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Duckweed & Azolla Ponds


Growing duckweed and/or Azolla in a small homestead setting can be an excellent idea for several reasons, and it brings some cool benefits too. Let me break it down for you:

Reasons to Grow Duckweed:

1. Livestock Feed: Duckweed is a tiny aquatic plant that grows super fast. You can use it to feed your chickens, ducks, or other farm animals. It’s packed with nutrients like protein and vitamins, which keeps your animals healthy and happy.

2. Cost Savings: By growing duckweed as a homegrown animal feed, you can save money on buying commercial feed. It’s like having your little farm-to-table operation, but for animals!

3. Wastewater Treatment: Duckweed is awesome at cleaning up water. You can use it to treat wastewater from fish tanks or aquaponics systems. It acts like a natural filter, taking out harmful stuff and keeping the water clean for the fish.

4. Garden Fertilizer: After you’ve used duckweed for wastewater treatment, you can scoop it up and use it as a natural fertilizer for your garden. It’s like a bonus gift from nature!

Benefits of Growing Duckweed:

Photo by Blue Moon: https://www.pexels.com/photo/river-surface-covered-in-duckweed-8899693/

1. Easy Peasy: Duckweed is super easy to grow. You don’t need fancy equipment or a huge space. Just a little pond or container with some water, sunlight, and voilà!

2. Super Fast Growth: Duckweed grows like crazy! It multiplies quickly, so you’ll always have a fresh supply of feed for your animals.

3. Eco-Friendly: Growing duckweed is eco-friendly because it helps reduce waste. It cleans up water and turns it into valuable food for your animals.

4. Healthy Animals: With all the nutrients in duckweed, your animals will be healthier, which means more eggs from chickens and happier animals overall.

5. Fun Science Project: Growing duckweed can be a fun science experiment. You’ll get to observe how fast it grows and learn about how plants can help clean up water.

6. Farm-to-Table Feels: It’s like having your little farm buffet for your animals. You’ll know exactly what goes into their food and where it comes from.

So, if you’re interested in taking care of animals, saving some money, and doing something great for the environment, growing duckweed on your small homestead is the way to go. It’s a simple, rewarding, and green adventure right in your backyard!

Growing Duckweed

Here’s a more detailed step-by-step guide on how to grow duckweed in ponds:

1. Selecting the Pond:

  • Choose a pond that receives plenty of sunlight throughout the day. Duckweed thrives in well-lit environments.
  • Ensure the pond has minimal water movement, as excessive currents can sweep away the duckweed.
  • See how to build a pond later in this article

2. Testing Water Quality:

  • Before introducing duckweed, test the water quality of the pond. Measure pH levels, temperature, and nutrient levels (nitrogen, phosphorus, etc.).
  • Duckweed thrives in nutrient-rich water, so make sure the pond has a moderate to high nutrient content.

3. Preparing the Pond:

  • Clear the pond of any debris, excessive algae, or invasive plants that could hinder duckweed growth.
  • If necessary, add organic matter or small amounts of fertilizer to enhance nutrient levels in the water.

4. Obtaining Duckweed:

  • Obtain duckweed starter culture from a reputable source. You can get duckweed from other pond owners, local nurseries or local Farmers Whatsapp groups.
  • A small amount of duckweed is enough to start with, as it multiplies rapidly.

5. Introducing Duckweed:

  • Gently place the duckweed on the surface of the pond. You can disperse it evenly across the water to encourage uniform growth.
  • Avoid overcrowding the pond with duckweed to prevent competition for nutrients and space.

6. Monitoring Growth:

  • Regularly monitor the duckweed growth and population. Duckweed can reproduce quickly, doubling its biomass every few days.
  • If the duckweed covers more than half of the pond’s surface, consider harvesting some to control its growth.

7. Harvesting Duckweed:

  • Harvest duckweed regularly to prevent it from covering the entire pond, which could lead to oxygen depletion and harm fish or other aquatic life.
  • Use a fine mesh net or scoop to collect the duckweed from the water’s surface.
  • Use the harvested duckweed as a nutritious supplement for livestock feed or as a green manure in the garden.

8. Nutrient Recycling:

  • Duckweed is rich in protein and nutrients. Instead of discarding the harvested duckweed, use it to supplement the diets of livestock or poultry, which can lead to cost savings on commercial feed.

9. Managing Duckweed Growth:

  • If the duckweed population becomes excessive, consider composting it or using it as mulch in the garden.
  • Composting duckweed helps recycle nutrients and prevent it from becoming an invasive nuisance.

10. Controlling Invasive Species:

  • Regularly inspect the pond for invasive plant species that might outcompete duckweed or disrupt the pond’s ecosystem.
  • Promptly remove any invasive plants to maintain a healthy duckweed population.

11. Water Quality Maintenance:

  • Regularly monitor and maintain good water quality in the pond. Ensure proper aeration and circulation to support fish and other aquatic life.
  • Manage excess nutrients to prevent eutrophication, which can lead to algal blooms and negatively impact the pond’s ecosystem.

