Usually there are 3 or 5 stones with each given a specific name. The first and largest is the Oyaishi or the main stone and is placed slightly off center. The Soeishi are the accompanying stones that are smaller and less dynamic in character. They are placed near the Oyaishi in order to highlight the larger rock. Finally, the Fukuseki are secondary stones that may be absent from some tanks. They are placed to the far left and far right and are the smallest of the three types.
After the rocks are placed as desired, aquarists like to grow a low carpeting plant that provides a natural hillside look and some slightly taller, thinner plants around the rocks for a slight contrast. Fish may or may not be present, but if they are, it is usually a large group of schooling fish to provide order rather than many different species that can appear all over the tank and taking the focus away from the scape itself.
While these tanks may seem simplistic and very natural, they are among the hardest tanks to successfully maintain and should not be attempted by the beginning aquarist.
Here are some examples of the Iwagumi style of aquascaping.