Your setup is still new, its part of the cycle of starting up a marine tank. Every new tank goes through it and you have to let it run its course. If you have a good skimmer it will help pull it out of your water if you get it off the rock and floating. But, just let it run its course.
Since the tank is fresh you won't have built up nutrients in the sand bed or substrate, so that's not a issue. What did you use ?
Turbo snails will eat it, (BUT) if your tank isn't finish cycling they will die and when the diatom is gone they will more than likely die since they will battle for food. Also, don't run your lights for long periods of time. Start off 2 or 3 hrs and every other week or so add another hour till you get to the total time you would like them on everyday. Same applies when you get replacement bulbs.