seems like you need more flow, that or just point a powerhead/koralia if you have one up more towards the surface to agitate it a little and it should go away.
Oh-oh, just put my hand in front of the powerheads. Both have very little pressure. Maybe I need new ones or they might need to be cleaned. They were new 5 months ago.
what types? they more than likely need to be cleaned. take some vinegar and water mix it half and half and put them in it running overnight then rinse them really good after then pick the excess algae from them and they should be good as new.