Probably - I would feed 1/2 an algae wafer daily, at least. Depending on the age of the tank, you may not have enough (or any!) algae for him to graze on.
Other good things to feed are zucchini, cucumber, yellow squash, and dark leaf lettuce. Lots of other things you can try such as sweet potato and spinach, but these first four are the least problematic and most readily accepted, IME. If the seeds bother you on the cukes or squash just scoop them out.
Feed the cuke and lettuce fresh. Everything else I would nuke in the microwave to make it a little softer (10-30 seconds depending on how big a slice). To get them to sink, I impale the veg with a bamboo BBQ skewer and then weigh down the skewer with a heavy plastic clamp. Other people use forks, some use rubber bands and rocks...just find what works for you
Lastly, look in the Asian section of your grocery store for plain sushi Nori. I clip on strips of this with a plastic clothespin (which sinks, unlike the wooden ones) and all the fish - including plecos - like nibbling at it.