By following these steps, you can successfully grow duckweed in ponds, harnessing its rapid growth and nutrient-rich properties to benefit livestock, fish, and the overall health of the pond ecosystem. The above just showed the steps briefly. More detail is below:

Ideal growing conditions

Duckweed Growth Factors:

  • Optimum water temperature for growth: 20°C to 28°C
  • Suitable pH range for growth: 6.5 to 7.5
  • Minimum water depth in duckweed ponds: 30-50 cm
  • Maximum allowable wind speed: 0.3 m/s
  • Preferred water movement: Slow moving water with slight agitation
  • Ideal growing temperature: Above 70°C (for faster yields)
  • Preferred duckweed species for production: Lemna minor

Tips for Successful Duckweed Growth:

  • Grow in multiple locations to find the best micro-climate for production and reduce the risk of failure.
  • Avoid growing duckweed in the same pond as fish, as they may eat the crop.
  • Provide enough surface area for duckweed to spread and grow.
  • Use nutrient-rich water, such as tilapia waste water or compost teas, for optimal growth.
  • Ensure adequate oxygen supply through aeration to prevent water from going anaerobic.
  • In aquariums, duckweed can limit the growth of algae due to its floating nature.

Duckweed Characteristics:

  • Duckweed reproduces asexually and does not rely on pollination for reproduction.
  • It can grow several inches thick in high production conditions.
  • Duckweed has the smallest flower in the world but is rarely observed during growth.

Duckweed as Animal Feed:

  • Duckweed can be grown and fed to dairy animals, small ruminants, poultry, and ducks.
  • A small pond of 120 cm x 240 cm x 2.54 cm (4’x8’x1″) can yield about 0.5 kg of green fodder protein daily at no cost.
  • Cows and buffaloes enjoy eating duckweed, once they get used to it.

Building the pond


To build a duckweed pond using a UV-proof plastic liner, follow these steps:

Step 1: Site Selection Choose a location for your duckweed pond that receives ample sunlight throughout the day. Avoid areas with excessive shade, as duckweed requires sunlight for optimal growth. Ensure that the ground is level to prevent uneven water distribution.

Step 2: Calculate Pond Size Determine the size of the duckweed pond based on your available space and intended usage. A suggested size for a small duckweed pond could be 2 meters wide by 4 meters long and 30 centimeters deep (2m x 4m x 0.3m).

Step 3: Procure Materials Purchase a UV-proof plastic liner suitable for pond construction. The liner should be durable and resistant to degradation from sunlight exposure. Additionally, gather materials for securing the liner, such as rocks or sandbags.

Step 4: Prepare the Ground Clear the chosen area of any debris, rocks, or sharp objects that could damage the plastic liner. Level the ground to ensure uniform water depth.

Step 5: Lay the Plastic Liner Unroll the UV-proof plastic liner over the prepared area. Ensure that the liner extends beyond the pond’s dimensions to allow for secure anchoring.

Step 6: Shape the Pond Carefully shape the liner to conform to the desired pond size. Smooth out wrinkles and creases to create an even surface.

Step 7: Secure the Liner To prevent the liner from shifting, secure the edges using rocks, sandbags, or other heavy objects. This will also help to anchor the liner during water filling.

Step 8: Fill the Pond Fill the pond with water from a clean and reliable source. Allow the water to sit for a day to dechlorinate if tap water is used.

Step 9: Add Duckweed Once the pond is filled, introduce duckweed to the water. You can use a small amount of duckweed from an existing pond or obtain duckweed from a reputable source.

Step 10: Monitor and Maintain Regularly monitor the pond’s water level, temperature, and duckweed growth. Ensure that the water remains at the recommended depth of 30 centimeters. Add water as needed to compensate for evaporation or seepage.

Important Tips:

  • Always use a UV-proof plastic liner to protect the pond from sunlight and extend its lifespan.
  • Choose a location with good sunlight exposure for optimal duckweed growth.
  • The suggested pond size is 2 meters wide by 4 meters long and 30 centimeters deep (2m x 4m x 0.3m), but you can adjust the size based on your needs and available space.

By following these steps, you can create a functional and efficient duckweed pond using a UV-proof plastic liner, providing you with a sustainable and nutrient-rich feed source for your animals or other beneficial uses.

To learn much more about growing duckweed and building large duckweed ponds visit the excellent work by the Owlcation team here.

Here’s another nice explanation on how to build duckweed ponds.

Methods to maintain water temperature

Consider that, in an African village or farm located in semi-arid or desert regions with no power supply, it can be challenging to maintain a stable water temperature in the ideal range for duckweed growth. However, there are some simple and practical methods that can help mitigate extreme temperature swings and create a more favorable environment for duckweed cultivation:

1. Shade the Pond: Construct a simple shade structure using locally available materials like bamboo, palm fronds, or cloth. The shade will help protect the pond from direct sunlight during the hottest parts of the day, reducing the water temperature.

2. Select Optimal Location: Choose a location for the pond that maximizes shade during the hottest hours of the day. Consider positioning the pond under large trees or close to buildings to benefit from their shadow.

