Creating an Iwagumi Layout in the Nature Aquarium

Author: Takashi Amano

The world-famous aquascape artist reveals his method for re-creating the aesthetic of a Japanese rock garden in the planted aquarium.

The Iwagumi Layout

In previous articles I have introduced many aquatic plant layouts that utilized driftwood as the main material for their composition. However, in the Nature Aquarium, rocks are the most important compositional material. An aquatic plant layout composed of rocks and short aquatic plants is called an iwagumi layout, and it is classified separately from other layouts.

Driftwood as a composition material does not project a very strong presence in a layout. This is because mosses and ferns are often attached to its surface, and colorful stem plants and other aquatic plants are used in the layout.  On the contrary, the presence of rocks as a compositional material is felt strongly in an iwagumi layout. Therefore the selection and the arrangement of  rocks and the planting method to enhance the presence of the rocks are very important for an iwagumi layout.

Emulating Natural Scenery

In the Nature Aquarium, the naturalistic appearance of the layout is enhanced through composition and planting.  It is not an exaggeration to say that the success of an  iwagumi layout depends almost entirely on the composition of rock arrangement and planting.One must work very meticulously when producing an iwagumi layout.

In an iwagumi layout, rocks are placed in an aquarium by keeping in mind an image of natural scenery with stones and rocks.  This type of scenery is often found from the upper reaches to the mid-portion of a river, a seaside, or high plains.  Since it is not possible to actually reproduce nature in an aquatic plant layout, which has a lot of limitations, we must express the image of the scenery.  It is important to observe a lot of natural scenery and commit to our memories the details regarding stones and rocks.  This information comes in handy when selecting and arranging rocks, and it is essential in creating anatural-looking iwagumi layout.

For example, many round river rocks are found scattered in the upstream of a river.  Their locations and orientation change with a natural forces, such as the flow of the river.  In other words, you can express the flow of water in a layout by recreating the placement and the tilt of the rocks.

Rocks in a seaside scene protrude above the water’s surface or sand and may appear to be separate.  However, they are often parts of a larger boulder and connected below the water surface or in the sand.  In order to express this in a layout, we must select rocks that are the same type and produce the layout by mounding substrate around the rocks so that the rocks appear connected below the surface.  As either example indicates, there is a strong connection between an iwagumi layout and natural scenery.

Creating the Iwagumi Layout

Let me explain the actual process with which I create an iwagumi layout. I am going to introduce an example of a layout in a 180-cm (72-inch) aquarium (, with the dimensions W180 x D60 x H60 cm (W72 x D24 x H24 inches).  A long aquarium with a wide aspect ratio such as this one is suitable to express the flow and breadth of water with an iwagumi layout.


As a basic rule of an aquatic plant layout, substrate is placed in the aquarium first. However, the thickness of the substrate in an iwagumi layout is different from that in a standard aquatic plant layout. In an iwagumi layout, substrate is laid somewhat thinly without sloping the ground, taking into consideration the mounding to be done later.


Once the substrate is laid, rocks are arranged next.In this layout I used the type of river rock called Hakkaiseki. When selecting rocks, it is important to choose several in varying sizes (which will depend on the size of the aquarium) from among rocks with the same texture and quality.

The largest rock is placed in the middle and smaller rocks are arranged around it in such positions and orientations that render the feeling of a constant flow of water.   In a large aquarium such as this one, it is easier to create a layout by making a group of rocks in both the left and right sides.  Once rocks are placed, substrate is mounded around the rocks and toward the rear of the left and right sides of the aquarium. Doing so gives stability to a rock arrangement and defines a composition more clearly.

The key point for mounding substrate around rocks is to use fine powdertype substrate, such as a fine-grained aquatic-plant soil, and pour it between rocks thoroughly.  This is done so you may place aquatic plants there later in order to enhance the natural feel and refine the layout.


Next, the work will advance to planting.  The substrate is dampened, since it is difficult to plant aquatic plants in a dry substrate.  You must be careful when adding water, since water can cause the mounded soil to collapse or put a crater in the substrate.  You must gently sprinkle water by hand and dampen the entire substrate.

In an iwagumi layout, the presence of rocks is enhanced by planting short aquatic plants. Although a single type of aquatic plant such as Glossostigma is sometimes used, a combination of several plants, as in this layout, produces a change in a plant arrangement.  A natural feel is produced by planting multiple plants, taking care not to hide the rocks as much as possible by using the shortest Cuba pearl grass in the foreground, the next shortest cobra grass around the rocks, and tallest hair grass behind the rocks.

It is important to plant aquatic plants meticulously between the rocks.   It is evident in this layout that cobra grass was planted carefully around the rocks at the initial planting time.  The arrangement of aquatic plants in addition to the natural appearance of the rocks enhances the natural feel of the layout.

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