I wish I hadn't given away my copy of David Boruchowitz's Simple Guide to the Freshwater Aquarium.
In that books, he suggests exactly as Meds081603 had recommended, except you don't need to add food. Just put some rocks in the bowl and put it in sunlight. Algae spores are everywhere, so you should have algae soon.
I actually don't know if you can predict what kind of algae will grow. Why not just give it a try? If you get blue-green algae you can always discard it.
I'm sure the plecos will benefit from the variety.