Cfl dwc grown in rock wool and perlite

I have a major algae problem. My perlite is turning green on top. I think my environment is too suitable for plant life sometimes. Does anyone know a good way to get rid of this. It's too late to change the perlite out bc of my root system. Plant I 2 weeks from germ and already has 3 different roots about 8 inches out of the pot. No pun intended! Anyway, pleeeease help if you can.

Thanks for all of your help RIU!

I fixed it though just a quick reduction of perlite and then I covered the top with new rocks.