Create an Iwagumi Aquascape

Any aquascaper who is a fan of Nature Aquariums must have come across Takashi Amano’s Iwagumi, or ‘stone formation’ style. He developed it about 30 years ago.

When Takashi Amano was in his early 20s, he became interested in creating an aquatic layout using rocks. So he studied Suiseki, the Japanese art of stone appreciation and Bonseki, the art of creating miniature landscapes on a black lacquer tray — art-forms passed forward through an entire millenium. Neither could Amano escape the influence of the quintessential Japanese garden, in which rocks are the “bones” of the entire layout, and of which it is said that once the rock formation is placed properly, the rest of the layout will simply fall into place. These studies and his own experiments aided him in establishing the Iwagumi style.

The first rock to be placed in an Iwagumi aquascape is the primary rock or largest rock, the Oyaishi, and it is always placed off-centre, in accordance with the rule of thirds. It is also often slightly tilted in the direction of the water flow, to give it more of a natural feel, as any tall flora will also move in the same direction. After the Oyaishi, the second largest rock is placed, the Fukuishi. The Fukuishi is placed on either the left, or right side of the Oyaishi, and its role is to balance out the Oyaishi and to create tension — a characteristic seen in all Iwagumi aquascapes. The third largest rock follows the Fukuishi, the Soeishi. Again loosely following the rule of thirds, it is placed in a position that accentuates the strength of the Oyaishi. The fourth largest rock is the Suteishi, and it is placed in an area that compliments the entire rock formation, because its function is to assist in bringing all the different rocks ‘together’, to form a whole. Despite its function, the Suteishi is not  meant to stand out from the rock formation as a whole. In fact, it is frequently hidden by flora, which is why it is also known as the ‘sacrificial stone’.

Except for the Oyaishi, there can be several, or even many Fukuishi, Soeishi and Suteishi, with the numbers of the particular type increasing as the rocks get smaller. The naming of the rocks based on their sizes provides just a guideline to the Nature Aquarium aquascaper on how to produce an Iwagumi aquascape that balances itself.

Fascinatingly, many people have an innate sense for this feeling of balance, while others just do not have it, and need to follow the rules to attain it. It is always worth it to try arranging rock on your own, to discover if you do, as this will also allow you to more easily break some rules.  If you don’t — you need to follow the guidelines.


The most basic of all Iwagumi is the Sanzon Iwagumi, or ‘three-pillared rock formation’. As suggested by its name, only three rocks are used, the Oyaishi, the Fukuishi and the Soeishi. The Sanzon Iwagumi is popular among nano aquascapers because it does not take up much space. Simple and non-complicated, some of the best Iwagumi aquascapes are of the Sanzon Iwagumi style.

In an Iwagumi aquascape, the types of plants used in each aquascape is limited to a small number. Low lying carpet flora such as Hemianthus callitrichoides or Glossostigma are extensively used, while delicate flora such as Hairgrass or Vivipara are used selectively to bring into highlight certain parts of the rock formation or to ‘cushion’ the impact of the rock formation in a small aquarium. The aim of using these plants is to create and then complete the impression of a well balanced rock formation that stands on a beautiful field. It pays to keep a look-out for rock formations in nature, not only to learn from the rock, but to see how natural plants have settled in amongst and around these rocky structures.

Think about this before you begin

What do I want to see?

One of the more difficult aspects of the Iwagumi Style is achieving visual balance throughout the aquascape. Many aquascapers follow the rule of thirds, which divides the layout into three equal segments from top to bottom, and from side to side.  The focal point is placed where the different vertical and horizontal lines intersect. Of course, this does not mean measuring our tanks millimetre by millimetre. More-or-less accuracy will do. The point is that placing rocks in these areas adds strength and focus to the aquascape.

The substrate, on the other hand, sets the foundation for the visual flow experienced by the viewer. In Iwagumi aquascapes, the substrate is used to create  contours and texture to keep the eye moving and draw it into all aspects of the aquascape. A strategically planned substrate can also help create an illusion of depth, for example by sloping upward from front to back. One could also have one side of the aquarium substrate slightly higher than the other side.  Each of these methods will add more personality and depth to what initially seems like a simple design. Of course, the aim is that once the substrate is covered with groundcover plants, it should create a sensation of fluidity and movement by presenting the viewer with green rolling hills and/or valleys.

Simple and elegant, or complex and intricate?

As we already know, there are several different kinds of Iwagumi. In Sanzon Iwagumi three stones are used: one larger stone and two smaller flanking stones that lean towards the larger one, almost as if bowing to it.  This is called Sanzon Iwagumi because the three stones are likened to Buddhist triads.  Sanzon Iwagumi has a very distinctive atmosphere: it is almost regal in its majestic elegance.

