The Iwagumi Style

Iwagumi (Japanese for "rock formation") is one of the most challenging yet rewarding aquascaping styles. Defined by its bold stone structures and elegant simplicity, it draws inspiration from Japanese rock gardens.

History & Philosophy

The Iwagumi style was developed by Takashi Amano in the 1980s as part of the Nature Aquarium movement. However, its roots go back centuries to traditional Japanese gardening principles.

The philosophy centers on creating a sense of flow and balance using only stones and low-growing plants. It is a test of the aquascaper's ability to create a harmonious layout with minimal materials.

Key Design Principles

1. The Sanzon Iwagumi (Three-Stone Layout)

The most classic formation consists of three main stones:

• Oyaishi (Main Stone): The largest and most impressive stone. It is the focal point and dictates the flow of the entire scape. It is usually tilted slightly against the flow of water.
• Fukuishi (Secondary Stone): The second largest stone. It supports the Oyaishi and provides balance. It is placed on the opposite side or adjacent to the main stone.
• Soeishi (Tertiary Stone): A smaller stone placed near the Oyaishi to emphasize its strength.

2. Odd Numbers

Always use an odd number of stones (3, 5, 7, etc.) to avoid symmetry, which feels artificial.

3. Simplicity

The planting is typically limited to one or two species. This restraint highlights the texture and form of the stones.

Hardscape Materials

• Stones: Seiryu, Ryuoh, or Hakkai stones are popular choices for their dramatic textures and colors.
• Substrate: Fine, uniform soil or sand is used to create a clean base.

Typical Flora and Fauna

Fauna

Fish should be small and schooling to maintain the scale of the landscape.

• Cardinal Tetras
• Rummy Nose Tetras
• Harlequin Rasboras
• Otocinclus Catfish (for algae control)

Flora

Carpeting plants are the stars of an Iwagumi.

• Hemianthus callitrichoides 'Cuba'
• Eleocharis parvula (Dwarf Hairgrass)
• Glossostigma elatinoides
• Micranthemum 'Monte Carlo'

Challenges

The Iwagumi style is notorious for being difficult to balance. With limited plant mass, algae can be a significant issue in the early stages. Careful monitoring of lighting and CO2 is essential.