Well it does look greener when the light is on.
I do have a slight problem in my DT - on both sides of my set up I have large window and doors with large windows. This is on the south side of the house. On the weekends when I am home I can see ambient light coming into the tanks, so much that the leather toadstool opens up when the sun is out and the DT lights are off. In these areas I have persistant algae, does not look like hair algae but short and really thick stuff. I was hoping over time with the AS and PS this would go away, but it hasn't. I am beginning to think that I should put some blinds on the window and doors. Although my Phos are low I think something is feeding this algae. I was thing thking of painting the sides of the tanks but I like to see through the ends.