LAYOUT vol.004

English version of this article originally published in
Tropical Fish Hobbyist Magazine.

In Nature Aquarium, the layout composed of only rocks as its composition material is called an Iwagumi layout. “Iwagumi” is also a term used for the rock arrangement in traditional Japanese gardens. It is intended to create the scenery of rocks like those found in nature. However, in the case of Iwagumi in Japanese gardens, only its form has been passed down from generation to generation over the long course of history, and at the present time it appears to be highly stylized and quite removed from nature. Iwagumi in Nature Aquarium is different in the sense that natural looking Iwagumi is created based on the accumulated memory of the information obtained by observing many natural sceneries with rocks. Although the scenery created in an Iwagumi layout does not actually exist, it still moves its viewers as a proverbial expression of nature.

Getting Started

Although the composition of an Iwagumi layout is simple, a natural looking Iwagumi cannot be produced without a serious consideration of the balance of the sizes of rocks, placement, angle, and orientation of the rocks. As for the basic Iwagumi method, three rocks of different sizes - large, medium, and small - are arranged as a group of Iwagumi as shown in the photograph. Depending on the size of an aquarium, another group of Iwagumi with different size rocks may be added as shown in the layout introduced in this article. An important factor to keep in mind at this point is the flow of water. By keeping the orientation of the rocks uniform, it becomes possible to express massive water current like a river in an Iwagumi layout. On the contrary, if the orientations of the rocks are all different, the flow of water is difficult to perceive and the layout appears unnatural. This is difficult to express in words. However, you may be able to understand intuitively by carefully observing real rocks in a river.

To create an Iwagumi layout, you must first gather some rocks. There are many different types of rocks in various shapes, colors, and textures - such as river rocks, mountain rocks, and lava rocks. Another thing you need to keep in mind here is to use the same type of rocks and match the color and texture of rocks in an Iwagumi layout. Since the same type of rocks sometimes comes in slightly different colors and textures, you need to collect a number of very similar rocks in various sizes. You should collect more rocks than you need and decide which ones to use by actually arranging them in the aquarium.

Arranging the Rocks

As a technique to make Iwagumi appear natural, I sometimes arrange striated rocks by matching the direction of the lines on their surfaces. Mounding some substrate material around the arranged rocks can make them appear as if they are connected underground. With this technique you can arrange multiple rocks together to appear as if they are one large rock. I recommend that you try this technique when you cannot find a rock in the size that you had in mind. Mounding substrate material around rocks is an essential technique in an Iwagumi layout. Mounding ties rocks and substrate together naturally and creates the sense of unity. The trick for mounding substrate material is to lay the substrate material thinner than usual and then pour the powder-type Aqua Soil between the rocks. A proper size plastic container makes this work easy. The power type Aqua Soil has fine grains which produce a smooth surface. It is also suited for growing the type of aquatic plants that spread by sending out runners over the surface of the substrate such as hair grass and Glossostigma. You can also arrange a number of small rocks around an Iwagumi to enhance the natural feel. Although growing aquatic plants will eventually hide these small rocks, the layout appears more natural with just a few of them showing or by creating an area where aquatic plants do not grow.

The Plants

Next I am going to explain how to plant aquatic plants in an Iwagumi layout. The classic planting pattern is to plant one type of short aquatic plant in order to accentuate the presence of the rocks. Glossostigma, riccia, hair grass, and Echinodorus tenellus are the commonly used plants that are well suited for this. Combining these plants can vary the layout. In the layout introduced here, the planting of Blyxa and Eleocharis vivipara give perspective and a natural feel to the layout. Eleocharis vivipara belongs to a family of hair grass and grows narrow linear leaves. It goes together very well with Iwagumi and produces a layout with a tranquil refreshing impression when planted in the background. Planting hair grass in front of rocks and Eleocharis vivipara in the background produces perspective in the layout in contrast to the Iwagumi protruding slightly forward. The empty space in the center gives the depth to the layout. Blyxa is planted between rocks. Blyxa, which grows short tape-shaped leaves densely, has a soft subdued green color and goes well with the mountain rocks (Mantenseki) used in this layout. Planting this aquatic plant between rocks or behind them imparts the natural feeling to the layout as if summer grass is growing around rocks in the field.

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