How to set up an Iwagumi aquarium

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This Japanese-style planted tank is known as an Iwagumi. George Farmer shows how less can be more in his latest step-by-step guide

If browsing the Internet for the latest planted aquarium and aquascaping trends you will quickly note the popularity of rock or stone-dominated layouts. These are commonly referred to as 'Iwagumi' and roughly translates as 'rock garden' in Japanese.

This style is distinct and relies rocks to provide the main impact. Usually just the one type is used In the aquarium and only a few, sometimes just one, species of plants.

This simplistic design is also matched by fish selection, where only species of display fish are generally added to complement the minimalist nature of the aquascape.  

The style is popular as it is easy to set up, requiring relatively few materials to execute effectively. However, the Iwagumi design is regarded as difficult to master, as the rocks or stones need to be positioned very carefully in relation to the aquarium’s dimensions, as well as each other. Some basic guidelines allow us to set up our rock composition effectively.

Using nature

Natural rock layouts in the wild, either on land or at sea, share common themes. Notice the strata on rock faces. Rocks in groups will follow the same strata patterns as they have been subject to natural forces for millions of years.

See how groups of rocks are formed in relation to their sizes.  Often you will see one large rock with a group of smaller rocks surrounding it. Use these observations and try to mimic these formations in your aquarium to achieve an effective and natural looking design.

Choosing rocks

Pick rocks with the size of your aquarium in mind. Taller tanks require taller rocks, shallower tanks need smaller stones. Pick the type that suits.  

I find the most interesting rocks have a lot of detailed textures and interesting shapes. Smooth boulders or large pebbles can also be used, even though these are not used very often by many aquascapers.

Colour is also important as this has a bearing on how the plants and fish will affect the whole design. For instance, you may not want to use an orange/brown-coloured rock such as petrified wood if you stock orange fish such as Harlequins, as they will not complement one another.

Collecting your own rocks is an option, but always consider how your collecting may impact on environmental sustainability.  Respect wildlife at all times.

Equipment and plants

Before choosing plants ensure your aquarium equipment is appropriate. Some species require more light and nutrients than others and, due to the nature of a carpeting plant, more light and decent circulation is often necessary. CO2 injection or liquid carbon alternatives are usually required for most carpeting species. Two T5 lamps with reflectors or equivalent are usually enough.

Common plants for Iwagumi

Unless stated otherwise, these are all carpeting plants that will enhance your Iwagumi tank:

Glossostigma elatinoides  

Hemianthus callitrichoides

Eleocharis sp.

Echinodorus tenellus

Blyxa japonica

Staurogyne sp.

Pogostemon helferi

Lilaeopsis sp.

Riccia fluitans (tied to rocks and submersed)

Vallisneria nana (background)

Eleocharis vivipari (background)

Rotala sp. (background)

Tank profile

Tank: 60 x 30 x 36cm/24 12 x 14”, 63 l/13.2 gal, OptiWhite glass, braceless, rimless

Lighting: Overtank luminaire, two 24w T5, six-hour photoperiod

Filtration: External canister with mechanical and biological media, 1,550 lph/341 gal glassware

CO2: 2kg pressurised system on solenoid, glass/ceramic diffuser, 4KH drop checker

Substrate: Full ADA system

Fertilisers: Full ADA system

Plants: Eleocharis acicularis, Hemianthus callitrichoides 'Cuba'

Fish and inverts: Trigonostigma espei, Caradina multidentata, Crystal red shrimp

Maintenance: 50% water changes every day for first 14 days, twice per week thereafter. Once a full carpet was established the Hemianthus was pruned every week to maintain a tight carpet.  Fertilisers dosed daily. Filter cleaned once a month.  Glass cleaned every week.

Comments: I usually plant heavily when initially setting up a planted tank. It was interesting that I did not experience any algae, despite the low biomass. I put this down to a restricted photoperiod, rigorous maintenance and good quality plants, substrate and fertilisers.

Starting with basics

Sanzon-Iwagumi is regarded as the most basic of Iwagumi layouts and uses just three stones or rocks. The most important is the largest stone, known as the master. This is usually positioned in accordance with the golden ratio or rule of thirds guideline, being placed one or two-thirds across the length of the tank.

The two smaller rocks are then positioned carefully to lean towards the master stone, making the design appear as natural as possible.

How to set up your Iwagumi

I am using a 60 x 30 x 36cm/ 24 x 12 x 14”, 63 l/14 gal aquarium made from OptiWhite glass that’s braceless and rimless. This style is popular as the glass has a higher clarity. When combined with overtank lighting the overall look is very effective.  

A regular aquarium is fine, as long as enough lighting is supplied.

ADA Power Sand Special is added, along with a host of other products that help to provide ideal substrate conditions from the start and throughout the tank’s life.  

These are not essential and are relatively expensive, but for those interested in following the Japanese style of aquascaping to the letter, they are considered important.

ADA Aqua Soil Amazonia is added. This is provides the plant roots with essential food, softens the water and reduces pH, making it suitable for those with hard water who want to grow more delicate plants and keep softwater fish. It leeches ammonia in the initial weeks so do not add livestock until ammonia and nitrite are undetectable. This makes it ideal for fishless cycling.

The main stone is added and I have used the golden ratio to ensure it is aesthetically balanced. This is called Mini-Landscape Rock or Seiryu Stone and has an attractive colour and texture making it popular for many Iwagumi enthusiasts. I have added a smaller stone to help support the main rock.

The remaining rocks are added, the largest first and smallest last. Ensure the rocks appear natural and balanced in relation to one another and the design as a whole. Arranging rocks can take several days and it is common for enthusiasts to leave the tank dry and constantly re-arrange the rocks until satisfied. This layout took me around 30 minutes to select.

The aquarium is very slowly filled to one-third capacity and planted up.  I have only used three pots of Hemianthus callitrichoides ‘Cuba’ and one pot of Eleocharis parvula to do so. Individual plantlets are separated and planted using tweezers. The whole process takes several hours, as there are hundreds of individual plantlets to consider.

The remaining water is slow filled using 6mm airline to prevent the substrate from clouding. I am using my tapwater which is medium hard and quite high in nitrates and phosphates.  This is not an issue as the plants can use the nutrients before algae can.  The Aqua Soil softens the water too.

All the equipment is fitted. I use a powerful external filter with glass inlet and outlet. An external inline heater keeps temperature at 25°C/77°F. A glass CO2 drop checker is fitted with a 4KH water and pH reagent solution that turns green with 30ppm CO2.  

Every day for the first 14 I change half the aquarium water to ensure no algae.

I dose the ADA liquid fertiliser and conditioner range to the letter.

Shrimp and fish are added after four weeks, by which point there is a full carpet of plants.

Check out some of our other step-by-step guides:

How to set up a Cambodia biotope aquarium

How to build a Great British aquascape

How to set up a White Cloud biotope 

This item first appeared in the Christmas 2009 issue of Practical Fishkeeping. It may not be reproduced without permission.