I love the way it looks, but some of those flat pieces look like they want to fall, they are tilted, I'd try to level them just for aesthetics.
My other thought is caves look cool, but they take up space for corals. If you stack it more stepped like you'll be able to place corals there instead of a space that really doesn't do much.
It's up to you though, it can always be changed down the road, but I know when I ran out of room, the caves we're the first to get changed. I hate my areas that are not illuminated, they are like dead space you know what I mean?
C