You can try playing with your photo-period some. It looks like you have a light running 8 hours? Might knock this down some and see if that helps. I would also put the light on a timer if it is not already. Increased plant load probably wouldn't hurt, though I doubt water-changes will do the trick (having had massive thread algea issues in the past myself). How is circulation in the tank?
When approaching algea problems, I almost always consider lighting issues first before chasing around other potential culprits.