The substrate, already mounded and rising towards the back, helps us with this task.
Basically you create an aquarium layout in three layers, especially when it comes to planting: Foreground, midground and background. This is a classic approach traditionally used in Nature Aquaria and Dutch tanks. If you only consider these layers you will not get much of a sense of depth, though. The more layers you create, the more pronounced your three-dimensional effect will be. For this reason, we try to divide our layouts into more layers in order to get more depth, as we have explained in the first basic rule (substrate mounding), however, not with the substrate alone but with all decorative elements in the tank: we try to fill the entire aquarium with plants and hardscape, to make not only each and every substrate grain on the surface visible but also every piece of rock, driftwood and every plant, to thus give the layout a powerful three-dimensional appearance. The substrate, already mounded and rising towards the back, helps us with this task. The plants and decorative materials that are placed farther back are automatically in a higher, better visible place, which makes the differentiation between the layers farther from the front quite easy.