I tried all methods of fighting Red Slime without additives, and it just kept coming back. The red Slime killed off parts of my gorgonians and my closed brain as I was trying to kick it naturally.
I used " Red Slime Remover" and It was gone completely in 24hrs. No ill effects whatsoever. I know several others who have used it with success also.
I even tried "Erase" and ran into all sorts of problems. Killed my colerpa in my refugium and my bubble coral took a beating also!
My opinion is, "get rid of it now, before it kills stuff. Then deal with the cause, so it doesn't come back".
If your phosphates are a problem, use Rowaphos. IMO the best stuff out there!. Does not leach when exausted!