The golden otocinclus (Macrotocinclus affinis, formerly Otocinclus affinis) is one of the smallest known suckermouth catfish, often called a 'dwarf oto'. Endemic to Southeast Brazil, this herbivorous, rheophilic, bottom-feeder only grows to around 4 cm (1.6 in) in length. The close relatives of this small fish are often used for the purpose of controlling algae in small home aquariums, under the name Otocinclus affinis. In reality, they belong to the species O. vittatus, O. vestitus and O. macrospilus. The real M. affinis is not present in the aquarium hobby.