your fish store employee's are stupid... or should i say uneducated
next time you walk in there tell them its called cyano bacteria. the best way to beat it is
dont leave your lights on for so long (10hrs a day)
feed less
build up your clean up crew
buy products that remove phosphates such as phosban (phosphates are the food of algaes such as cyano)
also do larger, 15-20% water changes
also check out the archives, i believe it says how to get rid of cyano effectively in there