As the name implies, this is a spiny fish, but it also possesses serrations on the scales. All members of this genus are spiny by nature, making them difficult to handle. There are probably about 12 species in the genus (the number is unclear, as some have not been described and are currently referred to only by their “L” numbers). Of the described species, P. leopardus (Leopard Plec), from the Rio Negro area in Brazil, is one of the few other Pseudacanthicus that are fairly regularly available.
There are only some half a dozen species in the genus Panaque, of which two—Emperor Panaque and the black-bodied P. suttoni (Blue-eyed Plec, Pleco, or Panaque) from northern South America—are regularly available. Distinguished by their large heads, sloping foreheads, and beautiful eyes, panaques make interesting additions to appropriately furnished and maintained aquaria.
Along with the black-spotted Liposarcus multiradiatus from the Amazon basin, Bolivia, Paraguay, and Peru, the white-spotted Snow King Plec is the most widely available species in the genus. This is largely as a result of large-scale breeding of the species (predominantly in Floridian ornamental fish farms).
This beautifully spotted species is one of the few species of Hypostomus (other than H. plecostomus) regularly available in shops. It is somewhat smaller than H. plecostomus, making it a little easier to accommodate. Its body coloration is generally brown or gray with darker brown spots.
Even today, over 240 years after this species was first described (as Plecostomus rather than Hypostomus), confusion still exists about its name, or even the correct identity of plecos available to aquarists under the name Hypostomus plecostomus. The generic name Hypostomus did not appear until 1803, yet—for reasons that are unclear—it replaced Plecostomus. Despite this, aquarists around the world have traditionally referred to H. plecostomus and the other Hypostomus species as plecos or plecs, thus heightening the confusion. Hypostomus species, of which there are more than 100, are distinguished from their closest relatives in the genera Glyptoperichthys and Liposarcus in several ways. The most distinguishable feature is the small number of dorsal-fin rays (seven) possessed by Hypostomus. Of the numerous species in the genus, very few are ever available within the hobby; H. plecostomus is one of them. At least two commercially produced varieties—an albino and a piebald — are occasionally available.
The Zebra Pleco, spectacularly patterned in black and white (as its name suggests), is a relatively recent introduction into the hobby. For a time it was known only by its “L” number (L46) until it was officially described and named in 1991 . Although once rare, it is now readily available.
This species still appears under its former scientific name in many aquarium books. However, the genus Pterygoplichthys is no longer valid, having been replaced by two genera, Glyptoperichthys and Liposarcus. The common name of pleco is also applied to species of the genus Hypostomus, from which Glyptoperichthys is easily distinguished by its dorsal fin, which has more than ten rays; Hypostomus has only seven.