Brown algae in saltwater aquariums that have just finished cycling happens in almost every tank. It will go away on its own in a few days or possibly a few weeks. Your snails and hermits should also help with it, when you add them.
If it really bothers you, use a turkey baster to suck it off the rocks and an algae scraper to remove it from the glass. But, it's perfectly natural and won't last long.