So you think It would be better to have nothing on the sand?If you take those corals off the sand, it will immediately look much better. This will also allow you to move the left structure a bit to the front, creating a more noticeable separation between the 2 structures and increasing the sense of depth.
It will also look more interesting as soon as you place some corals on top of the left structure to make it higher when compared to the right structure.