Identification and L-Numbers


Pleco, Plec, Plecostomus are all common names for a large family of ‘sucker mouth’ catfish that are popular amongst aquarists for their ability to clean algae of glass, plants and ornaments.  The term Pleco comes from an old name for the Common Plecostomus which used to be known as Hypostomus plecostomus, that name is no longer used but plecostomus has remained a common term to describe all catfish from the family Loricariidae, it is usually shortened to Pleco or sometimes just Plec.


The word is ‘CONFUSING’  Many of the plecos available to hobbyists are not yet fully classified by science or there is some doubt as to their correct classification. (Often even the scientists don’t agree how a particular fish should be classified) There are generally 3 ways to describe a pleco, its scientific name where known (family / subfamily – genus – species, e.g.. ‘Hypancistrus Zebra‘) its common name (usually the trade name under which it is sold and highly unreliable as it varies from company to company and country to country in this case ‘Zebra Pleco’ or “Royal Zebra Pleco’ or ‘Imperial Royal Zebra Pleco’) or its ‘L-number’ (L-046). L-Numbers were invented by a German tropical fish magazine (DATZ) in an effort to make the naming and identification of these fish easier, there are some 330+ L numbers described and while not always 100% accurate from publication to publication they are better than the highly confusing common names. The best source for identifying plecos I know of is the planet catfish web site.


L-Numbers are generally assigned depending on the location that a particular fish is caught (or is reported to have been caught) so it is very possible for the same fish caught in two different rivers to have two different L-Numbers, this is desirable because it allows the aquarist to duplicate the particular fishes requirements so as to give it the best chance or thriving. Some specimens are very adaptable and can be housed in just about any tank with no problems; others are considered ‘delicate’ and need particular conditions to do well. Unfortunately aquarists are forced to rely on the accuracy of the fish importer or their LFS as to which L-Number they are buying, but a bit of pre purchase homework on the internet can go a long way to confirming a fish has been labeled correctly.


If you are keeping the more common types of plecos that are bred in captivity then there is no real reason to narrow down a correct identification. IF however you are keeping a fish that has been caught in the wild then it is important to know what environment and more so what foods to provide for it. Despite looking similar there are a range of habitat and feeding requirements for the various types of pleco’s you can buy, and as all but the most common plecs are likely to be wild caught specimens it is good to have a rough idea of the requirements for your particular fish to avoid costly losses and a possible long wait for a replacement.


Planet Catfish Web Site – both the cat-e-log and the forums, lots of very knowledgeable people there.

Transfish Web Site – A German fish importer with an excellent section on L-Numbers.

Aqualog all L-Numbers 2nd Edition – An excellent book, containing almost all L-Numbers complete with photos.


Ancistrus – Hook, a reference to the hooked spines on the cheeks.
Baryancistrus – Bary = Heavy…   Heavy Ancistrus
Hypancistrus – Hyp = Under…
Hemiancistrus – Hemi = Half…  Half Ancistrus
Lasiancistrus – Lasi = Hairy…  Hairy Ancistrus
Megalancistrus – Megal = Great…  Great Ancistrus
Pseudancistrus – Pseudo = False…  False Ancistrus