Reddish brown algae growing on sand


Reefing newb
Hey guys have been in the saltwater hobby for about 2 months now.have had freshwater tanks all my not to new to the fish tank question is I have reddish brown algae growing on my sand how do I get rid of it..the tanks is 13.5 fluvial evo saltwater set up..also have a protein skimmer on it..