Panaque (Panaque nigrolineatus)

Their main demand is for a mixed diet including green algae, fresh vegetables such as carrots, courgettes, and spinach, and clean bogwood. In the wild, this pet fish feeds almost entirely on wood and algae.

The genus Panaque contains a small number of small to medium sized South American armoured catfishes that are notable for being among the very few vertebrates that feed extensively on wood. In addition, algae and aufwuchs are an important part of the diet, and they use their rasping teeth to scrape this from rocks. These algae eater fish are also popular aquarium fish, where the sound of scraping as these fish forage for food is easily audible.

Distribution and habitat
Panaque are found in the Magdalena River, Orinoco River, Amazon River, Essequibo River, and Lake Maracaibo drainages. All Panaque come from tropical South American and inhabit fast-flowing streams and rivers. They are weak swimmers but like other armoured catfish possess a strong sucker-like mouth with which they can hold on to submerged rocks and wood.

Physical characteristics
Mouth and teeth of Panaque nigrolineatus like other members of the armoured catfish family (Loricariidae), all Panaque have sturdy, armoured bodies covered in toughened plates of skin called scutes. These are not scales; like all catfish, Panaque lack scales. As well their armour, these algae eater fish have very sturdy dorsal and pectoral fin spines. They use these defensively, either to wedge themselves into cracks from which predators cannot pull them, or else to prevent large predators from swallowing them. Another characteristic typical of the armoured catfish family is an iris. Most fish are unable to regulate the amount of light that enters the eye since they have irises that cannot change size. Both male and female Panaque develop bristles, known as odontodes, on the side of head immediately before and onto the pectoral fins.

Unlike predatory catfish, these vegetarian catfish have very short barbels. These barbels can be seen in the photograph of mouth of a Panaque shown here; they are the short pointed structures on either side of a suckermouth. This sucker-like mouth allows them to attach to rocks and remain stationary with very little expenditure of energy.

Along with the species of the Hypostomus cochliodon group (formerly the genus Cochliodon), Panaque are the only fish that consume wood. These fish have particular adaptations to its wood diet include spoon-shaped, scraper-like teeth and highly angled jaws to chisel wood. There are also symbiotic gut bacteria that allow the fish to digest the wood.

Pet fish care
Several species of Panaque have become popular pet fish, in particular the brightly coloured Panaque nigrolineatus. The pets fish is known as the "royal panaque" or "royal plec", a reflection of its costliness and beauty when compared with the common plecs, Hypostomus spp. widely sold to aquarists as algae eater fish. Royal plecs have a greyish-green background colour against which are set thick, dark bluish-black stripes. The fins are edged with gold or cream, and the eyes are red. In captivity, royal plecs typically grow to around 30 cm in length.

A second species, Panaque cochliodon, is familiar to many aquarists as the blue-eyed plec. This pet fish was quite widely traded in the late 1980s and early 1990s but is now only rarely exported from its native Colombia. Aquarium books often refer to the blue-eyed plec as Panaque suttonorum or Panaque suttoni, though Panaque suttonorum is in fact a quite different fish that only comes from Venezuela. Blue-eyed plecs reach a similar size to royal plecs, but because many specimens are infected with a bacterium closely related to Rickettsia, mortality immediately after import can be high. Once settled in and feeding, they are no more difficult to keep than royal plecs.

All Panaque catfish require much the same thing in captivity. Their main demand is for a mixed diet including green algae, fresh vegetables such as carrots, courgettes, and spinach, and clean bogwood. In the wild, these fish feed almost entirely on wood and algae, and the meaty foods enjoyed by other plecs are not required. Because they are relatively large for aquarium fish and produce an unusual amount of waste, a big tank with a good filter is essential. Royal panaques at least are adaptable as far as water chemistry goes and though they prefer somewhat soft, slightly acid water conditions, they will tolerate hard, alkaline water as well.

In terms of behaviour, the pets fish are peaceful and nocturnal, and make good residents in community tanks. Like most of the other armoured catfish, they are territorial, and groups should only be kept in very large tanks.

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