Common otocinclus

The common otocinclus is one of the most popular algae-eating catfish in the planted-tank hobby, valued for its peaceful disposition and efficient grazing on soft green algae and diatom films. It ranges across much of South America — from the Amazon and Orinoco basins through the Paraná and Tocantins drainages — where it inhabits slow-moving tributaries and floodplain lakes with dense vegetation. Adults reach about 3.3 cm in total length and are best maintained in groups of six or more in a tank no smaller than 60 litres. A well-established aquarium with mature surfaces, moderate lighting, and stable water parameters between 20–25°C and pH 6.0–7.5 suits them well. Their diet should be primarily herbivorous: blanched zucchini, cucumber, and algae-based wafers supplement what they graze from the tank. Otocinclus are sensitive to deteriorating water quality and should only be added to cycled, stable aquaria. They are entirely peaceful and do well with small tetras, rasboras, and dwarf shrimp, though they may be outcompeted for food by more aggressive grazers. The belly should remain rounded — a hollow or pinched belly indicates starvation, a common issue in underfed groups.