Iwagumi aquascape: stones, plants and setup

An Iwagumi is a planted aquarium whose only hardscape is a small, odd-numbered group of stones of one kind, set asymmetrically and surrounded by very few low plants, usually a single carpet. It needs nutrient soil, strong light and normally CO₂ injection, and it keeps more open space than any other major style: about 30 % in MOKIZEN's analysis of 591 published layouts.

What is an Iwagumi aquascape?

An Iwagumi is a stone-only planted layout in which a few rocks of the same kind carry the whole design and the plants act as a low, quiet setting around them. The Japanese word means rock formation or rock arrangement.

Takashi Amano (1954–2015), who founded Aqua Design Amano (ADA) in 1982, adapted it from the stone setting of Japanese gardens, above all the three-stone Sanzon arrangement. ADA places the start of his Iwagumi work in the 1980s, before the Nature Aquarium name existed. His early tanks paired Senmigawa stones with pygmy chain sword (Echinodorus tenellus) as the only plant; later ones used Hakkai and Manten stones with Glossostigma. Today most people treat Iwagumi as a branch of the Nature Aquarium style.

What are the rules of an Iwagumi?

The core rules are stones only, an odd number of them, all of one type, arranged around one dominant stone that sits off-centre. Everything else follows from keeping the stones as the subject.

• No driftwood in the strict form. Add wood and the tank becomes a general Nature Aquarium layout; a few hobby guides tolerate it on those terms.
• Use 3, 5 or 7 stones so the group can never balance into symmetry.
• Keep every stone the same type, colour and texture; do not mix stone from different sources.
• Put the main stone roughly one third to two fifths of the tank length from one side, near a golden-ratio or rule-of-thirds point, never in the middle.
• Tilt and angle the stones as if water had shaped them, ideally all radiating from one chosen point. Avoid straight lines and equal sizes.
• Limit plants to about one to three species so nothing competes with the rock.

What are the stones in an Iwagumi called?

Each stone has a job, and the first three form the classic Sanzon triad. ADA's own composition notes name three roles; hobby guides add a fourth, and the secondary stone is also written fukuseki. These are naming variants, not competing systems.

Which stones are best for an Iwagumi?

Seiryu is the most common choice: it is the stone most often used as the hero piece in the Iwagumi layouts MOKIZEN analysed. Dragon stone (Ohko), Manten, Ryuoh and similar mountain stones are also popular, and ADA has used Senmigawa, Hakkai and Manten.

• Seiryu and Ryuoh contain calcium carbonate and push up pH, GH and KH. ADA counters this with softening products and regular water changes.
• Size the main stone so the carpet will not swamp it, but not so large that it crowds the tank.
• Stand heavy stones on the bottom glass or a protective base and pile substrate around them, so they cannot shift later.
• Clean stones with water and a brush only, never soap or chemicals.

Which plants and fish suit an Iwagumi?

Choose one low carpet plant, optionally one accent, and one schooling fish species. The classic carpets are dwarf hairgrass, HC 'Cuba', Glossostigma and Monte Carlo; pygmy chain sword and Utricularia graminifolia also work. Small mosses such as Fissidens can soften stone bases, and dwarf Vallisneria or a taller Eleocharis can make a low backdrop. All of these root-feeding carpets want a nutrient aquasoil such as ADA Amazonia, Tropica Aquarium Soil or UNS Controsoil.

For fish, a single large school keeps the calm look: rummy-nose, cardinal or ember tetras, or harlequin rasboras. Amano shrimp, named after Takashi Amano who brought them into the hobby in the 1980s, and Otocinclus graze algae. Skip diggers and fish that uproot plants; they tear up a young carpet.

How do you set up an Iwagumi step by step?

Set the stones first, then the soil, then the carpet, and run the tank gently for its first weeks. Plan for strong light, pressurised CO₂ (most carpets only close up with injection) and a good canister filter giving strong, even flow across the open carpet.

