With over 650 species in the family, Loricariidaes, more commonly known as Plecostomus, are one of the largest families of fish known to science, and by far the largest group of catfish. Plecos are also one of the most popular species of freshwater fish, known for their love of algae and distinct personalities. But with so many species available, identifying your pleco can be a difficult task, especially due to the somewhat complicated naming system given to these fish.
Familiarise yourself with the most common species of Plecostomus, such as the common, bristlenose, zebra, sailfin, spotted and clown pleco. Being able to quickly and easily recognise these fish and their features will help eliminate most identity problems. Also be sure to note which of the common species can have colour morphs, such as albino variants.
Learn how the L-number system works for cataloguing Plecostomus. Since all plecos are a part of the Loricariidae family, importers began giving new species a number designation following an L (for Loricariidae) to identify them before science described them in more detail. Unfortunately, there is a good deal of confusion over L-numbers, because although many species have since been given scientific and common names, many hobbyists still refer to the fish by L-number. Additionally, for a time ,some L-numbers were recycled after a particular fish was renamed. The common Plecostomus, for example, is referred to as both L021 and L023.
Ask a reliable local hobbyist, or join a Plecostomus club online. Posting pictures of your fish on online forums is a great way to learn about the type of pleco you have, and many experts are more than willing to help someone less experienced in identifying their fish.
Understand that sometimes there may be no 100% reliable way to determine the exact type of fish you have, especially if the animal is imported or purchased from a speciality shop. Your best bet in these situations is to try and find out as much as you can on similar species, and base your care requirements from there.