Plecos are one of the best algae eaters for the glass and for certain plants but they will completely tear up amazon swords in particular, even very small plecos. They're really good on anubias, better than Amano shrimp.
I keep them until they get too big and trade out for smaller ones at the lfs. Biggest I've had is about 8-9 inches in a 55 or 75 gal, but no amazon swords in those tanks.
It's fun having someone studying your tank really close and suddenly jump back when a big one comes out from hiding.