That is BBA and as far as getting rid of it..... Good luck. The reasons for it appearing are low co2, too much light, buildup of organics, and whatever else somebody wants to blame it in or a combination of all of them. Some kind of imbalance is the most straight forward answer. I have had it come and then disappear completely just to come back again. You can do a search for BBA and see all the threads that are started about this. You can spot treat with Excel or hydrogen peroxide and keep it from spreading.
All matter is merely energy condensed to a slow vibration, we are all one consciousness experimenting itself subjectively, there is no such thing as death life is only a dream which is an imagination of ourselves. Bill Hicks
ua hua's 90 gal.
ua hua's 5,000 gal. water garden