Taxonomy & naming
Nomorhamphus liemi was described by Vogt in 1977 from material collected in the highlands of southern Sulawesi (Celebes), Indonesia. The species sits in the order Beloniformes — the needlefishes, flyingfishes and halfbeaks — and within it the family Zenarchopteridae, the internally fertilising halfbeaks. This family is distinct from the egg-laying marine and brackish halfbeaks of the family Hemiramphidae: the zenarchopterids are freshwater fishes of South and Southeast Asia, and several of their genera, Nomorhamphus among them, have evolved internal fertilisation and live birth independently of the New World livebearers.
The genus name Nomorhamphus is built from Greek roots — combined with rhamphos, meaning a bill or beak, a reference to the elongated lower jaw that defines the halfbeaks. The specific epithet liemi is a patronym honouring Liem Bian Beek (Dr. Dig Liem), described as a friend, aquarist and collector of the author in Indonesia. The Catalog of Fishes (Eschmeyer, CAS) governs the valid name, and treats Nomorhamphus liemi Vogt, 1977 as valid.
Nomorhamphus is a genus of several small Sulawesi halfbeaks, and the group has been revised as new highland forms have been described; N. liemi is among the best known to aquarists, sometimes circulating in the hobby under informal subspecies or colour-form labels. Because Sulawesi's highland drainages are fragmented, members of the genus tend to be narrow-range endemics, and careful locality data matters for keeping wild forms distinct.
Morphology
Nomorhamphus liemi is a slender, elongate, surface-oriented fish. Males reach roughly 3 in in standard length, while females are larger and more robust, growing to around 3.5 in in total length; common length is about 3 in. The body is built for life just below the surface film: a straight back, an upward-tilted mouth, and fins set well to the rear, giving the fish the poised, hovering posture typical of halfbeaks waiting to seize prey from above.
The namesake feature is the "half beak" — an elongated, fleshy lower jaw that projects well beyond the short upper jaw. In N. liemi the tip of this lower jaw is often hooked or fleshy and, in males, can be darkly pigmented, making it one of the more conspicuous parts of an otherwise streamlined fish. Colour is brighter in this species than in many of its relatives, with red, orange and black markings on the fins and jaw that intensify in well-conditioned males.
Sexual dimorphism is clear once the fish mature. Males are smaller but more intensely coloured and carry an andropodium — a modified anal fin functioning as the intromittent organ for internal fertilisation, the halfbeak analogue of the poeciliid gonopodium. Females are larger, deeper-bodied and plainer, and a gravid female shows a swollen abdomen as the brood develops internally.
Habitat
The species is endemic to southern Sulawesi, where it occurs in the highland streams of the Maros region and surrounding uplands. These are not the warm, oxygen-poor ditches and ponds that many Central American livebearers tolerate; they are clear, flowing, well-oxygenated highland waters with a steady current, and this difference drives almost everything about how the fish should be kept.
FishBase records the species from freshwater, pelagic in habit, across a pH range of about 6.0 to 8.0 and a hardness of roughly 5 to 12 dH, in tropical conditions reported at around 68–75 °F — distinctly cooler than the tropical lowland norm. The fish lives at and near the surface, where the upturned mouth and projecting lower jaw are ideally placed to take insects falling onto the water. Its preference for cooler, current-fed, high-oxygen water makes it sensitive to the warm, sluggish conditions that suit lowland livebearers.
Because Sulawesi's freshwater habitats are localised and increasingly disturbed, the natural range of N. liemi is restricted, and the integrity of these highland streams — water quality, flow and surrounding land use — is the central conservation question for the species.
Feeding
Nomorhamphus liemi is more carnivorous than the typical livebearer. In the wild it feeds mainly on flying and surface insects, taken from the water's surface, and its reported trophic level of about 3.2 reflects this predatory, insectivorous diet. The whole body plan — the surface-hugging posture and the elongated lower jaw — is an adaptation for snatching prey that lands on or drifts at the surface, supplemented by some zooplankton and incidental items such as pollen.
In the aquarium this specialisation has to be respected. The fish does best on small, frequent meals of insect-based and live foods rather than a diet of dry flake alone: wingless fruit flies are an excellent staple, alongside other small live and frozen invertebrates. Several small feedings spread through the day suit its constant surface-grazing habit better than one or two large meals.
A varied, insect-rich diet keeps the fish in condition and supports breeding; an inadequate or overly plant-based diet leaves these surface predators thin and out of colour. Because they feed at the top of the water column, floating foods and items that stay near the surface are taken far more readily than anything that sinks quickly.
