The coppercheek darter (Nothonotus aquali) is a species of darter endemic to the southeastern United States. It is only known from the Duck River system of Tennessee. It is an inhabitant of small and medium rivers where it occurs in rocky riffles with clear, fast-flowing water. It preys on insect larvae and other immature stages and is also known to consume snails. This species can reach a length of 8 cm (3.1 in), though most only reach about 5.6 cm (2.2 in).