I have had clown plecos for a long while. They never go for any wafers. Clown Plecos are shy and not really outgoing. They mainly eat majority off the driftwood. SOMETIMES they've been seen on shrimp pellets and they tend to like the stem ends off of Zucchini. They love wood.
This is a list of vegetables and fruit that are popular with most plecs.
Butternut Squash+ other squash
Capsicum/Bell pepper(not the hot ones)
Mushroom (common plecs and goldspots love mushroom)let it float,they will reach it.
ones upon a time there was a small wild caught pleco that didn't recognise the food it was given. "what is a wafer"
To be serious : It will have to adapt, don't forget frozen / protein part of the diet as also the need of wood / cellulose for digestion.
As I believe @bizaliz3 stated : Plecos is a name for an enormous variaty of catfish, with all kind of different diets / needs. Some are 100% herbivores, some omnivores at the herbivorious side some at the carnivorious side and a few are mainly carnivorious / pescivorious.