Brown algae? Or slim?

300 gallon preform. 3 months old. Temperature about 80. I have a brown
looking algae. I never had that before. The water is clear, the fish are
happy. I have 3 turtles all 5-6 inches. and a few fish. I have a great
filter with uv light. But the pump is 1600gph. So maybe its to fast
flowing for the 13 watt UV to work. Will it work at all at that flow?
The filter has
been working perfect. All the fish are very active the turtles eat and
bask. But I have this brownish looking algae on the sides of the preform
and all the plastic plants, rocks ect. I cant have live plants cause the
turtles eat them all.. If I move any rocks or the filter there is no
brown. So It must be algae from the sun. Anything that I move has no
algae unless its in the sun. Dark areas do not have it. . I used a good
bacteria since additive since I started. Is this good algae? Its browm
but never grows more than 1/16 inch. (like slime) It wipes off easy with
a towel. Thank you