Sometimes you will find although getting better flow, and fixing possible issues, it will still keep growing.
I had a start of cyano in my tank and tried fixing the common issues,but by the time I figured the hell with this and got ready to get some product against it, it was already crawling over some expensive zoas, and making them shut down. I got myself a product called ultra life red slime remover and dosed less than recommended since I was worried it could impact my tank....as promised in 2 days it was all gone. It makes the skimmer over react but besides that that was it. After the 48 hr I changed 20 percent of the water and the tank was just like before the algae issue. Since I didn't get rid of the problem earlier, some zoas attacked are now open, but loss some color. All other corals were indifferent. I believe adding chemicals to a reef tank is the last resort, and got this med because I was guaranteed by the top end LFS owner who is a food friend of mine as being safe...don't play with red slime, it will crash your tank if you don't eradicate it soon...seems like its already crawling all over your substrate....good luck