I have a little of both, hair algea and gsp. The gsp really has taken off recently. I'd say another few months and it will cover the back glass, so that's nice. Looking over the top of the screen at the actual tank, I'm amazed that the picture is a week old and the GSP has probably spread another two inches up the glass. That stuff grows like crazy.
As for the algae, that's why I wanted some chaeto. My fuge has been off-line for a few months, and I'm starting to get algae real bad. Sooooooo, return to the fuge, get my lights back online and get some chaeto to try to suck up some nutrients. Next water change I'm going to scrape the back glass, and hopefully that goes a long way towards eliminating that scourge.
The tank is drilled but over flow boxes don't go all the way down. It was a non reef ready that Radone DIYed into reef ready and then sold to me.