Taxonomy & naming
The Dutch zoologist Max Weber described Pseudomugil novaeguineae in 1907 from material collected in New Guinea. Eschmeyer's Catalog of Fishes records the valid name as Pseudomugil novaeguineae Weber, 1907; it was described in Pseudomugil and remains there, so no parenthetical authority applies. The family is Pseudomugilidae, the blue-eyes, within the order Atheriniformes — the silversides and their relatives. Blue-eyes sit close to the true rainbowfishes (Melanotaeniidae), sharing the same broad Australasian freshwater radiation.
Pseudomugil pairs the Greek pseudes, 'false', with the Latin mugil, 'grey mullet' — a nod to the superficial resemblance to mullets in body form. The epithet novaeguineae means 'of New Guinea', the island to which the species is endemic. Within the genus this is one of the broader-ranging, less specialised species. The blue-eyes as a group run small, carry the bright iris that names them, and the males flare paired, often filamentous fins when they display.
The genus has drawn steady taxonomic work as new species turn up in the rivers of New Guinea and northern Australia, and several of the better-known aquarium blue-eyes are close relatives. P. novaeguineae is set apart more by its distribution and meristics than by any one dramatic colour character — a reason not to take hobby material sold under the genus name as this species without checking.
Morphology
This is a small fish, reaching about 1.5 in standard length in Allen's field survey material. The body is fusiform — slender and torpedo-shaped — in the usual blue-eye mould, laterally compressed and built for the upper water column of flowing streams. Recorded fin counts are 3 to 5 dorsal spines with 6 to 9 dorsal soft rays, a single anal spine with 10 to 13 anal soft rays, in the divided dorsal arrangement shared across the family.
As in other blue-eyes, the brilliant iris is the feature that stands out, catching the light against an otherwise translucent to silvery body. In-life colour notes specific to P. novaeguineae are thin in the sources at hand. It is a more subdued fish than the intensely coloured congeners that fill the trade, and claims about its fin coloration or breeding dress are better taken from direct observation than borrowed from its showier relatives.
Sexual differences should follow the blue-eye pattern — males larger-finned and more strongly marked than females — but precise dimorphism data for this species was not in the cached references, so it is flagged as sparse rather than spelled out.
Habitat
The New Guinea blue-eye is endemic to central-southern New Guinea, ranging across the lowlands between the Fly River in the east and Etna Bay in the west, at roughly 3 to 7 degrees south. That is a broad band of flat, low-lying terrain. The width of its distribution across it is the central fact of its biology and the reason its conservation status is secure.
FishBase places the species in rainforest creeks and large streams of relatively flat lowland country. These are warm tropical waters — reported temperatures of about 26 to 30 degrees Celsius, pH from 6.5 to 8.0. That is a wide span, mildly acidic to mildly alkaline, and it fits a fish drawn from varied lowland catchments. The species is pelagic, living in open water of the upper column rather than down among the substrate.
A lowland rainforest setting points to clear or tannin-stained water, usually shaded, with submerged roots, leaf litter, and marginal plants for cover and feeding structure. As a pelagic micropredator of flowing creeks, P. novaeguineae would key on gentle current and surface insect activity — though fine-grained habitat notes for this species are limited in the sources.
Feeding
A trophic level estimated around 3.2 marks this out as a micropredator — small animal prey, not a herbivore or detritivore. Blue-eyes of the genus take small invertebrates and zooplankton: tiny crustaceans, insect larvae, and surface-fallen terrestrial insects caught in the upper water column they occupy.
In a rainforest creek, drifting and surface prey carried on the current would make up most of the diet, which suits the pelagic habit and small mouth. No species-specific feeding study for P. novaeguineae turned up in the cached sources, so this picture rests on its trophic level and on genus-level blue-eye ecology rather than gut-content work on the fish itself.
In the tank that means small, frequent feedings — micro-pellets, fine flake, and small live or frozen prey such as Daphnia, baby brine shrimp, and Cyclops. Because the genus feeds high in the column, foods that stay near the surface or sink slowly work best. Again, these notes are drawn from general blue-eye practice; no dedicated care source for this species surfaced in research.
Mating
Courtship observations specific to P. novaeguineae are thin in the sources consulted, so this section leans on the well-documented genus pattern rather than direct study of the fish. Blue-eyes are egg-scattering plant spawners with no parental care. Males display to females with paired fins erect, the bright iris and fin markings at their most vivid during courtship.
Across the genus, displaying males hold small territories among fine vegetation and court passing females by flaring their fins and deepening their colour, most active in the morning. A female is led into fine-leaved plants and releases a few adhesive eggs at a time — a handful each day over a long spawning period rather than one clutch.
Whether this species follows the pattern in every detail is not confirmed by the references, and no specific claim about its courtship colour or display is made here. What is safe to say: it belongs to a genus of continuous, plant-associated micro-spawners, and any breeding it shows should track that template.
Breeding
As with mating, breeding details for P. novaeguineae are limited in the sources, so what follows is general blue-eye biology rather than documented work on this fish. Blue-eyes lay small adhesive eggs that attach by fine filaments to fine-leaved plants or to synthetic spawning mops — the group's classic egg-scattering strategy.
Under good conditions spawning runs more or less continuously: a conditioned female drops a few eggs a day over many days, and breeders move the mops or eggs to a separate container, since the adults give no parental care and will eat both eggs and fry. The eggs are large for the size of the fish and hatch in anywhere from a few days to a couple of weeks depending on temperature. The tiny fry need very small first foods — infusoria, rotifers, or a commercial liquid fry food — before they take newly hatched brine shrimp.
No clutch sizes, incubation times, or rearing notes specific to this species were in the cached references, so none are quoted. Standard blue-eye methods should work, but anyone propagating it should treat the genus template as a starting point to confirm by observation, not as fact for this fish.
In the aquarium
This is a small, peaceful, schooling blue-eye for a well-planted tank kept as a group. Like the rest of the genus, it shows best in numbers — males display against one another, and the fish hold a loose shoal through the upper and middle column. A modest planted tank with fine-leaved plants, gentle flow, and subdued or planted-tank lighting matches where it comes from.
Keep water within the natural envelope: warm, roughly 26 to 30 degrees Celsius, pH from about 6.5 to 8.0. The wide pH tolerance makes it forgiving of varied tap-water profiles as long as conditions stay stable and clean, and soft to moderately hard water in that band is fine. As a small surface-and-midwater micropredator it wants small foods and is easily crowded out at feeding time, so tankmates should be similarly small and peaceful.
No dedicated care page for P. novaeguineae turned up in research — most hobby content under the genus name is really about showier congeners — so these notes come from the species' ecology and from general blue-eye husbandry. Treat them as a sound starting framework, not a species-specific protocol, and read the fish in front of you.
Conservation
The IUCN Red List rates Pseudomugil novaeguineae Least Concern (LC), in an assessment dated 4 June 2020. That status follows from its wide spread across the lowlands of central-southern New Guinea, between the Fly River and Etna Bay — a broad, well-watered range that gives it the resilience narrowly endemic relatives lack.
A multi-species rainbowfish assessment by the Australian government's environment department lists it Least Concern as well, in line with the IUCN. Unlike several of its lake-restricted relatives, this fish is not pinned to a single small basin where localised collecting, introduced predators, or habitat loss could take it out; its lowland range spreads that risk.
The lowland rainforests and waterways of New Guinea do face ongoing land-use pressure, and a Least Concern listing at the broad scale does not rule out local declines. The fish is harmless to humans and carries a low fishing vulnerability. As with all blue-eyes, aquarists can take pressure off wild populations by favouring captive-bred stock where it is available.