I ran into the same issue when I was cycling my tank. Started to have hair algae growing on my LR
and sand. I left the lights off and made sure the blinds were closed and that seemed to solve the issue. As for the CUC I added mine after a month when I figured out how to keep the Salinity stable. You want to make sure that there is something for them to clean up as well, so use your better judgement. Good luck!
Humanity is akin to the ocean, a few drops of dirty water will not cause it to loose its beauty.