So, recently some film algae decided to grow on my tank. There is excess nutrients in the water from something that has died. I don't know what died or where it died so I can't remove the source of the nutrients. I am constantly doing water changes every few days to help. The algae keeps growing on my glass. It's really hard to scrape. It's definitely not green coralline though. I have a plastic tank so scraping it with metal would scratch it. What should I do?

