with that size: the dorsal fin carries 3 to 4 spines and 5 to 6 soft rays, the anal fin a single spine and 10 to 12 soft rays, with roughly 14 to 17 predorsal scales. As in other Pseudomugilidae the dorsal fin is split in two. Against the vivid reds and blues of its better-known congeners, this one is plain — true to its name.
Colour and live-pattern detail is thin. FishBase records no obvious sexual dimorphism in P. inconspicuus, which sets it apart from many blue-eyes, where males grow enlarged, filamentous fins and brighter colour. Beyond size and the basic fin and scale counts, the fine morphology stays poorly documented.
Habitat
A coastal, salt-tolerant blue-eye of mangrove country. P. inconspicuus turns up in mangrove swamps and saline creeks, along fringing coastal mangroves in brackish to fully marine water — a pelagic-neritic, non-migratory tropical species recorded between roughly 2 and 10 degrees south.
The known range sits in the south-west Pacific and probably runs from Toro Pass near the mouth of the Fly River in Papua New Guinea west to the Vogelkop (Bird's Head) Peninsula of Indonesian West Papua, and south to Woods Inlet in Darwin Harbour, northern Australia. The fish gathers among submerged mangrove roots and inundated leaves and branches, taking cover in the flooded forest floor. It can occur in large schools, and often in muddy, turbid water.
FishBase's modelled preferred temperature runs warm — about 28 to 29 degrees Celsius, fitting the tropical, near-equatorial range. Though essentially a brackish-and-marine fish, it is reported to adapt well to fresh water, in line with the broad salinity tolerance of several coastal blue-eyes. It is probably more widespread than the patchy record implies, overlooked for its size and the difficulty of sampling tangled, muddy habitat.
Feeding
A planktivore. In the mangroves and saline creeks it feeds on small drifting and suspended organisms — zooplankton and other tiny invertebrates carried among the roots and over the mud — taken in the water column rather than grazed off surfaces. FishBase places it at a trophic level of about 3.4, the mark of a small carnivore living mainly on invertebrate plankton.
The small mouth and slender body suit minute prey, and the habit of schooling in turbid water fits a fish that filters opportunistically through plankton-rich, sheltered backwaters. No gut-content or feeding study exists for the species, so the picture stays general — but the planktivorous habit is well established.
With the fish essentially absent from the hobby, there is little husbandry-based feeding data to draw on. By analogy with other small blue-eyes, captive specimens would likely want very small live and frozen foods. Specific care data for P. inconspicuus is genuinely sparse.
Mating
Reproductive behaviour specific to P. inconspicuus is poorly documented; the cached sources carry no detailed account of its courtship or spawning. What follows leans on the general biology of the genus, not on direct observation of this species — read it with that caveat.
Blue-eyes are egg-scattering plant-spawners. Males court females among fine vegetation or submerged roots, and in many species display with raised fins and heightened colour. P. inconspicuus is odd within the genus for showing no obvious sexual dimorphism, which hints that its courtship signalling may be plainer than that of the showier, strongly dimorphic blue-eyes — but that is an inference, not a recorded fact.
Between the muddy, hard-to-reach mangroves it lives in and its near-absence from the hobby, the mating system simply hasn't been studied. Rather than guess at spawning specifics, the honest line is that the data are sparse.
Breeding
Little firm, species-specific information on breeding survives for P. inconspicuus. The cached references hold no dedicated breeding account, and the fish is essentially unknown in aquaria, so the captive-breeding literature built up for popular blue-eyes like P. gertrudae or P. signifer doesn't reach it.
Blue-eyes in general are continuous, small-clutch spawners. They lay adhesive eggs on fine-leaved plants or root surfaces, the eggs hanging by fine filaments, the adults giving no parental care. P. inconspicuus probably follows this broad pattern, but the egg numbers, incubation period, and fry requirements particular to it are not on record.
The honest position — saying less over guessing — is that the breeding biology of P. inconspicuus is undescribed in the available sources. An aquarist attempting it would be working from analogy with related blue-eyes, not from any established protocol.
In the aquarium
In practical terms, this is not an aquarium fish. Hobby references describe the blue-eyes as small, colourful fishes from the freshwater streams and rivers of Australia and New Guinea, but none carries a care or breeding page for P. inconspicuus. Against congeners like P. gertrudae, P. luminatus and P. signifer, this brackish mangrove species is rare to absent in the hobby, and care data for it are sparse.
What little can be said comes from its wild ecology, not from tank experience. It is a warm-water fish — modelled preference around 28 to 29 degrees Celsius — and a coastal species that lives in brackish to marine conditions while adapting well to fresh water. Keeping it would point toward a warm, well-filtered tank, very small foods, and a group rather than a handful, since it schools in numbers; brackish conditions are a sensible starting point given where it comes from.
With no real husbandry to draw on, this section stays cautious. The plain colour that earned the name also means little of the visual appeal that drives demand for other blue-eyes — which is much of why it has never caught on in the trade.
Conservation
P. inconspicuus is assessed as Least Concern (LC) on the IUCN Red List, the assessment dated 3 June 2020. The listing reflects a species that, despite its patchy record, appears widespread across suitable coastal habitat and is not thought to face a high extinction risk.
FishBase reckons it is probably more widespread than the scattered collection records suggest — overlooked for its size and the inaccessibility of the muddy mangrove and saline-creek habitats it occupies. A distribution spanning southern New Guinea into northern Australia, paired with tolerance of brackish, marine and fresh water, gives it the ecological slack that supports the favourable status.
The fish is of no fisheries interest and is regarded as harmless. Like other mangrove-associated species, its main long-term vulnerability would be the degradation or loss of coastal mangrove rather than collection for the trade, in which it plays essentially no part. Under CITES and CMS the species is not evaluated.