Fish atlas

Geographical Origin and Habitat: Sphaeramia nematoptera is widely distributed throughout the tropical waters of the Western Pacific, ranging from Indonesia, the Philippines, and Palau to the Great Barrier Reef of Australia and the Fiji Islands. This species resides in cohesive groups within protected lagoons and shallow coral reefs, at depths between 1 and 15 meters. It finds primary shelter among the dense branches of stony corals, particularly of the genus Porites, which shield it from strong ocean currents and open-water predators.

Taxonomy and Morphology: Belonging to the class Actinopterygii, order Kurtiformes, family Apogonidae, and genus Sphaeramia. It features a deep, laterally compressed body, two distinct and separate dorsal fins, and exceptionally large, bright red eyes, which are characteristic of fish with crepuscular and nocturnal habits. Adults grow to a maximum length of approximately 8.5 centimeters.

Social Behavior: It is an extremely peaceful, slow-moving, and gregarious species. During the day, these fish hover almost motionless in compact groups under the shade of branching corals, maintaining a stable social structure. At dusk, the school disperses to hunt for micro-crustaceans and zooplankton in the water column, regrouping at sunrise.

Coloration and Sexual Dimorphism: The coloration is unique and striking: the head and anterior body are greenish-yellow, the eyes are vivid red, a thick vertical black bar runs down the midsection under the first dorsal fin, and the posterior body is beige to silvery with reddish-brown polka dots. There is no visible external sexual dimorphism.

Aquarium Setup: Requires a marine reef aquarium with a minimum capacity of 100 liters. The setup must include live rock arranged to create shaded areas, caves, and overhangs. Water movement should be gentle to moderate, as this fish is a slow swimmer. The risk of jumping is low but present, so a covered tank or mesh lid is recommended.

Diet and Feeding: Primarily carnivorous. In captivity, it readily accepts high-quality frozen foods such as mysis shrimp, brine shrimp, finely chopped krill, and fish eggs. Over time, it easily adapts to small dry pellets or flakes enriched with vitamins. Feed 1-2 times daily, preferably in the evening when they are most active.

Water Quality: Water parameters must be kept stable: temperature between 23 °C and 27 °C, pH between 8.0 and 8.4, specific gravity (SG) between 1.020 and 1.025, and carbonate hardness (KH) between 8 and 12 dKH. Although it is more tolerant of minor nitrate fluctuations than other marine fish, sudden salinity swings must be avoided.

Compatibility and Cohabitation: It is 100% reef-safe and completely ignores corals and ornamental invertebrates. It is an ideal tankmate for other peaceful, small marine species. Avoid housing them with aggressive fish, fast-swimming competitors, or large predators that could stress or prey on them.

Aquarium Breeding: This species is a paternal mouthbrooder. Following a courtship ritual, the female releases an egg mass which the male collects and protects in his mouth for about two weeks, during which he does not feed. Rearing the tiny larvae requires live food cultures such as rotifers.

Risks and Diseases: This is a highly resilient and long-lived species. However, it can contract external parasites like Cryptocaryon irritans (marine ich) if subjected to thermal or chemical stress, and bacterial infections if its long, delicate fins are nipped by incompatible tankmates.