It's probably just diatoms and a perfectly normal part of the process in a new tank. Diatoms scrub off very, very easily. You can use a magnet cleaner on the glass, and a toothbrush and a turkey baster to scrub and blow off the rocks. Clean the glass as often as you want, but the rocks and sand can wait until water change day. It's best to do your scrubbing a little while before a water change so it can get picked up by mechanical filtration or settle for vaccing out.