Nuisance algae ID

[BGJames]

Struggling to identify this algae. It originally started out as patches of brown, dust like algae on the sand bed and now it has stringy bits growing from it. Grows back quickly when I turn the sand bed over during maintenance. Tank is coming up to 6 months old and went through the 'ugly' stage but I did add an extra piece of small rock about a month ago. Running a skimmer and powerheads. Phosphate is roughly .03 on a Salifert kit and Nitrate is between 5 and 10, also Salifert.

Thanks in advance

 

[revhtree]

Do you have a photo?