Taxonomy & naming
Oxyeleotris nullipora was formally described by Roberts in 1978 and belongs to the genus Oxyeleotris, a group of sleeper gobies with their centre of diversity in Australia and New Guinea. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the governing authority for the valid name and places the species in the family Eleotridae — the sleepers and gudgeons — rather than in the true gobies (Gobiidae, Gobionellidae, or Oxudercidae).
The distinction matters for anyone keeping or researching the fish. True gobies carry their pelvic fins fused into a cup-shaped adhesive sucker disc, a character unique to the Gobioidei. In sleepers and gudgeons the pelvic fins remain separate, and that single morphological difference is the clearest way to tell the two lineages apart. The hobby and trade frequently call eleotrids "gobies", and the name sticks, but Oxyeleotris nullipora is a gudgeon in the technical sense. Its wider genus relatives include some of the largest eleotrids in Australia and New Guinea, though O. nullipora itself is a small species. No earlier synonyms or combination changes are recorded in accessible sources for this species.
Morphology
Oxyeleotris nullipora is a small eleotrid; on the basis of the genus and the sparse data available for this species, total length is likely in the range of 1–3 in, though a confirmed maximum for this species specifically is not available in the accessible English literature and should be treated as provisional. The body form is elongate and somewhat cylindrical, as is typical for the genus — built for resting on or near the substrate and making short, directed dashes at prey rather than sustained open-water swimming.
Like other eleotrids, O. nullipora has two distinct dorsal fins, a broadly rounded caudal fin, and pelvic fins that remain separate from one another — the key character distinguishing the family from the fused-disc gobies. Coloration and sexual dimorphism in this species are not described in detail in available sources; in most small Oxyeleotris species the sexes are distinguishable by size and fin shape, with males often showing more extended rays, but specific data for O. nullipora are data sparse.
Habitat
Oxyeleotris nullipora inhabits freshwater streams and rivers in the Australasian region, broadly consistent with other small members of the genus from Queensland and New Guinea. The genus as a whole favours still or slow-moving fresh water with substrates of sand, gravel, or mud and the kind of cover — submerged wood, leaf litter, rock crevices — that suits a sit-and-wait predator.
Specific field data for O. nullipora are sparse, but Australasian freshwater drainages in the relevant range are typically warm to cool-temperate, with pH values in the range of 6.5–7.5 and temperatures broadly in the range of 68–77 °F. This is a strictly freshwater species; there is no indication that it uses brackish or estuarine habitats in the way that some other eleotrids (Dormitator, Eleotris, Bostrychus) routinely do.
Feeding
Oxyeleotris nullipora is a micro-predator, consistent with the feeding strategy of all eleotrids studied to date. Sleeper gobies in this genus are ambush hunters that remain motionless on the bottom and lunge at invertebrates and small fish passing within range. The diet in the wild would be expected to include small aquatic invertebrates, insect larvae, worms, tiny crustaceans, and opportunistically small fish — the same prey spectrum used by other small Oxyeleotris species.
In the aquarium, fish in this genus do best on varied small live and frozen foods: bloodworm, brine shrimp, daphnia, cyclops, grindal worms, and similar items. Like most eleotrids, O. nullipora would be expected to take dry flake poorly or not at all, and relying on flake alone risks nutritional decline and poor condition. Regular live or frozen offerings are the realistic baseline diet for any sleeper of this size.
Mating
The mating behaviour of Oxyeleotris nullipora has not been documented in the accessible literature, but the genus and family context is clear. Oxyeleotris is a group of resident, non-amphidromous eleotrids — the larvae do not develop at sea, and the whole reproductive cycle takes place in fresh water. This makes them fundamentally different from the amphidromous stream gobies (many Sicydiinae and Awaous, for instance) whose hatchlings are swept downstream to the ocean.
In closely related small Oxyeleotris and in the broader eleotrid pattern for resident species, males take up and defend a spawning site — a cave, crevice, undercut bank, or firm surface under wood or stone — and court ripe females there. Males in condition typically darken and become more territorial. Courtship leads the female to the spawning site, where eggs are deposited on a hard surface under the male's direct supervision.
Breeding
Consistent with the resident cave-spawner pattern for its genus, Oxyeleotris nullipora is expected to spawn by depositing adhesive eggs on a firm substrate inside a cave or crevice. The female lays the clutch and the male then takes over: he guards the eggs attentively, fans them with his pectoral fins to maintain oxygenation, and defends the site against intrusion until the eggs hatch. This is genuine paternal care rather than egg-scattering and abandonment.
Because the species is a resident freshwater spawner — not amphidromous — it is in principle captive-breedable in an aquarium, though it has not been documented as commonly bred in the hobby given its rarity in the trade. Providing appropriate caves or crevices, conditioning the pair on live and frozen foods, and maintaining good water quality and stable temperatures are the standard prerequisites. Specific hatch times and fry rearing data are not available for this species; fry of small eleotrids generally require micro-foods (infusoria or paramecia) before graduating to newly hatched brine shrimp.
In the aquarium
Oxyeleotris nullipora is not an established aquarium fish and is rarely if ever imported commercially; most keepers who encounter the genus do so through the more widely traded Oxyeleotris marmorata (the marble goby) or through chance collecting from Australasian waters. For anyone who does keep O. nullipora, the general care framework for small freshwater eleotrids applies: a well-filtered aquarium with clean, soft to moderately hard fresh water at roughly 68–77 °F and pH 6.5–7.5, a substrate of fine sand or gravel, and plentiful cover in the form of caves, hollow wood, and smooth stones.
Sleeper gobies rest on the bottom and make short dashes; they do not swim constantly and are not active open-water fish. They are territorial toward their own kind but can be kept with peaceful species that will not outcompete them for food. A lid is advisable, as most eleotrids will jump if startled. The main challenge in keeping the fish is diet — it needs small live and frozen foods and should not be expected to thrive on dry flake alone. Given its scarcity in the trade, obtaining this species typically means collecting it from its native range.
Conservation
Oxyeleotris nullipora has not been assessed on the IUCN Red List and is recorded here as Not Evaluated; we do not guess at a status where no assessment exists. The species is restricted to freshwater drainages in Queensland and New Guinea — a limited range that in principle makes it susceptible to local habitat degradation, but no specific population data are available to evaluate trends.
The pressures on Australian and New Guinean freshwater fishes broadly include habitat modification, altered flow regimes, introduced species, and land-use change in catchments, and small stream-dwelling eleotrids with restricted ranges are generally considered among the more vulnerable freshwater fish groups in the region. Because O. nullipora is essentially unknown in the aquarium trade, any trade pressure on wild populations is negligible. The absence of data is itself a conservation concern: very little is known about the species' abundance, population structure, or ecology, leaving it in a data-sparse category where precautionary attention is warranted.