Cyanobacteria reproduces asexually by cell division, the addition of nitrogen gas, phosphates,nitrates, and lighting will feed the bacteria. They are caused by an accumulation of nutrients and biological imbalance from the result of poor filtration, over feeding, or high bio load. Cyanobacteria have even been known to enter the aquarium as spores. Bulbs with the correct spectrum promote growth of beneficial algae that will inhibit slime algae. (Remember that bulbs can lose their spectrum in as little as six months.) The second is to make sure there is adequate filtration. A protein skimmer is highly recommended along with enough water flow to prevent stagnant areas. The third is to keep the water quality exceptional. Finally, unfiltered tap water is highly discouraged. I went threw my log book last night. I did a lot of research when I had this problem.