mine would bully the corydoras, but only around the algea pelets that i used to throw in for him. he ruled his little cave and didnt let anybody through it, but only when there was food in it. when there was no food, everytone was allowed to come and go as they pleased (even though my angel wont fit through it anymore...). one day though, he just stopped bossing the corydoras around, and i knew something was off. and then he passed away two days later. there probably wasnt enough O2 in the water for him considering that he was wild caught in a pretty fast flowing river.
when your rubberlip isnt aggressive around food, there is something wrong. or when they dont run from you when you come up to the glass or turn the light on. rubberlips dont like either. mine was a pretty good algea eater. he always had bright yellow stripes after a water change.
im not really a pleco person, but he was pretty cool. i wouldnt put one in your tank though.