Fish tank help and suggestions

[Deash7]

Hello i will be posting a picture of my fish tank, i decided to pick this up and start this as a hobby, but this is the first time iv ever done a saltwater tank. so im learning as i go you could say.

I have some brown-orangish algae on my tank glass and also in the sand, i was kind of wondering if anyone might know what that is, and how to tank care of it. i have had this tank for about a month and a half.

Landscape wise i dont have much as you can see and i would like some suggestions, but cheaper ones because i have a limited income as of right now.

I will be adding a fuzzy dwarf lionfish to my tank that has 2 clarkis in there now, the reason i wanted my salt water tank is for a lionfish, im also looking at getting some invertabrates because i have none and id love to have an arrow crab in there, but i would like suggestions. another question i have is do you think the lionfish would eat the arrow crab?

Dont be to harsh on me please im doing this tria because i enjoy fish and especially learning about saltwater as most of it is forgeign to me.

but thanks for help ahead of time thanks.

[Deash7]

picture of my tank

[leebca]

If you follow along with this post, you'll find that the brown 'algae' is normal and explained to some extent:
Setting Up a FOWLR Aquarium

You can search for 'brown algae' and find many posts. It is really diatoms that require organics and dissolve silica. Doesn't go away totally, but should get to a not-so-noticeable state when the tank matures. In the meantime, use snails that eat it, to help control it.