Red Slime Algae (Cyanobacteria) I need some help with this!! This is a 90 gallon saltwater tank..?

I have done everything possible so far to get rid of this Cyanobacteria. I used antibiotics, red slime remover( 2 different kinds) water changes 20% I do not overfeed, reduced lighting, cleaned the sand, washed it of my rocks I am really baffled with this Cyanobacteria it has a tight grip on my tank. Please if anyone had this problem and solved it help me out o.k.!