Bingo.........The problem with plecos are as they grow, they do less and less algae eating....most are even canivorous, and will start eating the other fishes food and leave the algae alone......Prochilodus are amazingly good, I have one that cleans algae off of plants without harming any of the plant.
You can't go wrong with a Prochilodus (Flagtail)....non stop rasping on glass and everything else for algae....
Good luck