The Nile Tilapia (Oreochromis niloticus), known locally as තිලාපියා (Tilapia), is an introduced freshwater cichlid species in Sri Lanka belonging to the family Cichlidae. Native to Africa and the Levant, it was introduced to Sri Lanka in 1956 to expand commercial inland capture fisheries and aquaculture, quickly becoming one of the most economically critical food fishes across the island’s reservoirs and tanks. It is characterized by a deep, laterally compressed body, a single long dorsal fin with strong anterior spines, and a diagnostic pattern of distinct, regular dark vertical bars running along the caudal (tail) fin. During the breeding season, males undergo visual transformations, taking on a pronounced reddish hue along their body, head, and fin margins. As a maternal mouthbrooder, females hold the eggs and young fry inside their oral cavity to protect them from predators. Widely distributed across both the wet and dry zones of Sri Lanka, this highly adaptable species feeds predominantly on phytoplankton, algae, and organic detritus, maintaining dense populations that heavily dominate modified aquatic ecosystems.