OK, I really like this. I am wondering if there is a way to lower the rock on the right side. Maybe it should be the one of the left, I don't know. It's not the fact they are almost the same height, though that's part of it. It's that one is really "beefy" and the other is skinny/pointy. Also, the texture in the rock goes in a different direction. It may be easier to move the bigger rock but I would do the smaller. It may be as simple as tilting it a direction of just lowering it down.
That said, I would be perfectly happy if that was my tank. Great job.