Yep, it looks like diatoms. They show up in newer tanks, though can show up whenever.
They feed off of silicates and will die off once those are used up.
You can syphon off what's on the sand, wipe it off glass, and a turkey baster works well for the rocks.
This explains a little more about diatoms and other algae.
http://www.reefcleaners.org/index.ph...d=54&Itemid=60