hey i have a 75 gal tank and 25 gal sump and a i have a green hair algae i have used many staff and is not helping at all i do water change 15% weekly i have been using a nopox 10 ml per day but my no3 still high i test my water with a salifert test kit and no3 showing about 50 ppm and po4 is near 0 i need help i feed less and my light 4 to 6 hours per day i dont know what should i do