A Little Introduction to the Walstad Planted Aquarium Method

Also referred to as the "dirted" style of planted tanks, the Walstad Method is a low-tech method to keeping a thriving aquarium using organic processes of the ecosystem within.

A bit of aquarium history: Back in the late 90s freshwater aquatic plant enthusiasts were focused on new “high tech” planted tanks. Aquarists and manufacturers were adapting high-intensity metal halide reef lights, dosers and controllers for use on planted aquariums. A typical high tech planted aquarium used metal halide pendant lights suspended over an open-top tank. The bright lighting coupled with carbon dioxide (CO2) injection allowed aquarists to keep plants that were normally very difficult to keep alive. Some aquariums even used under gravel substrate heaters to help circulate water and nutrients through a bed of specialty substrate. These aquariums were all quite large because they had to be deep enough to handle the intensity of the metal halides. If you wanted to keep live plants, you had to go big and purchase all the gear needed to complete the system. Then along came Diana Walstad, who completely changed the game with her introduction of a

Who is Diana Walstad?

Diana began fishkeeping at an early age.  Later in life she focused on planted aquariums. Always having trouble growing plants in the past, Diana remembered how well aquatic plants grew in a dairy farm’s sludgy, outdoor stock tank. If they could grow there, why not in an aquarium? She set up an aquarium with a layer of soil covered by aquarium gravel. Other aquarists had been growing individual plants in pots with soil. Why not in an aquarium? She placed the aquarium near a sunny window and filled it with plants. With no help from fertilizers or CO2 injection, the plants grew and thrived. From there Dianna began experimenting and figuring out the science behind this “organic” method of keeping a planted aquarium. She eventually wrote Ecology of the Planted Aquarium to describe her techniques, which later became known as the Walstad Method of keeping giving readers their first introduction to a low-tech planted aquarium.

What is the Walstad Method?

The Walstad Method borrows from nature and European ways of keeping planted aquariums. In fact, before electricity, freshwater aquariums were kept using many of the same concepts in the Walstad method. Diana used modern science to explain why these techniques all fit together for a successful planted aquarium.  Here is an introduction to some of the key “Walstad Factors.”

  • Use of an organic soil layer under the gravel
  • No extra fertilizers
  • Bacterial processes provide CO2; no CO2 injection system needed
  • Minimal maintenance and water changes
  • Minimal to no filtration (maybe just a pump)
  • Adequate light levels
  • Different plant species will react differently

How does the Walstad Method work?

Much of the science behind the method is based on using natural processes to supply the plants with what they need to grow. In nature many aquatic plants grow in nutrient-rich soil. The plant roots extract the nutrients from the soil. A thin layer of soil on the base of the aquarium provides similar nutrients for the aquarium plants. Small gravel is added on top to keep the soil in place. Fish food and tap water also supply essential trace elements and minerals. Ammonia from fish waste also feed the plants. The soil is home to a variety of microbes that break down organic matter and release nutrients to the roots. This process also slowly releases carbon dioxide. Natural CO2 production makes carbon dioxide injection unnecessary.

Allelopathy and Natural Algae Control

Some aquarists have trouble with algae when trying to grow plants. The Walstad method recommends using a lot of plants and few water changes. This comes from the science of allelopathy. With aquatic plants, allelopathy is a process where a plant produces one or more chemicals that influence other plants in the same aquarium. Many plants release substances that inhibit algae growth. Densely-planted aquariums typically have less algae problems because of allelopathy (and less nutrients in the water). The Walstad method takes full advantage of allelopathy by minimizing water changes that dilute the chemicals. Use of activated carbon may remove some of these algae-suppressing compounds so it is not normally used.

Does the Walstad method work for all aquatic plants?

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No. Experience demonstrates that not all plants do well with this method. Here’s why. Certain types of aquatic plants, specifically the “stem” and “carpet” types demand bright light and CO2 injection. By design the Walstad method uses less powerful lighting. This is so the plant growth is kept to a medium rate without the need for extra CO2.  The idea is to have adequate plant growth with minimal reliance on “aquarium tech” like fertilizer and CO2 injection. The truth is, some plants will thrive while others die back. This could be caused by one species inhibiting the other (allelopathy) or simply the wrong environment. That’s part of the magic of the Walstad method. Every aquarium is different and balances itself out over time.

What about fish?

Like everything else in this planted aquarium philosophy, balance is key to success. You can keep just about any plant-friendly fish in a planted aquarium. Their colors will be beautiful and many will breed. The main thing is not to over-stock or over-feed. The idea is to have a healthy small population of fish that fits into the ecology of the aquarium.

Shrimp love planted aquariums

Dwarf shrimp are more popular than ever. There are many colorful varieties that will thrive in a Walstad-style aquarium. You’ll get the beauty of a planted aquarium along with the interesting and colorful antics of dwarf shrimp.

Does the Walstad method work in nano aquariums?

Yes. Today there a wide variety of small rimless aquariums to choose from, like AquaMaxx, Dennerle, and Lifegard Aquatics, which are suitable for this method. Some aquarists have even chosen to set up multiple small tanks, each with different plants, fish or shrimp. With their small size, the tanks can be placed near a sunny window without obstructing your outside view all the while providing natural light for the plants.


As an introduction, know that the Walstad method incorporates many natural processes to create a balanced, low-tech planted aquarium, so results may vary. If your goal is to have an easy to careful planted aquarium this philosophy is right for you. You’ll find this style of aquarium requires little care, looks beautiful and is a great way to explore the wonders of a planted tank. 

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