1. Plan the group on paper or in a 3D planner: where the main stone goes, which way it faces, and how the triad balances.
2. Place the main stone on the base first, then the secondary and supporting stones, then any small suteishi.
3. Add aquasoil around and behind the stones, sloping it up toward the back.
4. Plant the carpet as small portions spread over the open area, or grow it emersed first with a dry start before flooding.
5. Fill slowly so neither the soil nor the plantings are disturbed.
6. Keep the photoperiod short and change water often while the new soil releases ammonia.
7. Add algae-eating shrimp early; add fish only when ammonia and nitrite both read zero.

How do you maintain an Iwagumi?

Maintenance means big water changes early, weekly routine after that, and trimming the carpet before it gets thick. Sources disagree on light at the start: Tropica suggests 6 hours for the first 2–3 weeks, then 8–10 hours, while ADA's start-up guide runs 10 hours from day one. In an open, algae-prone Iwagumi, starting at 6 hours and increasing is the safer path.

• First 4–6 weeks: frequent large water changes and a short photoperiod while plants root in.
• Weekly: change about a third of the water and clean the glass.
• Every few weeks: trim the carpet before the lower layers rot for lack of light (ADA cuts Glossostigma at about 2 cm deep), cutting tight around the stones and along the glass for a crisp edge.
• Ongoing: brush green spot and film algae off the stones and pick out beard or staghorn tufts.
• Long term: leave the stones in place and replant or change the carpet instead of rebuilding. ADA kept one stone layout going for 14 years this way.

What are common Iwagumi mistakes?

Most failed Iwagumi tanks come from weak stone hierarchy or from algae in the bright, open early weeks.

• Choosing only the prettiest stones, or stones of similar size: the group loses its hierarchy. Pick one clearly dominant stone and progressively smaller companions.
• Stones too small for the tank: the carpet swallows them. Size the main stone to the tank height and expect the carpet to rise around the bases.
• Main stone centred or stones in a row: this creates the symmetry the style avoids. Move the main stone to a golden-ratio point and vary the angles.
• Too many plant species: they clutter the minimal look. Keep to one carpet and at most one accent.
• Underestimating algae: large bare areas under strong light give algae room. Start with short light periods, keep CO₂ stable, change water often and add plenty of shrimp.

Plants and animals in this guide

• Dwarf Hairgrass (Eleocharis) (Eleocharis pusilla (sold as E. parvula / 'Mini') / E. acicularis)
• HC Cuba (Hemianthus callitrichoides) (Hemianthus callitrichoides 'Cuba' (now Micranthemum callitrichoides))
• Glossostigma (Glossostigma elatinoides)
• Monte Carlo (Micranthemum) (Micranthemum tweediei 'Monte Carlo' (WCVP: syn. of M. umbrosum))
• Utricularia graminifolia (UG) (Utricularia graminifolia)
• Fissidens Moss (Phoenix Moss) (Fissidens fontanus)
• Vallisneria (Eelgrass) (Vallisneria spiralis / V. americana (trade stock often misidentified))

See it in 3D

• Iwagumi Triad

Related guides

• Nature Aquarium style: layout rules and setup
• Balancing light, CO₂ and fertiliser in a planted tank
• Aquarium algae: identify the type and fix the cause
• How to cycle a new aquarium (nitrogen cycle)

Sources

1. ADA Review: Learn the Secrets of the Iwagumi — ADA (Aqua Design Amano)
2. ADA Review: Maintenance Technique – Iwagumi Layout — ADA (Aqua Design Amano)
3. SUIKEI Words Keyword 01: Layout composition – Iwagumi — ADA (Aqua Design Amano)
4. Nature Aquarium Starting from Zero — ADA (Aqua Design Amano)
5. Founder – Takashi Amano — ADA (Aqua Design Amano)
6. Takashi Amano — Wikipedia
7. Aquascaping — Wikipedia
8. The Iwagumi Layout: An Introduction — Aquascaping Love
9. Iwagumi Aquascape: Stone Layouts, Rules & Setup Guide — Shrimp and Snail Breeder
10. Starting a new aquarium — Tropica Aquarium Plants
11. Insights: 591 real aquascape layouts — MOKIZEN

Written from these sources; last updated 2026-09-23.

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