my parameters are in check. i dont know for sure its been many years since i saw cyano. but i think i killed of my diatoms and it seg-wayed into cyano but during that i had a alk swing that ticked off my corals and i think a algae or bacteria problem is why they aren't coming back faster or even at all. im gonna post two pictures these are the best i can get to display what's going on there is some sort of red brown matte and i don't know what it is i assume cyano but i want some other opinions before i go treating it. If it is cyano can it negatively effect coral even if its dyeing off. i don'thave the token carpets of it on the rocks or sand bed so that's why im hesitant.