But not all Iwagumi have just three stones – any number of stones can be used in an Iwagumi.  While three-stone Sanzon Iwagumi possess a striking, symbolic elegance, those with more stones have an added element of complexity and intricacy.

Whilst there is no absolute rule about the maximum number of stones, it is best to use an odd number – 3, 5, 7 or 9 stones and so on. There is a reason for this!

When we do not have that innate, intuitive sense for arranging things so that they seem to have balance, we have the tendency to arrange things in a stylised or symmetrical way — which for the natural scenes we wish to create is a  very unnatural and un-beautiful way.  It always amazes me that we are naturally drawn to patterns of randomness, and even chaos,  but that when we attempt to create something beautiful we instinctively revert to taught, stylised patterns that we actually, if we come to analyse it, find unattractive.  Using an odd number of stones prevents this tendency, and therefore helps to make the Iwagumi more attractive and natural.  It also prevents the scape from appearing to be ‘split’  and disconnected – with an even number of stones on either side.


However many stones you choose to use, they should consist of the same type of stone. This is important, because it creates continuity and provides harmony for the entire layout.

Define Your Hardscape

When you start a layout you will need more than just ‘enough’ hardscape material — meaning that you should collect extra rocks in case you change your design.  This will also give you more options when you begin to plan and build your scape. You also need different sized rocks to select from.  And you need to find rocks that have character, because the more folds, or nooks and crannies your stones have the more detailed and complex your layout will appear.

The goal is thus to find a group of rocks that share the same type and colour scheme, but are different in their individual details, patterns, shapes, and contours. Once arranged in an aquascape the rocks will then appear as a unified collection with a clear focus, while each rock still maintains its own distinct characteristics.

Thus, when selecting your stones, it is important to bear in mind their purpose within the aquascape. So let us look once more at what is required for each rock.

Oyaishi — The focal point
This is the primary  stone in the layout.  It should be the largest and most beautiful stone and must have a striking character and form.  The Oyashi or primary stone should be around 2/3 the height of the aquarium, as this ratio appeals to the human eye.

In you aquascape, the Oyashi should be tilted. Whilst Oyashi in Japanese gardens tend to stand upright, in aquascaping the stone is tilted to represent the flow of the water. (If the stone were in a river, it would naturally be tilted because of the force of the water flow.  In water, the tilt of the Oyashi gives us the most natural and beautiful effect.

Fukuishi — the secondary stone

This secondary stone should be the second largest and is placed on either the left or the right hand side of the Oyaishi or primary stone.  The Fukuishi should be similar in texture and must be the same type of stone as the Oyaishi.

 Soeishi — The tertiary stone

The tertiary stone is placed next to the Oyaishi, along with the Fukuishi.  The Soeshi plays an important role in the flow of the Iwagumi, by bolstering the strength of the Oyaishi or by accentuating its presence.

 Suteishi —  the sacrificial stone

The Suteishi is a small stone that does not stand out in its own right, and may even become hidden by plants over time.  The Suteishi is meant to add an element of subtlety, intricacy and complexity to the Iwagumi. The Suteishi can be omitted from the aquascape if you are creating a three-stone Sanzon Iwagumi.

Helping or Throwaway stones

The basic stones of Iwugami are used in any number of combinations, and in larger, more intricate scapes are often combined with ‘Helping’ or ‘Throwaway’ stones — smaller nondescript rocks that need not fit any of our formal definitions.

As in Japanese gardens, two and three stone groups are the norm and can be combined to create larger (but not principal) focal points. If you have read about Japanese gardens, you will know that there are five stone groups that are usually the main focus of a Japanese garden, often in the ‘guardian stone’ position. This is a very powerful grouping and needs careful balancing, should you wish to attempt it.

Here are some ideas to inspire you:

Placing of the first stone


Placing of the second stone


Top view of the completed Layout


Front view of the completed Layout


Laying out a traditional Iwagumi

At the end of this article, I will add a step-by-step image guide taken from an Amano lecture, in which you can see how he goes about creating an aquascape.

