Cyano. many threads and many methods to get rid of it. Don't stress its just part of reefing. Usually means your phosphates are high. I usually just vacuum it out until it goes away. You can try red slime remover but it will probably come back. Also I've done lights out for 3 days.
Vacuum out what you can, increase flow, reduce phosphates, and maybe add a fighting conch. That is about it. Red slime remover only treats the the visual and not the source, so it will eventually come back if you don't treat the phosphate issue.
Run some gfo, use RO water to mix, and increase your flow rate. Increasing the flow rate will get rid of it the quickest, but the three methods above mixed together will keep it gone.
You can use a turkey baster to blow it off the rocks and get it waterborne. Siphon it out as best you can. Its just one of those things that happen. Cyano-bacteria is an airborne bacteria that is one of the oldest living organisms known to man. Depending on where you live, climate, it will come and go. It looks really bad but unless it completely covers polyps, it won't kill anything.