Essential Iwagumi Principle
In an Iwagumi aquascape you should always use an odd number of rocks of various sizes, and they should consist of the same type of stone. This will add continuity and provide harmony for the layout.
One of the more difficult aspects of the Iwagumi Style is achieving visual balance through the aquascape. Many aquascapers follow the “golden triangle rule” which divides the layout into three equal segments from top to bottom, and from side to side. The focal point is where the different vertical and horizontal lines intersect. Placing rocks and groups of plants in theses areas will adds strength and focus to the Iwagumi aquascape.
The substrate sets the foundation for visual flow for the viewer. In Iwagumi aquascapes, the substrate should have contours and texture to keep the eye moving and drawn into all aspects of the aquascape. A strategically placed substrate will also help create an allusion of depth. Sloping upward from front to back is a great way to achieve this depth. You can also have one side or your aquarium substrate slightly higher than the other side. Each method will add more personality and depth to what seems like a simple design.
The substrate once covered with groundcover plants will create a sensation of fluidity and movement with green rolling hills and valleys.
Define Your Hardscape
When you start a layout you should always have more than enough hardscape material than you need. This gives you more options when your initially planning your design. You don’t want to be limited by a small selection of rocks. I recommend having at least seven different sized rocks to select from. Find rocks that have character, the more nooks and crannies your stones have the more detailed and complex your layout will appear.
Some of the more popular stones to use are Seiryu-seki stone, Maten stone, or Shou stone. These rocks are excellent rocks to use for your hardscape, but your not limited to these types. The goal is to find group of rocks that share the same color scheme, but are different in their details, color patterns, shapes, and contours.
When put arranged in an aquascape the rocks will appear as a unified collection while still maintaining their own distinct characteristics. The arrangement of the hardscape should have a clear focus and dictate the viewers’ perspective.
Select the Right Aquatic Plants
Iwagumi style should give you a feeling of tranquility and simplicity; therefore 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.
The background should also only consist of one plant species and can vary based upon the look and feel you want to obtain. The rocks are the focal point in an Iwagumi aquascape. So always use plants that will not over power the rock formation.
Harmony with Fauna
When selecting fish you want to emphasis simplicity, harmony, and unity between the fauna and the aquascape. Too many fish species can cause discord and chaotic random movement among the fish, which distracts from the aquascape.
Instead use a single species of schooling 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. This helps to maintain a more tranquil environment.
Shrimp like the Caridina japonica (Amano Shrimp) are most often use in the planted aquarium and 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 colorful or too abundant.
Not as Easy as it Looks
It is a common misconception that Iwagumi style aquascapes are easy to maintain due to its simplistic look. It is in fact a more difficult style mainly because the style involves only two plant species which require special attention. The plants mentioned previously are heavy root feeders, so dosing the water column should be done in moderation. It is 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 may run into plant health issues later as the aquascape develops.