  •  For a traditional Iwagumi, lay an even layer of substrate across the floor of the aquarium.  More substrate will be added after the stones have been placed.If you work with large rocks, you may want to place your stones on the bare bottom, so that they later appear embedded in the substrate.
  • Note: If you want a more complex and varied Iwagumi then the substrate can be laid more thickly at the back or back corners of the aquarium.
  • Next, place the Oyaishi.  It is important to place the Oyaishi first.  Place it in accordance with the Rule of Thirds – so the stone should be about 2/3 the height of the aquarium and placed at a point that is either 1/3rd or 2/3rd  the front width of the aquarium away from the left or right wall — and back from the front wall around 2/3rd of the aquarium’s front to back depth.
  •  Then arrange the remaining rocks in descending order of size, placing the largest first and the smallest last: Fukuseki first, then Soeishi and finally Suteishi last.  Pay attention to the balance of the angles of the rocks to help you place the stones.
  • When you have a layout that you are happy with (and this may take a couple of attempts!), it is best to leave the aquarium for a day or two so you can consider the layout for a while.
  •  Finish the layout by using a cup, or container to carefully pour more substrate over it to mound the substrate naturally.  Let the substrate flow naturally between the stones.  Finish with a layer of Aqua Soil Powder for a fine effect. 

 Planting the Iwagumi

Aquatic plants soften the visual impact of the stones, so they are used to create a harmonious balance within the aquascape.   Since the Iwagumi style should give you a feeling of tranquility and simplicity, a  limited number of plant species are used.

An aquascape will usually consist of a single foreground plant like Eleocharis acicularis (Dwarf hairgrass), Glossostigma elatinoides, and Hemianthus callitrichoides to name a few commonly used species.

 Low growing plants are used to accentuate the details of a rock arrangement and are thus planted between the rocks, or next to them. Their placement is critical if you are to create a natural effect. You must make sure that your low growing plants will not obscure the inherent structure of your Iwagumi.  Suggested plants include Hemianthus callitrichoides ‘Cuba’, Eleocharis parvula (hair grass), Eleocharis acicularis – Exceptional Value Range and Glossostigma elatinoides to name but a few.

The background should also only consist of one plant species,  or at most two,  and can vary based upon the look and feel you want to obtain. Higher growing plants such as Eleocharis vivipara can be used in the background of an Iwagumi to add depth and intricacy to the scape if desired. But remember that the rocks are the focal point in an Iwagumi aquascape. So always use plants in such a way that they that will not overpower the rock formation.

Harmony with Fauna

When selecting fish, you want to emphasise simplicity, harmony, and unity between the fauna and the aquascape. You are looking for a meditative effect, not excitement. Too many fish species cause discord and chaotic random movement among the fish, which distracts from the aquascape.

Instead use just a single species of schooling (not shoaling) fish to add fluid movement and contentment to the aquascape. The most common used species are Cardinal tetras, Rummy nose tetras, or Harlequin rasboras.  It is important to use “schooling” fish and not “shoaling” fish. It is a matter of harmony. Shoaling fish form loose groupings, in which each individual remains free to do what it wants, often splitting off from the group. In contrast schooling fish will not only swim closely together, they will form a very tight formation and will swim in a very synchronized manner. A school of fish can perform very complicated manoeuvres such as changing direction or turning as a whole. This behaviour is perfect for an Iwagumi Aquascape, as it helps to maintain a more tranquil environment.

Shrimp like the Caridina japonica (Amano Shrimp) are most often used in the planted aquarium to serve as an excellent clean up crew, without distracting the aquascape. Their small size and clear coloration helps them blend well with the plants. Other shrimp varieties can be a distraction if they are too colourful or too abundant.

It is not as Easy as it Looks

Due to their simplistic look, it is a common misconception that Iwagumi style aquascapes are easy to maintain. In fact, it is a more difficult style,  mainly because the style involves only two or three plant species, all of which require special attention. The plants mentioned previously are all heavy root feeders, so dosing the water column should be done in moderation.  It is much more important to have a nutrient rich substrate to help these specific plants grow strong and healthy.  Many hobbyists overlook the importance of a nutrient rich substrate, and without it they may run into plant health issues later, as the aquascape develops.

It is possible that your aquascape may fall victim to algae in the early stages, before the tank is properly balanced. Be observant, and at the first sign of algae, immediately do a water change and add floating plants to your tank, and possibly also some stem plants in mesh pots just resting on the floor at the back. While this may temporarily change the feel of your aquascape, these helper plants are great at mopping up the over-supply of nutrients in the water – and they are infinitely better than grabbing at the chemicals! Add enough to do the job, but do not shade the carpeting plants too much. They still need light to grow. The latest scientific information lets us know that a lighting break of about one hour over midday works wonders as an algae fighting tool. Apparently the plants do not mind this break, but the algae cannot survive it.  So add a timer to your lighting set-up!

Before we proceed to the step-by-step demonstration, I want to show you some inspirational images, each of which is a totally different and individual take on Iwagumi.

A close-up if the Scape above. Note the texture of the rocks. This adds beauty and intricacy to an otherwise very simple but artful arrangement!

Continued on the next page: Step by step demonstration as Amano sets up a tank.