I know people who tout plecos as algae eaters, but personally, I would never buy a pleco for the purpose of being an algae eater. They may eat it, but they aren't very efficient at it, and will only eat it if there's nothing left! My clown pleco will occasionally eat algae, but for the most part, he's munching on my driftwood. I have 3 otocinclus to keep the algae in check.
Plecos are just great fish and get along with just about everything, that's why I love them. But get another algae eater if you want the tank clean.
38 Gallon (Freshwater): 1 Green Swordtail, 3 Yo-Yo Loaches, 1 Clown Pleco, 1 Blue Gourami, 4 Otocinclus, 7 Cherry Barbs.
46 Gallon (Saltwater): 60 pounds Lalo Live Rock, 60 pounds aragonite sand, 1 Coral Beauty Angelfish, 1 Peppermint Shrimp, 1 Mushroom Coral, 1 Emerald Crab, various snails and hermit crabs.
10 Gallon (Saltwater quarantine):