The Yellowstripe Cardinalfish, Ostorhinchus cyanosoma, is a small and slender reef dweller whose translucent to silvery body carries several yellow to orange horizontal stripes, accented by blue highlights around the eyes and gill covers. Adults reach roughly 2.8 inches, making this one of the more manageable schooling options for modest reef systems. The species occurs across the Indo-Pacific, including the Red Sea, with collection commonly out of Fiji and Indonesia. In nature it occupies sheltered clear-water lagoons and seaward reefs from about 1 to 49 meters, typically gathered in aggregations beneath ledges, inside holes, among branching Acropora and Pocillopora, or sheltering among the spines of long-spined sea urchins.

Adult housing begins at a 30-gallon aquarium, and larger volumes are worthwhile if the goal is a small group or shoal. Structure matters more than swimming room here: build generous live rock with caves, overhangs, and tight crevices, and consider branching corals, sea grass, or long-spined urchins as additional cover. This is a slow, methodical swimmer that relies on shelter to retreat into when startled, so open tanks without refuge tend to leave it withdrawn. Gentle to moderate flow suits it best. Because the species is nocturnal and spends much of the daylight period tucked away, a mature system with established rockwork gives it the confidence to emerge and forage.