Hi guys newbie here, I have a 40gal freshwater moderately planted tank doing well 6 months running. Last night I noticed brown and green hairlike algae on the outflow of my HOB. The HOB is located close to the light so i'm assuming it has something to do with it. I don't find algae growing anywhere else in the tank. I do add flourish once a week and excel daily, Ammonia test shows 0 and I do not do test for nitrite or nitrate. Is there any cause for concern?? thx in advance for any input..