I have a 29 gal tank. It has been set up for about two years. It is a community tank.It started growing a whitish, cottagecheese like algae. It started on the glass, looked like it was growing roots, it spread fast, a six inch diameter blob overnight. I scrape it off and it moves to a different part of the tank the next day. The fish are not affected at all. It creeps across the gravel and then dies in about 24 hours. I have done tank changes, scrubbed my plastic and fibre plants as well as decorative rocks. I can't seem to get rid of it. I've replaced filters checked my chemicals and everything seems fine. Someone help me please !!!thank you