How to Set Up a Tank Using the Walstad Method

What is the Walstad Method?

The Walstad Method was created by Diana Walstad as a way to create a natural planted tank. Diana Walstad is a renowned ecologist, who originally published the method in her treatise called “Ecology of the Planted Aquarium”. Her treatise details how to set up a thriving aquarium environment. This aquarium environment allows the aquarium to function with minimal care needed from an aquarist.

The Walstad Method covers how to make a balanced aquarium where the fish and plants support each other without any CO2 or fertilization. The fish and plants cover each other’s needs so that the tank is almost completely self-sustaining.

Now you might think – “This is a low-tech tank!” Not it is not. The Walstad Method uses a lot of light. In addition, a properly balanced tank may not require even filtration.

This method allows you to do less water changes because the plants in the aquarium will do most of the filtering for you. With the Walstad method, you can expect to do a 25% to 50% water change every 6 months.

Ecology of the Planted Aquarium:
A Practical Manual and Scientific Treatise for the Home Aquarist – link to check the price on Amazon

Setting Up a Tank Using the Walstad Method

Tank Size Recommendations

Tank size affects how many plants and fish that you can keep in the aquarium. It also affects the maintenance needs of the tank.

If you do need to do a water change, performing water changes on a larger tank can be a little bit harder than on a smaller tank. However, considering the fact that it will not be often anyway, I do not see why you cannot go for a bigger tank.

Diana Walstad says that even a 5-gallon (20-liter) or 10-gallon (40-liter) tank is great for beginners.
Note: If you choose a smaller tank, you will need to choose smaller fish that will fit in the tank as adults.

Nonetheless, if you decide to start with a larger tank, it will give you more options. These tanks can store larger breeds of fish and more plants to balance out the tank. Avoid purchasing tanks that are taller than 18 inches, except if the tank will be receiving natural light as well.

Water Hardness Recommendations

The water should not be too soft. Soft water is actually bad for growing plants. Hard water has more nutrients (Ca, K, Mg, etc. so-called “hardwater nutrients”) that are beneficial for plant growth.

Soft water also tends to cause more pH changes than hard water. This can cause it to be harder to keep the tank parameters stable.

Temperature Recommendations

The ideal tank temperature is 75 degrees Fahrenheit (23 C). However, the temperature can safely range between 68 degrees F (20 C) and 85 degrees F (30 C).

Aquarium heaters can be used to warm up the tank. During the summer, the heater should be turned off. You can also take off the top cover which allows air to circulate better.

Light Recommendations

Here comes one of the most interesting parts. The amount of light that your tank needs depends on the size and height of your tank but in general, the author of this method recommends medium or moderate light levels for a relatively long duration daily.

Placing an aquarium by a window (with a Southern exposure), as a supplement to artificial light, in order to give the plants natural light is a great idea that Walstad also highly recommends.

Note: Of course, many people will say that more light = algae problems unless it is a high-tech tank and we use carbon dioxide (CO2) effectively. Which is still difficult and algae problems are almost inevitable. However, according to Walstad, once the fast-growing plants adjust, they should outcompete the algae. However, some tanks should receive less artificial light.

Tanks that are less than 10 inches high (25 cm) should receive less artificial light because the height makes it easier for light to reach the plants than with tanks with higher walls. Tanks that are receiving natural light in addition to artificial light should also have their artificial light limited.

Note: According to modern measurement, PAR meter should be about 30 – 40 umol at the substrate.

You should give your plants 10 to 14 hours of artificial light. You can use a light timer in order to turn the lights on and off automatically.

Light Recommendations. Siesta and CO2

Diana Walstad also advertises for short light breaks (siesta) during the day to improve the plant growth and reduce the algae.

The reason behind this trick is pretty simple.

In nature and in our aquariums, the CO2 level builds up throughout the night. In a process called “photosynthesis,” our plants use the energy in light to convert CO2 to sugar (their food) and oxygen. Multiple studies show that the plants take up almost all the CO2 by noon.

