Why The Heck Do I Still Have Red Slime Algea?!

[rastaangel]

Bacislly I have been constantly battling red slime algea in my tank and nothing seems to get rid of it completely other then sucking it out when I do water changes but it always pops back up...
I just tested my water and have 5.0 nitrates and 0 phosphates (trates are usually 0, but I did a LPS feed 2 days ago).
I cant figure out why I still have cynoa popping up... I run a BRS dual reactor w/ high capasity GFO, carbon, and another reactor full of seachem purigen....
Anyone got a solution or a suggestion?