Otocinclus is a genus of catfish in the family Loricariidae native to South America which are commonly called "dwarf suckers" or "otos". This genus, like other loricariids is characterized by rows of armour plating covering the body, as well as the underslung suckermouth. They are generally small in size; O. tapirape is the smallest of the species (2.4 cm), while O. flexilis is the biggest (5.5 cm). These species have adaptations that allow them to breathe air. A duct forms at the junction between the esophagus and the stomach and expands into an enlarged, ring-like diverticulum, diagnostic of this genus, which allows air-breathing. Otocinclus are popular aquarium fish. They are often purchased as algae eaters. It is difficult to breed them in captivity, and only wild caught Otocinclus are