Taxonomy & naming
Aurich described the species in 1935 in a different genus, and it is now placed in Oryzias; the authority is therefore in parentheses. It is one of several ricefishes endemic to the Malili lake system, which holds Lakes Matano, Mahalona and Towuti, and its relatives in the system include O. marmoratus and O. profundicola.
Morphology
A small ricefish with an upturned mouth and large eyes. FishBase gives a maximum of 2 in TL. Males have larger fins than females.
Habitat
Lake Matano, Central Sulawesi, Indonesia, a very deep tectonic lake with clear, alkaline, low-nutrient water. The species lives near the shore in shallow water among rocks and submerged plants. FishBase gives a pH range of 7.5 to 8.5 and a temperature range of 22 to 25 C. The lake is shared with a small number of other endemic ricefishes, shrimp and snails, and the type locality is east of Soroako.
Feeding
Takes small invertebrates and algae from the shoreline and surface water.
Mating
Courtship has not been described in detail.
Breeding
From aquarium observation reported by FishBase, females carry a cluster of about 15 to 20 eggs and deposit them among plants and floating objects. FishBase calls it a non-annual breeder. Incubation time has not been published.
In the aquarium
Occasionally available, but FishBase describes it as very difficult to maintain in aquaria. Use a planted tank with a lid, water in the pH 7.5 to 8.5 range and tropical temperatures that match Lake Matano. Feed small live and frozen foods, and keep it with other small peaceful fish or shrimp.
Conservation
The IUCN Red List classes Oryzias matanensis as Near Threatened, meaning it is close to qualifying for a threatened category. Lake Matano's endemic fauna is exposed to introduced fishes, nickel mining in the catchment, and development along the shore.