I would start by siphoning out as much as possible with airline tubing. Direct more flow over to that area. What are your params? How long are your lights on for? If it is cyano, nows the time to get it out. When i delt with it , it took 6 weeks to get rid of it! Also whats your water change schedule and source of water? So many questions....I feel like a therapist..lol...tell me about your childhood...lol