[das04j]

i have a brown stringy and short brown algae on my sand and cant seem to get it under control. Its so ugly and everytime i stir it up, its back the next day? I may have to do a water change later in the week. I just did a top off. so i am going to give it a day to adjust.
parameters

Ca-400ppm
alk- 10 dKh
nitrites-0
nitrates-15ppm
pH-8.5
salinity- 1.023
phophates- 0ppm