Truth is, the "tank cleaner" thing is a myth. While plecos do feed on algae by sifting with their sucker-like mouths, they don't actually "clean" anything. In fact they poop like the dickens, so you better have a real good filtration system if you get one. Also they grow much bigger (which pet shops won't tell you), requiring very large tanks to live healthily.
All things said, Pleco is cute and I want to feed her algae wafers.