they make pleco wafers, also as a treat can use a mettle clip to drop vegies down for him. mine eat what ever does not get eaten from the other fish and wafers. 12" and 16" , years old and not looking to die any time soon.
Common plecos tend to like meaty foods...maybe shrimp pellets. Most of my commons over the years ignored driftwood(I always try to have some anyways). Veggies were are always a hit or miss(mostly miss for me).
I feed my L91's and L333 whatever my cichlids eat, hikari and xtreme cichlid pellets and blood worms. also I feed the xtreme pleco pellets a couple times a week. I break those in half so they sink right away