If the "brown algae", brown or rusty brown colored and is like dust on the rock and sand, it is most likely diatoms, normal for new setups. It will come and go. You can siphon it off if the appearance gets to you. As for photoperiod, it isn't really important while cycling unless there are a lot of critters on your LR.
I haven't read where you have test kits. If you don't have one, this should be of highest priority. During the establishment of your nitrogen cycle you should test regularly, like every day, to see what the status is and know certain when the cycle has fully established. If you have not read this already, here are great resources:
https://forums.saltwaterfish.com/forum/thread/301033/101-tips-to-beginning-and-maintaining-a-saltwater-aquarium
and
https://forums.saltwaterfish.com/forum/thread/386044/let-s-talk-about-cycling
As stated earlier, you really need some circulation in there. I would also strongly consider some kind of background on that back glass. Painting it now would not be too much of a hassle.
What size tank is that?