Satanoperca

Satanoperca is a small genus of cichlids from South America, where they are known from the Orinoco, Essequibo, Nickerie, Amazon and Paraná–Paraguay river basins. They are mainly found in areas with slow-moving waters, but some species have also been recorded from rapids.

They are part of a group popularly known as eartheaters and feed by picking up mouthfuls of sand to sift out food items such as invertebrates, plant material and detritus (the only exception is mid-water feeding S. acuticeps). They often feed in small groups and one individual may act as a watchman, which will charge an approaching piranha with its mouth open and fins erected. The Satanoperca in the group take turn acting as watchman.