Are plecos actually Catfish or are they just a relative?

[Nim Dibbley]

Sorry man, But what's 'AFAIK'?

as far as i know

 

[Peacock Rey]

Yes Plecos are actually catfishes.

 

[ElectricBlueSeanBurch]

AFAIK the name "pleco" originated from Hypostomus plecostomus and evolved into a slang term covering all sucker-mouth catfish (ie Loricariidae). You could possibly consider there to be only one true "pleco", but as it isn't a scientific term there are no conventions governing its use it can be used as loosely as one likes.

There is more than 1 hypostomus species, so you couldn't consider them all to be the "1" true pleco species...

 

[David R]

There is more than 1 hypostomus species, so you couldn't consider them all to be the "1" true pleco species...

If you like, although "pleco" is just an abbreviated form of plecostomus. There isn't really a right or wrong as it's just a nickname.