The world of 'Plecs' has expanded enormously in the last 20 years or so, so many people, and older books, are unaware of the many species and variety of Plecs -thinking there is just one Plec – The Common Plecostomus rather than the hundreds known today, from which the nickname 'Plec' or 'pleco' has come.
Plecs are a type of Catfish, often called Sucker mouth Catfish, they all belong to the family known as Loricariidae. Some of the Plecs do seem to 'suck' on the glass of the tank, or rocks etc, and have large sucker -like mouths which has given rise to this nickname.
There is a common misconception that all plecs eat algae and rubbish in the tank and are bought as tank cleaners and do not need feeding. This is simply NOT true. Some include algae and wood in their diet, but not all , some are herbivores, some omnivores and some are carnivore!, and they all do need food which is appropriate for them. So it is important if you own a plec , or are planning to get one, to know which type it is so it can be fed appropriately. Many are nocturnal and do a lot of their feeding at night and hide in dark places during the day, so they need hiding places in the tank such as bogwood/driftwood pieces or rock caves.
The various plecs differ in size and colour, from mottled brown to black and white stripes and spots as well as yellow, green, orange and red or even blue patterns. Some stay quite small (eg 1 inch long otos or 3-4 inch peckoltias) whilst others (including the common Plec) can grow to over a foot and need big aquariums to accommodate them. They have been grouped into families and given Latin names, and some have wonderful sounding common names, such as the zebra pleco, Golden nugget, blue phantom, royal whiptail, orange spotted Bristle nose, and so on. As there are too many to name the experts have tried to classify each species by giving them a unique number, the numbers start with a prefix of L or LDA and are known as the L-number. Just to be confusing some types that can vary in appearance ( perhaps from young to adult) have been accidentally given more than one L-number.
For more information about L-Numbers, check out the links below
Confused about L-numbers