Diatoms on dry rock? Cyclying

[DAWREEFER]

This is my first saltwater tank and my dry rock is getting a orangish hue. Doing some of my own research I think these are diatoms, I wanted a second opinion and what to know my best course of action. I have just a turbo snail and a emerald crab in here so far. There is a window that lets natural light into the tank, which I could easily close. I have not added a light to this tank yet. Should I be concerned and try to treat this or should I just wait for it to run it’s course? The picture was taken about 3 days ago.

 

[Garf]

Normal progression. I would be more worried if you didn’t get it. If it gets stringy, that’s a different matter :)