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Sri Lanka, one of the world's biological hotspots, exports wild-caught and farm-bred aquarium fish species to more than 70 countries. This study evaluated the potential for invasiveness of aquarium fish species now raised and traded in Sri Lanka's Gampaha, Kandy, and Polonnaruwa districts. A questionnaire survey of 40 hobbyists, 20 retailers and ten breeders of aquarium fish in each selected district was conducted to assess the causes of aquarium fish releases. The invasion potential was evaluated using a model consisting of species thermal tolerance, propagule pressure and invasion history. Overall, 59 non-native fish species belonging to 14 families (Acanthuridae, Callichthyidae, Characidae, Cichlidae, Cyprinidae, Helostomatidae, Loricariidae, Notopteridae, Pimelodidae, Poeciliidae, Osphronemidae, Osteoglossidae, Salmonidae, and Scombridae) were recorded from the aquarium trade in the country. Out of 17 species with high to moderate invasive potential, six have already been established in the environment in Sri Lanka. Therefore, Astronotus ocellatus, Barbonymus schwanenfeldii, Carassius auratus, Hypostomus plecostomus, Pangasianodon hypophthalmus, Poecilia latipinna, P. sphenops, Puntigrus tetrazona, Trichopodus microlepis, Xiphophorus helleri, and X. maculatus are identified as potential invaders in Sri Lanka. The reasons for the intentional release of aquarium fish into the environment were excessively large size, aggressiveness, diseases and high reproductive rates. The number of fish of each species released into the natural environment is positively correlated to the number kept in home aquaria. A well-coordinated institutional mechanism to control unwanted fish introductions through the aquarium fish trade in Sri Lanka is urgently needed. [ABSTRACT FROM AUTHOR]