Discolored algae

[ReeferCub]

Hi,

I use a HOG 1.x ATS. I am getting this discolored algae.
I run the ATS lights for 18 hours a day in 2 equal segments.
Is this discoloration due to excess lights? I have tried using the black cloth, that slows down the algae growth and I do not like that. Is this discoloration of algae a problem? Will this harm my tank?

Here is the photo:

 

[DereksReef77]

My guess is that you don't have enough nutrients in the water anymore. Consuming more than you are feeding, try cutting down the number of hours of operation. Go an hour at a time.