Hypostomus plecostomus is named for its sucker-like mouth, which allows it to adhere to a surface, as well as to hold and rasp at food. This omnivorous species feeds on algae, aquatic plants, and small crustaceans.
H. plecostomus is one of a number of species commonly referred to as "plecostomus" or "common pleco" by aquarists. These fish are sold when they are young and small, but they can grow to be a maximum size of 50 centimetres (20 in). In the aquarium, this dark-colored, bottom-feeding, nocturnal catfish is often purchased for its ability to clean algae from fish tanks but also contributes a lot of waste to the nitrogen cycle. They are difficult for other fish to harass, both due to the semi-aggressive nature of the fish as well as its thick armor.