It depends what sort of pleco they are and how aggressive/territorial they get and how big the tank is. Planet catfish is great for info on plecs, we have a few in our tank they are very young and will grow up together hopefully to avoid any problems when they get bigger. We have an L001, L240 and a chococolate ancistrus in a 300L If there are two male plecs especially of the same type they will need rom to establish territories and might spar a bit but I have read of people on here keeping them successfully. Good luck