Otocinclus affinis

About

Found in coastal drainages near Rio de Janeiro, Brazil, this small otocinclus relative, Macrotocinclus affinis, is one of the more compact suckermouth catfish you can keep, rarely exceeding two inches as an adult. It shares the classic otocinclus body plan. A streamlined, armored frame with a sucker mouth designed for grazing biofilm and soft algae off hard surfaces. What makes it a bit of a character in the aquarium is its tendency to park itself right on the front glass, giving you a close-up view of its undersides and the rhythmic motion of that busy little mouth. Mainly nocturnal by nature, it can be seen resting motionless for long stretches and then bolting suddenly if something startles it. Like most fish in this group, it does noticeably better when kept in a group of five or more rather than solo. They seem to settle in and behave more naturally with company around. An established tank with a good coating of natural algae growth suits it best, as it grazes more or less constantly. It also has a facultative air-breathing capability shared across the genus, a handy adaptation for life in oxygen-variable South American waters. A rewarding little catfish for a keeper who already understands the basics.