Oryzias eversi

Adult Oryzias eversi reach a length of approximately 4 cm. The appearance of these fish is similar to other members of the genus "Oryzias". Males exhibit more intense body coloration, and their dorsal and anal fins appear larger and have elongated rays. Females, in contrast, have a silvery hue, and their fins are much more modest in size. Otherwise, they retain the characteristic features of all Oryzias.

Its natural habitat is located in Southeast Asia, where this species is endemic to the Indonesian island of Sulawesi, found exclusively in its southern regions. Here, Oryzias eversi inhabits small rivers and streams flowing through tropical forests. The water in these bodies of water is clean and clear, and its temperature remains stable and relatively low throughout the year. The flora is predominantly algae, attaching to rocky surfaces.

This is a peaceful schooling fish. It is recommended to keep Oryzias eversi in a group with its conspecifics, while avoiding cohabitation with other related Oryzias to prevent the appearance of hybrid offspring. They get along well with other calm fish species of comparable size.

Thanks to their modest size, a school of Oryzias eversi feels comfortable in an aquarium of 60 liters or more. The tank's decor is not critically important, and the aquarist can choose decorative elements at their discretion. Nevertheless, the fish will look most harmonious in an environment that mimics its natural habitat. The use of a sandy substrate with interspersed stones, several snags, and live plants is recommended. To add more naturalness, fallen dry leaves, such as Indian almond or oak leaves, can be added. Maintaining high water quality is a key condition for the successful keeping of this species. Since the fish live in flowing waters, they are extremely sensitive to the accumulation of organic waste. Therefore, the aquarium must be equipped with a powerful filtration system. In addition, weekly changes of 20–30% of the water volume with fresh water and regular cleaning are required. In general, the care for these fish is comparable to the care for other species.

This species does not have special dietary requirements, readily accepting a variety of appropriately sized foods, whether dry, frozen, or live. To maintain proper health, it is advisable to provide the fish with a varied menu, including, for example, flakes or granules in combination with small bloodworms or brine shrimp.

Breeding this species is not difficult: it is enough to keep males and females together. A distinctive feature of Oryzias eversi, like its relatives, is an unusual method of carrying offspring. The female lays 20 to 30 eggs, which she then carries attached by thin threads in a cluster near her anal fin. The incubation period lasts approximately 18–19 days. During this time, the female tries to hide among dense vegetation to ensure maximum safety for the eggs. After the fry hatch, parental instincts weaken, and there is a risk that adult fish may eat their offspring. To increase the survival rate of the fry, it is recommended to move them to a separate tank.

The fish are hardy and undemanding. Diseases usually manifest only with a significant deterioration in keeping conditions. In a balanced aquarium ecosystem, health problems are generally absent.

When choosing Oryzias eversi, preference should be given to active individuals that stay in a school and do not have visible damage to their fins or skin. It is important to ensure that the fish show natural curiosity and do not look emaciated, as this species is sensitive to water quality and transport conditions. In the store, pay attention to the cleanliness of the aquarium and the absence of dead fish in neighboring tanks to rule out the risk of purchasing sick individuals. Since the species is rare, it is recommended to ask the seller about the origin of the fish and its current keeping conditions.