Hypostomus plecostomus, also known as the suckermouth catfish or the common pleco, is a tropical freshwater fish belonging to the armored catfish family (Loricariidae), named for the longitudinal rows of armor-like scutes that cover the upper parts of the head and body (the lower surface of head and abdomen is naked soft skin). Although the name Hypostomus plecostomus is often used to refer to common plecostomus sold in aquarium shops, most are actually members of other genera.
Suckermouth catfish are of little or no value as a food fish, although they are at least occasionally consumed over their native range. A demand exists for them, however, as a bottom cleaner in the aquarium trade.
A large variety of common names is used to describe H. plecostomus, where plecostomus and the shortened "pleco" are interchangeable in all common names. The names include:
Hypostomus plecostomus is one of many species of fish that is able to breathe air. Hypostomus plecostomus relies on its gills for respiration in normal and slightly hypoxic water, and the less oxygen present in the water, the more frequently it surfaces to breathe air. The air is taken to the stomach where the oxygen is absorbed, and the air can be kept in the stomach to increase buoyancy, which may help it to feed on vegetation.
This species' native range is tropical northeastern South America; it naturally occurs in northeastern Brazil, the Guianas, and Trinidad and Tobago. Confusingly, the name Hypostomus plecostomus (or Plecostomus plecostomus) has sometimes been incorrectly used for several more-or-less similar loricariid catfishes, both in the popular and scientific literature. For example, it has sometimes been suggested that it occurs in southern Central America, but this is an entirely separate species, Hemiancistrus aspidolepis (also known under another synonym, Hypostomus panamensis).
Some Loricariidae species have been widely introduced to several countries around the world and reported as H. plecostomus. It is erroneous, and the concerned species belong to the genus Pterygoplichthys (either P. pardalis, P. disjunctivus, P. anisitsi or P. multiradiatus). In the United States, a Pterygoplichthys species has been introduced to some regions in the South, most likely released by aquarists into the local waters. For example, they are present in a lake in the neighborhood of Hammock Trace Preserve in Melbourne, Florida. In Texas, reproducing populations occur in spring-influenced habitats of the San Antonio River (Bexar County), Comal Springs (Comal County), San Marcos River (Hays County), and San Felipe Creek (Val Verde County), as well as in drainage canals in the Rio Grande Valley and Houston.
The same identification issues have spread in the literature regarding the invasive catfishes in Taiwan, with H. plecostomus being one of the numerous names used to designate the species: DNA studies showed the alien fishes were actually P. pardalis and P. disjunctivus (that hybridise extensively).
H. plecostomus prefer to live in water between 72 and 86 degrees Fahrenheit (~22.2 to 30 degrees Celsius), with a pH between 6.5 and 7.5.
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, including newly hatched and baby golden apple snails as well as Malaysian trumpet snails. This omnivorous species also 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 in the wild, they can grow to be a maximum size of 50 centimetres (20 in). In captivity, however, a full-grown Hypostomus plecostomus only reaches 15 inches (38 cm) on average, which could be explained by the subpar oxygen levels in most home aquaria and other practices of bad fish husbandry. In the aquarium trade, 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.