Mating
Like the New World livebearers, Nomorhamphus liemi reproduces by internal fertilisation, but the male's organ is the andropodium — a modified anal fin derived independently of the poeciliid gonopodium. The male uses this structure to transfer sperm to the female, so fertilisation occurs inside her body and the eggs develop internally rather than being scattered and fertilised in open water. This convergent live-bearing strategy is one of the most interesting things about the family Zenarchopteridae, which arrived at internal fertilisation entirely separately from the poeciliids.
Males are the smaller, more colourful sex and compete for females, their intensified fin and jaw coloration playing a role in display. Because the fish are surface-oriented and somewhat skittish, courtship and mating play out near the top of the water column, and a calm, well-covered tank helps pairs settle and breed.
The fish's nervousness has a direct bearing on reproduction: N. liemi is easily startled and prone to leaping, and a sudden shock can cause a pregnant female to miscarry her developing brood. Stable conditions, a secure cover, and minimal disturbance around gravid females are therefore part of getting them to carry broods to term.
Breeding
After internal fertilisation, the female carries the developing young and gives birth to free-swimming fry — Nomorhamphus liemi is a true livebearer, not an egg-layer (unlike some other halfbeaks, such as Hemirhamphodon, which lay eggs). Broods are small by livebearer standards, typically around nine to eleven young, but the fry are correspondingly large, fully formed and well developed at birth, already carrying the beginnings of the characteristic lower jaw.
Breeding is harder than the fish's livebearer status might suggest. The adults will cannibalise their own fry, so a dense thicket of floating plants — hornwort (Ceratophyllum demersum) is often recommended — gives the newborns cover, and many breeders remove the fry to a separate rearing tank to raise good numbers. Cool, very clean, well-oxygenated water suits both the parents and the developing young.
The susceptibility of gravid females to shock-induced miscarriage makes a quiet, stable, tightly covered aquarium essential through gestation. Given the right conditions — steady cooler temperatures, excellent water quality, plenty of surface cover and a steady supply of small live foods — the large, robust fry grow on well, but the species rewards patience and good husbandry rather than the casual, prolific breeding associated with guppies and platies.
In the aquarium
Nomorhamphus liemi is a rewarding but moderately demanding aquarium fish that should not be treated like an undemanding guppy. Its defining needs follow directly from its highland-stream origin: cooler water than most tropicals — roughly 72–75 °F is widely recommended, and it dislikes high temperatures — together with excellent water quality and good oxygenation supplied by efficient filtration and gentle flow. Around neutral pH suits it; it is not especially demanding about hardness, and has been kept and bred in moderately soft to medium-hard water.
The most important practical point is that these fish are skittish surface-dwellers that leap when alarmed, so a tight-fitting cover is essential — both to keep the fish in the tank and to protect startled, gravid females from shock. A calm location, subdued movement around the aquarium, and floating plants to give a sense of cover all help settle them. Feeding should centre on small, frequent meals of insect and live foods rather than dry flake alone.
Given clean, cool, well-oxygenated water, a secure lid and an appropriate insect-based diet, N. liemi is a hardy and characterful fish whose predatory surface behaviour and bright jaw markings make it a standout. Its requirements place it a step beyond beginner livebearers, but they are straightforward to meet for an aquarist willing to keep the water cool, clean and moving.
Conservation
Nomorhamphus liemi is assessed as Near Threatened (NT) on the IUCN Red List, under criterion B1b(iii), with the assessment dated 16 January 2020. The Near Threatened category reflects a species that does not yet meet the thresholds for a threatened listing but is close to qualifying, here on the basis of a restricted distribution combined with a continuing decline in the quality of its habitat.
That habitat pressure is the heart of the concern. As a narrow-range endemic of southern Sulawesi's highland streams, the species depends on clear, flowing, well-oxygenated freshwater, and it is vulnerable to anything that degrades those streams — changes in water quality, flow, land use and surrounding development across a naturally limited range. The criterion B1b(iii) listing specifically points to a decline in the extent or quality of habitat as the driver behind the assessment.
For aquarists, the responsible course is to favour captive-bred stock where available and to keep wild-collected locality forms distinct and well documented, so that the hobby supports rather than erodes the genetic and locality diversity of a restricted Sulawesi endemic. The species is harmless to humans; the conservation issue is the fragility of its highland-stream home, not the fish itself.