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One Type of Fish, One Type of Rock, the Purism of the Iwagumi Aquascaping Style.

Updated: May 9, 2022

In a previous post, I discussed biotope tanks as a style of aquascaping. Another style I am fond of is the Iwagumi style, created by famed aquarist Takashi Amano. Iwagumi translates to "rock formation", and the design concept relies on the restrictive purism of one type of fish and one type of rock. This type of aquascaping is more challenging, but liberties can be taken by the aquarist to modify the style to their liking. For example, I would add more than one type of fish, but the same size of small schooling species.


This aquascaping style relies heavily on the hardscape as a foundation on which to build. Hardscape refers to the non-living components, in this case the rock and substrate. Begin by choosing a fine grain substrate. When completed, you want everything to scale appropriately. If the substrate is large gravel, it will look unnatural against the rocks and make them appear much smaller. I would also recommend a light color if using dark rocks and a dark color substrate if using lighter rocks. Consider a fertilized substrate as well. Most of the carpeting plants used in this style are heavy root growers.

The most important part of the Iwagumi style is the selection and placement of your stones. This will be the most time consuming as the stone placement must appear as natural as possible. It is normal to live with a hardscape for days before redoing it again and again. This is part of the process and when you find the ideal arrangement, nothing is more rewarding. The two most common types of stones for Iwagumi are seiryu (pictured above) and dragon or ohko stone (pictured right). Don't hesitate to use a different type of stone, just make sure the lines flow well and use the same type of stone through out.

Function of Each Stone

Once you have chosen your style of stone, you'll need an odd number. Nature can be balanced, but is rarely even. You'll choose approximately 5-9 stones for a small tank, 11-15 for a larger one and so on. You will choose the same type of stone, but each individual stone has its own function and name. Start by choosing your main showpiece stone, called the "Oyaishi". There will only be one of these and it should be placed off-center. Next, choose your counter stone, or "Fukuishi" stone. There is also only one, it should be smaller than the main stone, and it's purpose is to visually counter the main stone. It should break up the line set by the Oyaishi stone and placed opposite, off-center. Then, choose and position one or more smaller "Soeishi" or impression stones. Their purpose is to support the visual impression of the main stone. Choose an odd number and place them around the main stone to focus the eye on it. Unlike the counter stone, the impression stones are meant to compliment, not break up the main stone's visual lines. Finally, choose your smallest design stones, the "Suteishi". Their purpose is to fill in where necessary, create that final odd number, and complete any balance in the scape.


Choosing your plants for the Iwagumi style is open to interpretation. There are several classical styles that rely on grass type and carpeting plants to keep the scale of the large landscape rocks as large as possible. Long grass types and stem plants are also used, especially when trying to bring color to the scape, such as the vivid red color of the Ludwigia sp. leaves. Don't forget to choose the right light and possibly CO2 setup to accommodate any plants you choose.


Lastly, the strictest interpretation of the Iwagumi style allows for a small number of calm, schooling fish of the same species. The idea being to recreate a tranquil landscape and the fish appear as a murmur of birds in the sky. However, there is nothing wrong with a more colorful and active interpretation and choosing a couple species of small schooling fish. Because of the openness of the design, there are few places to hide, so larger aggressive fish should be avoided as they will limit the visual potential of your schooling fish.


In the end, there are many ways to accomplish the Iwagumi style, as long as you are true to your interpretation of a tranquil landscape. If you have trouble achieving balance and no arrangement looks quite right, don't get discouraged. Try referencing some basic design elements like the rule of thirds or the golden ratio.


  • Boodleshire LLC 2022

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