Orange algae or spreading Coral

[ronronearr]

I have this Orange film that is growing on my sand. I also get film algae on my walls that I brush or scrape off, is this the film algae just on the sand, or is it the circled coral spreading?

if it helps, the Orange disappears at night when the lights go off then becomes brighter and more Orange in the mornings as it gets more light

 

[Saltyreef]

Looks like a diatom bloom. Common for a new tank while your biodiversity competes with eachother. The diatoms are winning. Likely due to food source in sand.