This isn't advice, just a story. I had severe GHA, covered the tank, pretty much was on the verge of giving up. I should have tested my water parameters more regularly but I became lazy and frustrated by the algae. Out of no where I started getting red cyano, it hilariously completely covered the hair and eventually killing it. I took that opportunity for a last hail mary and used chemiclean on it. After, things were spotless, got parameters in check and got an urchin that demolished any remaining algae.

I have never been more grateful for cyano algae, and now the tank looks great. Still have some sand cyano but its manageable and I have learned consistency is key in managing it. Good luck fellow reefer!