Taxonomy & naming
Pseudomugil luminatus was described in 2016 by Gerald R. Allen, Peter J. Unmack and Renny K. Hadiaty in the ANGFA journal Fishes of Sahul (volume 30, number 1, pages 950–961). It is a member of the blue-eye family Pseudomugilidae within the order Atheriniformes — a separate family from the true rainbowfishes (Melanotaeniidae), though the two groups are close relatives and share the silversides' general body plan. Eschmeyer's Catalog of Fishes records the valid name as Pseudomugil luminatus Allen, Unmack & Hadiaty, 2016; because the species was described in Pseudomugil, where it remains, no parenthetical authority is used.
The species was for some years circulated in the aquarium trade under informal labels before it received a formal name, and it is closely allied to Pseudomugil paskai of the Upper Fly River in Papua New Guinea. Allen and co-authors separated luminatus from paskai on a combination of fin-ray and scale counts and, above all, the bright neon-blue stripe along the uppermost body of luminatus. The two are similar enough that aquarium stock has at times been confused, and the 'red neon' fish long sold as a colour form of paskai is now referred to luminatus.
Morphology
This is a slender blue-eye reaching only about 0.5 in standard length in the type material — one of the smallest fishes commonly kept in the hobby. Aquarium sources sometimes quote up to roughly 1.5 in total length including the fins, but the scientific maximum is the sub-1 in SL figure. Like other Pseudomugil it has the family's two separate dorsal fins, large eyes, and an upturned mouth suited to feeding at and near the surface. Published meristics give a first dorsal of III–V spines and a second dorsal of 5–7 segmented rays (usually IV + 6), an anal fin of I,8–10 rays (usually 9), 8–10 pectoral rays, 25–27 lateral scales (usually 26), and 6 transverse scale rows.
The colour is the species' defining feature and the reason for its name. Live males are yellowish to intense reddish-orange over most of the body, overlaid by a neon-blue stripe along the uppermost back; the median fins carry scattered black spots, and the tips of the caudal lobes and the upper edge of the pectoral fin bear white-to-yellow markings. A mature male further develops an elongated filament from the second dorsal spine and the first segmented pelvic-fin ray, used in display. Females are far plainer, lacking the saturated red and the extended fin filaments.
Habitat
Pseudomugil luminatus is endemic to a very small area of southern Indonesian New Guinea, in the lowlands near Timika, the capital of Mimika Regency in Papua Province. FishBase records the distribution simply as southern New Guinea, Papua Province, Indonesia, and the IUCN assessment treats it as a single, narrowly restricted population — a feature that drives its conservation status.
Hobbyist accounts of the type area describe murky, slow-flowing swamp habitats with dense submerged vegetation, the kind of warm, soft-bottomed blackwater-influenced backwater typical of lowland New Guinea blue-eyes. Reported water is freshwater and tropical, slightly acidic to neutral, with the fish living among thick plant cover where it forms loose shoals near the surface. Because the documented range is essentially one small swamp system, this habitat description and the wild population are effectively one and the same — there is little margin of additional range to fall back on.
Feeding
In the wild the red neon blue-eye is a micro-predator and omnivore of the surface and upper water column, taking zooplankton, phytoplankton and small invertebrates. Its small, upturned mouth and large eyes are adapted to picking tiny prey from the surface film and the open water just below it, and its trophic level is estimated at around 3.1 — squarely that of a small invertebrate-feeder.
In the aquarium it needs correspondingly small foods. Live and frozen items such as Daphnia, Moina, newly hatched brine shrimp, microworm and similar micro-invertebrates are readily taken and bring out the best colour, supplemented with small floating dried foods sized for a fish with a tiny gape. Because individuals are so small and feed near the surface, frequent small feedings of finely sized food suit them far better than infrequent large meals, and dense planting gives them the slow, plankton-picking foraging style they show in the wild.
Mating
As in other blue-eyes, courtship is a male affair of colour and fin display rather than of nest-building or territory in any elaborate sense. Mature males flush their reddish-orange to neon colours to maximum intensity, raise and spread the filamentous second dorsal and the anal fin, and present to females among fine vegetation. Display is strongest where several males are present and competing, so the species colours up properly in a group rather than as an isolated pair.
Spawning is favoured by warmer water. A receptive female deposits eggs a few at a time onto plants or spawning mops over the course of several days rather than releasing a single clutch, and one male will mate with multiple females in succession. The fish is a continual, low-volume spawner under good conditions, the trickle of eggs spread across many days being characteristic of small Pseudomugil generally.
Breeding
Pseudomugil luminatus is an egg-depositing plant-spawner with no parental care, and like its relatives it will readily eat its own eggs and fry, so breeders separate eggs or spawning media from the adults. Females attach a small number of adhesive eggs daily, by fine filaments, to fine-leaved plants, moss or synthetic spawning mops; over a spawning period this adds up to a useful number of eggs even though no single day produces many.
Incubation is temperature-dependent and runs to roughly ten days at typical breeding temperatures, hatching sooner in warmer water. The fry are minute and require microscopic first foods — infusoria or paramecium-grade cultures — for around the first five days before they are large enough to take newly hatched brine shrimp and microworm. Patience and very small foods are the main demands; the species is otherwise willing to spawn given warmth, dense fine-leaved cover and conditioned adults. Reported lifespan is short, on the order of two years, which is typical for a fish this small.
In the aquarium
The red neon blue-eye is a peaceful nano shoaling fish best kept in groups of eight or more — more is better both for the fishes' security and for the male display that makes them worth keeping. For all its colour it is not a general community fish: it is too small and too gentle to compete with larger or boisterous tankmates, and is best housed in a species tank or alongside similarly tiny, peaceful companions such as other small blue-eyes and dwarf shrimp.
A densely planted aquarium with floating plants, driftwood and subdued, vegetation-filtered light suits it and encourages natural behaviour and colour. Hobby sources report a tolerance of pH around 6.5–7.5 and moderately hard water, with temperatures spanning roughly 63–79 °F, though the warmer end of that range better reflects its lowland tropical origin and promotes spawning. Stable, clean water and small, frequent feedings matter more than chasing exact numbers. Given its short lifespan and small size, it rewards a thoughtfully scaped nano setup far more than a busy community tank.
Conservation
Pseudomugil luminatus is assessed as Endangered (EN) on the IUCN Red List under criteria B1ab(iii), with the assessment dated 6 December 2019. The listing reflects an extremely restricted geographic range — essentially a single small swamp area near Timika — and continuing or projected decline in the extent and quality of that habitat. CITES and CMS have not evaluated the species, and its fishing vulnerability is rated low.
The central conservation concern is the same one that defines the species' biology: it is known from one tiny area, so any degradation of that habitat threatens the entire wild population at once, with no outlying populations to buffer a loss. The fish does breed readily in captivity and is now widely propagated in the hobby, so much of the trade is supplied by tank-bred stock rather than by wild collection. Sourcing captive-bred fish is the simplest way for aquarists to enjoy the species without adding pressure to a wild population that has very little room to spare.