Therefore, when we leave the lights on all day long the plants have a lot of light but they do not have any CO2. As a result, plants cannot perform photosynthesis. At the same time, there is lots of light that actually favoring algae growth.

However, if we turn the lights off for 3 – 4 hours in the midday, it will allow CO2 levels to regenerate during the siesta. So, when you turn the lights on the plants will have CO2 again.

This schedule (5 – 6 hours on, 3 – 4 hours off, 5 – 6 hours on) improves the plants’ growth and helps with algae control.

You can also read my article “CO2 in a Planted Tank Guide”.

Setting up Your Substrate

According to the Walstad Method, you should have two layers of the substrate in your aquarium. The first layer should be 1 – 1.5 inches (2.5 – 4 cm) worth of unfertilized, organic soil. Generic potting soil is fine as long as it doesn’t have chemical fertilizers.

Note: Miracle Gro Organic Choice Potting Mix (MGOC) (check the price on Amazon) is often recommended by Diana Walstad herself.

When organic matter in the soil decomposes it releases a lot of CO2. These carbonates will help your plants to grow and remove harmful chemicals (ammonia and nitrates) which the plants can eat.

There should also be a second layer of substrate in the aquarium. Walstad highly recommends that you use small gravel for this layer and add no more than an inch of gravel (2.5 cm). There should be enough gravel to cover the soil in order to keep it from clouding up your tank.

Note: Sand is better suitable for a smaller shrimp tank setup because it is easier for shrimp to sift through and turn over sand grains than gravel, looking for food. Sand is acceptable as the second substrate but due to the compactness of sand, gravel is still a better option.

Compact sand (a very small fraction) should never be used because it would make it harder for the oxygen to get through.

Gravel cleaning is unnecessary in a tank created using the Walstad Method. It can actually keep nutrients in your substrate from being restored.

Substrate Preparation

Obviously, generic potting soil was not developed for aquarium usage. Therefore, you need to sieve the substrate. Organic soils often contain lots of big pieces of not-yet fully decomposed bark.
Put the soil into the tank.
Add several inches of water and stir it well.
Leave it this way for a night.
Next day, remove all floating pieces, drain the tank, and add several inches of water.
Leave it this way for a night again.
Remove the floating pieces and change the water.
If you still see lots of debris in the water and your water is still very brown you can repeat the process one more time.

If you do not sift the soil and/or do not add a layer of gravel, upon planting the soil will be distributed everywhere. It can cover plants, block the light, and cause them to melt away.

Tip: Once you start fill the tank with water, start with shallow water (1/2 of your normal water volume). By doing so, your plants will get more intense light and the CO2 exchange is a little bit faster. It will boost the growth of the plants and balance the tank faster.

Filtration and Water Circulation

The original Walstad method did not include a filter, because the plants are doing all heavy lifting. High filtrations can be even harmful to a tank filled with plants since filters remove nutrients from the water that plants need.

Unlike the common cycling method, Walstad tanks rely on the soil that naturally contains nitrifying bacteria and denitrifying bacteria. That is why the tank has to be heavily planted from the start.

However, in the latest versions of the book, she mentioned that it would be beneficial for circulation and backup (in case something happens with the plants and they start melting). For example, hang on the back filters for medium-sized tanks and tanks that are 30 inches long or longer should have a canister filter with a strong flow.

I will repeat that the most important is water circulation that transports all nutrients and CO2 equally to the plants around the tank.

The filter should allow the water to flow across the tank easier. The use of filters makes it so that you do not normally need an air stone. If you have a small tank you may not need filtration but water circulation is a must.

Note: If you have a biofilm floating on the surface, remove it. It interrupts gas exchange.

Choosing Aquatic Animals for the Tank

Walstad advises that you choose fish that remain small and don’t get too big for their tank as adults. This is because you may have to rehome these fish as adults or move them to a larger tank.

