I got rid of my cyano easily by vacumnng with everything off, I cut my lights back 2hs and added 2 koralia2's aimed at the worse areas no probs I left it like that and changed my water schedule to 5% every 3days and wala
I had to do a blackout when I had a bad algae bloom a few years ago same thing usd blankets because even ambiant light will help it I also used weiss algae remover gone in a few days
not sure if it's safe to use with reefs though