Driftwood is expensive, just to let you know. We live near a lake, where there's tons of driftwood, but people tag a huge price tag!
He probably is eating, but you're not aware of it.
For our Pleco we bought: Hikari Tropical Sinking Wafers
We got them at Pet Supplies Plus, I think, but apparently you can get them at Petco, too.
Also, another thing you need to know about Plecos is that they can get HUGE. Some can grow up to 5 ft long.
I mean, chances are yours won't, ours definitely didn't, but just to warn you. They're awesome fish...we had a tank split, and gush 90 gallons of water all over the living room floor. Plecos are apparently strong enough swimmers that he fought against the current until the water drained all the way out. Not many fish could say they survived something like that. I heard another story of this guy's wife who walked into the living room and found her Pleco outside of the aquarium, with scratch marks and bitten fins(they had cats). She picked it up, thinking it was dead, and it started thrashing around. Unsure what else to do, she put it back in the tank and it lived for years longer. So...yeah, they're awesome fish. We got very attached to our Pleco.