Just a guess but I dont think its cyano... I think you have a diatom bloom. If you say that your tank as been set up for 6 months is a bit odd to see this happen now. Its usually more common to new tank set ups and will go away in a few weeks after the cycle completes. If I am indeed wrong and its a red colored mat with wavy hair growing off it then my apologies, cyano it is. Are there any fish in the tank? How is your flow? and do you use RO water for your changes?