Not unless the Plec isn't digesting the food properly, even then other fish will only eat the good bits in it.
Plecs are IME the dirtiest fish in terms of waste. I'm afraid you're looking at regular vacuuming of the substrate. I reckon two or three times a week with a Plec that size.
Is he a Common Plec? If so, he will end up at least twice his current size so I hope you have a nice big tank for him