If you dont have inverts in this tank, you can try API algaefix. Puts stress on fish so dose it to only the reccomended amounts for 3 days in a row, and during each dose dont dump it all in, slowly add it over the course of 1-2 hours. Helps the fish cope with it. Any sign of stress, do a water change.
Otherwise, you can blackout. That will hurt the algae. Once the issue is gone, add more plants and get Co2 right.