It is better to decrease the intensity of the lights compared to shortening the photo-period. Shorter photo-period can/will still cause issues.
What I do is place some egg create over the tank, and then place some window screening on top of that. Assuming that your sig is right about your lights, I would use 3 layers and remove one layer each 5-7 days.
Since you are in Naperville (( I am in Lombard )) you are more then welcome to pick up some of my extra screening.