Aggressive breeds and breeds that are prone to tearing up plants should be avoided for your tank. Cichlids are extremely popular for tanks but they will destroy your plants and have a tendency to attack each other.

You should also avoid fish breeds that only eat plants if you want your plants to survive.

A moderate load of fish and plants is recommended for a tank. This creates a good balance in your tank ecosystem. Freshwater snails and shrimp are also great for a tank because they can remove excess algae. Walstad uses snails in all of her tanks to control algae growth.

Recommended Fish for a 10 to 20 Gallon (40 – 80 liter) Tanks

Dwarf Gouramis
Small Tetras
White Clouds
Zebra Danio

Recommended Fish for a 50 Gallon (200 liters) or Larger Tanks

Angelfish
Clown Loaches
Larger Gouramis
Congo Terras
Rainbows

Note: Digested fish food (waste) will also be converted into food for your plants by bacteria. It provides all plant nutrients in a safe, slow-release mode.

Choosing Plants for Your Tank

The Walstad Method emphasizes how plants can be used to help an aquarium thrive by “reducing aquarium maintenance and keeping fish healthy”. She suggests experimenting with plants and choosing a variety of plants in order to see what works for you personally.

Some common plants that she uses for her own tanks are Hornwort, Ruffled sword plant, Amazon sword plant, limnophila, Indian fern, Ludwigia Repens, etc. All of these plants grow relatively fast under the right conditions. Floating plants will also benefit the tank.

Walstad also uses Cryptocorynes, Bacopa caroliniana, and Java fern in her own tanks. These plant species take longer to become a part of the tank.

I would like to mention that in this method you do not try to keep all these plants alive at all costs. It may sound harsh but it is what it is.

After some time, when most nutrients in the substrate are used up, some plants may be outcompeted by others that can uptake nutrients more effectively including from the water column. The stem plants are usually the first to go.

This is not a high-tech tank where you are providing enough CO2, root tabs, and fertilizers, that you can keep all these plants that are not so good at getting it so you can have a wider variety of them. Let nature take its course.

How to Add Fish to an Established Tank

Fish should not be added until at least two months of tank preparation have passed. Placing fish into the tank before the water parameters are stable can kill your fish. The only exception to this rule is if you want to add aquatic animals that control algae growth such as snails.

Once the tank is established and fish are residing in the tank, you may want to add more fish. Make sure to isolate new fish for at least two weeks before adding them to the established tank. This makes it so that your original inhabitants do not catch any sort of infectious diseases from the new resident.

Quarantining new inhabitants is essential because one sick fish can pass a disease to all of the fish in your tank if you aren’t careful.

How to Treat Sick Fish

Sick fish should be quarantined away from the other fish in order to prevent the spread of disease. You should not treat fish in the original tank because some medications can mess with the natural balance of the tank, such as antibiotics.

How to Get Rid of Excessive Algae Growth

Excessive light can promote extra algae growth. If your tank is being taken over by algae, then you can try lowering the amount of light that your plants receive on a daily basis. Charcoal filters can also be used to help with excessive algae growth.

In order to determine if your charcoal filter is still working, you can add food dye to your tank. The filter should remove the food coloring by morning. If it doesn’t, you need to replace the charcoal filter.

In Conclusion

A lot of people coming into the hobby barely understand the cycling process. They are overwhelmed with lots of information about CO2 injection, fertilizers, lighting requirements, filtration, etc.

The Walstad Method is simply a more natural approach with plants, bacteria, and the balance in general. That is why there is no need to change the water. In this method, the plants filter it better than any mechanical filter.

The only real thing that you have to really focus is on water movement for oxygen exchange. Another big key is to have some fast growing plants for rapid nutrient uptake.

If you need more information about this method, you can buy the book or ask Diana Walstad here. She is moderating the forum and often answers the questions.