Could the light be more subdued from the sun if possibly maybe placing something in back of the aquarium? or say a solid black background or something of those sorts?
YES! I got a suggestion to go to a framing store and buy backing, for the back of the tank (all black) and now I have blocked one of the sides too.
I just used black construction paper and taped it on. There's a big window a few feet behind the tank. The algae is still in the wings ready to go. I put non-metal sheeting material over my glass top. I''m also concerned that the windows at the other end of the room are driving the algae. Room-darkening shades should do the trick.