Algae Problem

[elmo666]

Morning. Have a problem with a new set up. 300ltr aqua one, twin t5's, Aqua-gro nutra soil substrate. After filling, aquascaping and planting, despite instructions saying not to rinse, very fine brown dust everywhere. Did a fishless cycle, mature media in both filters, as substrate initially releases ammonia. All water parameters now normal. Tried repeatedly brushing off dust over last 3 weeks with a paint brush and siphoning when water changing, but its that fine its hard to shift. Plants are mainly various annubias and swords. Last few days its turned to an algae on the leaves only, comes away easily enough when rubbed, but makes a right mess. Not sure how to get rid of this. Lights on initially for 6 hrs as per the tropica app guidelines. Don't know if its down to the nutrient rich dust on the leaves or something else. Doing my nut in as tank is ready to move discus and their buddies into from my other tank. Any advice please?