algae growing on my rockwool cubes

so this morning i went into my room and found algae on top on my rockwool cubes. just wornding how to get ride of this? I pulled it off the top but you can still see alittle green. the cubes are 6'' and the clones have been in them for 2 1/2 weeks. I have a little nut burn on 4 of the 16 clones I have in there so I will be doing a water change and flush tomorrow. is there anything I should add for the algae to get rid of it?

The reason it grew on these i think is because the cubes are having a problem drying out and all the light they get. I was watering every two days then went to everyday but now back to every two days again. I'm also watering for 7 mins, should I cut that down a few mins? I will post pics in a few hours thanks for any help!

Two things you can do:
1: Cover the rockwool with visqueen or other opaque plastic, and the algae will die.
2: Buy some BioCat and add it to your nutrient solution wrapped in a cheesecloth. (that's what I use, and it kills algae dead, fast.)