If it wasn't for the small rock on top of the right structure, both sides would be very similar.
That being said, when corals begin to cover the rocks, the structures will look more different.
Here are a few tips:
- The top rocks are placed horizontally. Try to place them tilted up or down.
- Create passages inside each structure. Most fish will love those small spaces and caves and it also makes watching them going around their businesses more interesting.
- Most of your rocks have similar size. I would break at least one of them in 2. It will make achieving the 1st tip much easier.
- Try to make the rocks fit into each other as seamlessly as you can.
- You also try rotating the structures in a way to prevent the tank from having a straight line of depth. Diagonal lines and bays will create more interest.