Thankx, will try to make some difference in the elevation.I'm no expert, but I would bring the rocks on the right forward a few inches. Having them on the same plane (at least, they look like they are) makes it look a bit contrived, but again I'm no expert, just my personal opinion.
Thanks for the suggestion. I did moved the right rock to forward and And I couldn't slope the substrate @ the back bcoz the water outlet holes are there in the bottom.Hard to tell if you've done so already, but if not, I would slope the substrate so it's higher at the back, and like Jason said, definitely move the rocks on the right forward. If the substrate is raised at the back, it will give the tank more depth, and the rocks on the right will be lower when you move them forward down the hill too, which will also make a big difference. Don't change the positioning or angle of either group of rocks though! They look great!