I too had a massive bloom, I had all this nice pretty bright white Substrate, then came home from work and it was a little brown. Came home the next day, and it was BROWN! Everything was brown... Even the brown stuff had brown stuff on it
So, I did what any person new the wonderful hobby of marine fish keeping would do, I shouted profanity while freaking out about my tank. I then calmed down a bit upon reading somewhere(I think here) that it was normal, but I was still dubious, I mean, DANG, There was a buttload( <- I think thats a Metric measurement) of this brown stuff everywhere. about 4 or 5 days ago, it started to die off and continues to do so as my counts get closer to zero. I picked up a couple (ok, 6) small crabs and 5 turbo snails so far for it and they are gradually getting things further under control.