im not sure what caused it to start growing, my tank gets a few hours of sunlight in the morning ... thats about it, I just have the regular light,that came with the tank . It was weird, just like 2 weeks ago the algea started growing. I went out & got an algea scraper, and had been cleaning it off of everything ... i thought it was a bad thing ! I guess I'll just let it grow ... I was thinking,I might just clean it off of the very front, so I can still have a clear view of my fishies. Thanks for sending me that website, it was SO cool, I checked it out for awhile last night ...