Morning All.
Right, your common pleco is a funny creature.
Basically, whilst under 6" their pretty shy and retiring and eat algae, shelled peas, blanched green leaves, zuccinis etc... they do carp a lot, which is a pain, but other then that, their really hard working fish at cleaning a tank of algae and uneaten food.
Once you've got a monster (7"+) after a few months (depending on diet, tank size etc etc) their taste change to a meatier diet.
I feed mine very little veg nowadays as he shows no interest in the stuff. he will simply patrol the surface at feeding time and wolf down some pellets, and as a treat i throw him a frozen silver side ever week or so.
Takes about a year or so til the hit the 12" mark, then growth really slows.
Had mine about 7 years on and off (actually was on of the first fish i bought) and hes only just pushing 14"
Best of luck
Craggy