I know this thread is a couple months old, so you may have fixed your problem...
I just cleared up a BAD case of hair algae in a setup similar to yours. I added a sponge filter, overdosed excel for a few days, and STOPPED DOING WATER CHANGES.
The Fraternity of Dirt #41
SunSun Pimp #66
"In the end we will conserve only what we love. We will love only what we understand. We will understand only what we are taught." Baba Dioum