Sucker catfish

About

Found in the Laguna dos Patos drainage of southern Brazil, this small loricariid catfish, Otocinclus flexilis, is one of the lesser-known members of a genus that hobbyists have relied on for soft algae control for decades. Like its otocinclus relatives, it is a dedicated herbivore, spending most of its day methodically grazing surfaces clean. What sets the genus apart biologically is a facultative air-breathing ability, meaning individuals can supplement gill respiration by gulping air when oxygen levels drop. A handy adaptation for life in variable South American waterways. In the aquarium, this species behaves much as you would expect from an otocinclus: peaceful, busy, and almost constantly in motion across glass, leaves, and hardscape. One endearing habit is its tendency to park on the front glass, giving you a clear look at its flattened underside and the rasping mouth that does all the work. Topping out somewhere between one and a half to nearly three inches, it fits comfortably in modest setups. That said, otocinclus as a group are sensitive to poor water quality and do not handle the nitrogen spikes common in new tanks well, so this one is better suited to a keeper who already has a stable, established system running.