There are 19 species of freshwater fish in Sha Lo Tung, including the Hong Kong Paradise Fish (Macropodus hongkongensis), which has received the most attention as its distribution is limited to a small area in Hong Kong and south east Guangdong. It is regarded as a species of local concern by the Agriculture, Fisheries and Conservation Department.
Native freshwater fish are now threatened by alien fish species such as Gambusia affinis, Poecilia reticulata and Xiphophorus hellerii. These species grow quickly and take up large proportions of shelter and food, and are threatening the survival of the native freshwater fish species.