How much flow I guess is less import than good flow everywhere. Like wright said, the red slime stuff only grows in dead or low flow areas. I had 3 koralias in my 120 tank when i had the same problem. I now have 1 wp40 instead, and it covers flow across the whole tank way better than 3 1200 koralias did. You may need a wavemaker type pump instead. Like a wp or an mp. I have never had an mp 40, but for $80 instead of $500, i think my wp 40 does a great job.
We tried chemiclean powdered version and it worked fantastically. Make sure you turn off your UV and skimmer before adding, but everything will be gone in 4 days. We used it with sps lps softies leathers etc and had no ill effects.
That red stuff is cyanobacteria. Its mostly due to high nutrients, not low flow per se. It does occur in low flow areas i agree, but just means you need to lessen nutrients. I do agree with Garbonzo though. Chemi clean works good to kill it, and then you can change your high nutrient problem while looking at a beautiful tank; it can take over and smother things like zoes if you're not careful.
Plus 2 on the Chemiclean. I have struggled with high nutrients because I am a little heavy on my bio load. I have a ton of coral, nothing was harmed, just make sure if you use it , add an air stone for the period they state. It really does work. I just wish it worked for hair algae haha. I cant seem to get rid of that.