It's not likely to have a major, negative, impact on algae or cyanobacteria growth. Even if we assume the product actually contains living bacteria, those bacteria would have to compete with the resident organisms for the same nutrients. (nitrate/phosphate) Your tank all ready contains the microbes described on the label of this product. Based on the conditions of your system, you will only be able to support a given number of these microbes. Adding more than your system can support will simply cause some to die. When dead bacteria, or any organic waste, rots, it releases nitrate and phosphate. He even claims that his product "enhances the rate of organic waste degradation." Which means it speeds up the rate of nitrate and phosphate production. When nitrate and phosphate levels rise, organisms like algae and cyano can grow more rapidly. IMHO, adding this product has a much higher likelihood of increasing your cyano problem. Not curing it.
