CarlD recommend polyquat to you in this thread and I asked if you'd considered it. You've probably read about it elsewhere as well.

Polyquat is an algecide but works best to prevent rather that kill algae. Polyquat also can act as a clarifier and should help clear the water. Keep a close watch of your FC if you do decide to use polyquat. As Watermom pointed out: the polyquat will create a chlorine demand and you don't want to start another algae bloom.