Otocinclus, the dwarf suckermouth catfish, is a very popular algae-eating catfish. The seventeen species of Otocinclus (often called Otos) are very popular for algae control. Unlike their large cousins, the Plecos, Otos remain small and are not boisterous enough to cause damage to plants. Although they are often purchased singly for algae control, Otos are social and should not be kept in groups of less than three. They are native to South America east of the Andes mountains, in streams that drain into the Amazon, Orinoco, Paraguay/Parana rivers, and in streams that drain into the Atlantic in southeastern Brazil. They are notably absent from the Guianas.
Otos are small - they range in size from 16.5 to 43.8 mm (0.6 to 1.7 inches), not counting the tail. Females are 10-20% larger than males, and have a broader body, especially when they are in breeding condition. [Read the rest of my post at HubPages.com]