Taxonomy & naming
Smith described the species in 1945 from a small canal in Bangkok. The name is a Latin diminutive meaning very small, which describes the fish well. It is one of the smallest members of Oryzias and was a standard laboratory subject for studies of ricefish systematics.
Morphology
A tiny, transparent ricefish. FishBase gives a maximum of 1 in TL, and males show larger fins than females.
Habitat
Ponds, canals, ditches and rice paddies in Thailand, Cambodia, Laos, Vietnam and Malaysia, often in vegetated, still water. FishBase describes clear-water swamps and gives a pH range of 7.5 to 8.5 and a temperature range of 22 to 25 C.
Feeding
Takes the smallest zooplankton and insect larvae. In captivity it needs very small foods such as baby brine shrimp and microworms.
Mating
Males display close to a female with extended fins before spawning.
Breeding
Egg clusters are carried briefly at the vent and then deposited among fine plant material. FishBase reports it as a non-annual breeder. Incubation time has not been published.
In the aquarium
A fish for a small, quiet tank with fine plants, kept with similar-sized species or alone. It is easily lost in a community tank because larger fish eat it. A lid is needed.
Conservation
The IUCN Red List assessed Oryzias minutillus as Least Concern in 2007. It is widespread and common where its habitat of still, shallow water remains.