I'm with Jin on this one. Export it.
Cyanobacter is one of the worlds first and oldest life forms. You will never kill it all - it's in every tank even when you do not see it.
When it starts to accumulate such as what you're seeing, there's something feeding it - excessive nutrients etc., and low flow in the spots where it settles.
Siphon it out, but also look at the causes. Change up the flow so it doesn't settle there but watch it might settle someplace else.
If chemical means are used as a last resort, I prefer Ultralife Red Slime Remover - it works similarly to Chemiclean but it's less volatile and more forgiving. I've used it with clams and inverts with no ill effects.
Jenn