well, it's a nutrient issue, so water changes, vacuuming out what you can with each one is the best defense. cut back on feeding...etc.
if you are frazzled and can't seem to get a handle on it you can use a product called chemiclean by boyd enterprises. it worked well for me on more than one occasion. ultimately, the cyano will eventually resurface if some changes in husbandry aren't implemented.