It somewhat depends upon the algae, but even so, generally the glass is something you need to clean yourself. I use a sponge-type scraper and run over the inside of the front glass at every water change on all my tanks. I rarely see any algae, but it I don't do this every week, I sometimes will see the beginnings by the next.
A biofilm develops on all surfaces covered by water, and this is slimy/slippery if you run your finger across it, and it attracts algae along with microscopic critters and of course many types of bacteria. When I say "attracts," I mean that the biofilm is intended to support these various life-forms, so you are never going to eliminate it (nor should you want to). Even if fish or snails or shrimp ate some of the algae, the biofilom would still remain. You're better to give it a quick clean every water change.
Byron.