#cyanobacteria

Is this cyanobacteria I did two back to back treatments of cyanobacteria no improvement any suggestions?

I’m new to saltwater and bought a reef aquarium that’s a few years old. There is a horrible reddish stuff growing over everything which I’m guessing is Cyanobacteria. A worker at my LFS said it was probably due to the black sand. I really hate the look of the black sand in there anyway and am...