Hypostomus plecostomus (known colloquially as a ‘sucker fish’) is the scientific name for a type of freshwater tropical and sub-tropical Central and South American fish belonging to the family Loricariidae. They are large algae eaters, and to differentiate them from small algae eaters, they are often referred to as Plecostomus, often abbreviated as plecos or plecs

Loricariidae is the largest family of catfish, with almost 700 species and new species being described each year. These fish are noted for the covering of bony overlapping plates covering their bodies and a sucker mouth, and are therefore  often called sucker-mouth armoured catfishes. Most species are found in swift-flowing streams from the lowlands. They can also be found in a variety of other freshwater environments such as torrential mountain rivers, quiet brackish estuaries, black acidic waters, and even in subterranean habitats. This family has extremely variable colour patterns, body shapes, and can range from 1 inch in some dwarf species to over 30 inches in larger species such as Panaque.

The sucker-mouth exhibited by these catfish allow them to adhere to objects in their habitats, even in fast-flowing waters. The mouth and teeth also are adapted to feed on a variety of foods such as algae, invertebrates, and detritus. Some species, notably the Panaque, are known for their ability to digest wood. Most species of Loricariids are nocturnal animals. Some species are territorial, while others, such as Otocinclus, prefer to live in groups. Air breathing is well known among many loricariids. The ability to breathe air is dependent on the risk of hypoxia faced by a species; torrent-dwelling species tend to have no ability to breathe air, while low-land, pool-dwelling species such as those of Hypostomus have a great ability to breathe air. Loricariids exhibit a wide range of reproductive strategies, including cavity spawning, attachment of eggs on the underside of rocks, and egg-carrying. Parental care is usually well-developed and the male guards the eggs and sometimes the larvae. The eggs usually will hatch between 4 and 20 days, depending on the species.


While these fish are often purchased because of their algae-eating habits, this role may not be carried out. Most species are in fact detritivores. Instead, these days a great many species of Loricariids are sold for their ornamental qualities, representing many body shapes and colors.

Most species of Loricariids are nocturnal and will shy away from bright light, appreciating some sort of cover to hide under throughout the day. As they often originate from habitats with fast-moving water, filtration should be vigorous.

The study of this species is complicated. Some types of loricariids are often referred to by their ‘L-number’; this has been become common since imports of loricariid catfish fromSouth Americaoften include specimens that had not been taxonomically described. Currently L-numbers are used not only by fish-keeping enthusiasts but by biologists, since they represent a useful stopgap until a new species of fish is given a full taxonomic name.

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