I have been having this problem myself lately. The best way I've found lately is 20% water changes twice a week and scrub the walls whenever algae shows up. Commercial products do not work in my experience and they can hurt fish. I haven't been able to keep plecos alive for long but while they lived they seemed to keep it under control but don't trust me on that last comment.
I had a problem about 2 years ago with a 50 gal tank that had hair algae and I could not keep a pleco alive in it either hmn??????????????? strange,
eventually I had to break the tank down, I let it dry out in the garage for a few weeks and just started over.
new gravel
boiling water in filter