From what I have read, only the bristlenose pleco (of the commonly available varieties) minds its own business as it usually stays small and hence can find enough food in the tank.
The common pleco will grow too large and eventually attack your discus as their slimecoats make good food for them.
Consider Otos or Siamese algae eaters as alternate options. Though even with them you have to keep a watch & if they take a liking to the discus slime, remove them.