Coptodon deckerti is a critically endangered species of fish in the cichlid family. It is endemic to Lake Ejagham in western Cameroon. It is threatened by pollution and sedimentation from human activities, and potentially also by large emissions of carbon dioxide (CO2) from the lake's bottom (compare Lake Nyos). A species of catfish from the genus Parauchenoglanis has recently been introduced to the lake, and this probably presents a serious threat to the endemic cichlids.