Red-eyed characin

Geographical Origin and Habitat: Arnoldichthys spilopterus is native to West Africa, specifically found in the coastal river basins of western Nigeria, including the Ogun and Niger rivers. It inhabits slow-moving rivers, forest streams, and shaded freshwater systems characterized by dense overhanging vegetation and leaf litter.

Taxonomy and Morphology: Belonging to the African tetra family Alestidae, this species is the sole member of its genus. It features an elongated, moderately compressed body covered with large, reflective scales. Adults can reach a maximum length of 8 to 10 centimeters, with females being notably deeper-bodied than males.

Social Behavior: It is a highly active, schooling fish that should be kept in groups of at least 6 to 8 individuals. Keeping them in smaller groups can lead to shyness or occasional fin-nipping out of stress. They occupy the middle and upper levels of the water column, requiring ample open swimming space.

Coloration and Sexual Dimorphism: The body is silvery with green and blue iridescence. A brilliant yellow-green stripe runs horizontally above a dark band along the flank. The upper half of the iris is bright red. Males possess colorful stripes of red, black, and yellow on their anal fin, whereas females have a simpler anal fin with a single black spot.

Aquarium Setup: A tank of at least 200 liters is recommended due to the active nature of this schooling species. The tank should be densely planted along the sides and back using hardy plants like Anubias and Microsorum, leaving the center open for swimming. Floating plants can help diffuse light, which makes the fish feel secure.

Diet and Feeding: In the wild, they feed primarily on insects and small invertebrates at the water surface. In captivity, they readily accept high-quality flakes and floating pellets. However, to maintain optimal health and coloration, their diet should be supplemented with live or frozen foods like bloodworms, brine shrimp, and daphnia.

Water Quality: Prefers soft, slightly acidic water but is highly adaptable to a wider range of parameters. Ideal water conditions include a temperature range of 23-27°C, pH of 6.0 to 7.5, and general hardness (GH) of 5 to 15 dGH. Good filtration and regular water changes are required to keep organic waste low.

Compatibility and Cohabitation: A peaceful species suitable for large community aquariums. It coexists well with other medium-sized African tetras, robust dwarf cichlids, Synodontis catfish, and active cyprinids. It should not be housed with very small fish or fry, as these may be perceived as prey due to the characin's mouth size.

Aquarium Breeding: Breeding is achievable in a separate, dimly lit spawning tank with soft (GH under 5), acidic water (pH 6.0-6.5) and spawning mops or fine-leaved plants. The parents are egg-scatterers and will eat their own eggs; they must be removed immediately after spawning. Fry hatch in 30 hours and require rotifers or infusoria.

Risks and Diseases: This is a resilient species with no specific disease susceptibilities. However, they can suffer from Ichthyophthirius (white spot disease) if exposed to sudden temperature drops or poor water quality. Maintaining stable parameters and a clean environment is the best prevention against bacterial and parasitic infections.