3. Increase Pond Depth: A deeper pond will experience slower temperature fluctuations than a shallow one. Increase the pond’s depth to about 30-50 centimeters (or more if possible) to provide some temperature stability.

4. Insulate with Earth: If the pond is shallow, create a thermal buffer by covering the sides and bottom with a layer of earth. This will help regulate temperature changes, keeping the water cooler during the day and warmer during the night.

5. Evaporation Reduction: Reduce evaporation by covering part of the pond’s surface with floating materials like plant debris or empty containers. This will help retain heat in the water and also conserve water.

6. Collect and Store Rainwater: During rainy seasons, collect rainwater in other containers or a nearby reservoir. This water will likely be cooler and can be used to refresh the duckweed pond, helping to regulate temperature.

7. Pond Depth Variation: If possible, create a portion of the pond with varying depths. The deeper area will have more temperature stability, providing the duckweed with a refuge from extreme heat.

8. Insulate at Night: Cover the pond at night with blankets or cloth to trap some of the daytime heat and prevent excessive cooling during the colder nights.

9. Windbreaks: Plant windbreaks, such as fast-growing shrubs or trees, around the pond area to minimize the cooling effect of strong winds on the water surface.

10. Use Local Knowledge: Consult with local experts or experienced farmers who are familiar with the microclimate of the area. They may offer insights into the best practices for maintaining water temperature in such conditions.

By combining these methods, you can create a more stable environment for duckweed growth in the semi-arid or desert regions, enhancing the productivity of your duckweed pond and providing valuable feed for your livestock or other beneficial uses in the community.

More things to consider

Adding water flow and oxygen

Plants need to breathe, so you need to put oxygen into your water. This can be done with a solar panel and an air bubbler, but you can also build your own wind turbine to move the water gently. This will add oxygen and provide some water flow which your duckweed loves.

We can build a very simple tool that helps to add oxygen into the water. We build a vertical wind turbine.

This is what a simple and cheap home-made wind turbine can look like
You could add the wind turbine to your pond like this.

Here’s a good website showing how to build a vertical wind turbine

Harvesting Duckweed

Take out ¼ of the duckweed each day. It will grow back in a day. So if your pond is 1m x 2m, then you can take out 1m x 50cm.of duckweed every day.

You could also take out half the duckweed every second day. Just keep the whole water area covered so that algae do not get light and start growing.

What can go wrong?

Common issues that duckweed farmers may face include:

1. Mosquito Breeding:

  • Issue: Stagnant water in duckweed ponds can become a breeding ground for mosquitoes, leading to increased mosquito populations.
  • Remedy: Introduce mosquito-eating fish, like guppies, into the pond to control mosquito larvae. Ensure there is minimal water movement to discourage mosquito breeding.

2. Algae Overgrowth:

  • Issue: Excessive algae growth can compete with duckweed for nutrients and sunlight, reducing duckweed productivity.
  • Remedy: Maintain a healthy and dense cover of duckweed on the pond’s surface to suppress algae growth. Use natural nutrient sources (e.g., animal waste) to promote robust duckweed growth.

3. Water Temperature Extremes:

  • Issue: Extremely high or low water temperatures can adversely affect duckweed growth and lead to crop failure.
  • Remedy: Provide shade for the duckweed pond to reduce water temperature during hot days. For colder climates, consider using greenhouse structures to maintain warmer temperatures.

4. Duckweed Matting and Self-Mulching:

  • Issue: Duckweed can pile up at the edges of the pond or form thick mats, which may lead to self-mulching and reduced growth.
  • Remedy: Minimize water movement to prevent duckweed from accumulating at the edges. Trim or harvest excess duckweed regularly to avoid self-mulching.

5. Nutrient Imbalance:

  • Issue: Insufficient or excessive nutrients in the water can affect duckweed growth and lead to sub-optimal yields.
  • Remedy: Regularly monitor nutrient levels and pH in the water. Adjust nutrient inputs (e.g., animal waste) accordingly to maintain a balanced nutrient environment for duckweed.

6. Pond Water Evaporation:

  • Issue: Arid climates may experience significant water evaporation, leading to decreased water levels and increased salinity.
  • Remedy: Install a simple shade structure over the duckweed pond to reduce evaporation. Collect and use rainwater to replenish pond water.

7. Disease and Pests:

  • Issue: Duckweed can be susceptible to certain diseases or pests that may impact its health and growth.
  • Remedy: Practice good pond hygiene, and avoid introducing contaminated water or plants. Isolate and remove affected duckweed if any disease or pest issues arise.

8. Unwanted Plant Species:

  • Issue: Invasive or unwanted plant species may compete with duckweed for resources and space.
  • Remedy: Regularly inspect the pond and manually remove any unwanted plants. Avoid introducing plant material from unknown sources. Also use multiple ponds in multiple places to reduce risk.

9. Poor Water Quality:

  • Issue: Poor water quality due to pollution or toxins can harm duckweed growth.
  • Remedy: Ensure that the water source is clean and free from pollutants. Regularly test water quality and take corrective measures if necessary.

By being attentive to these common issues and implementing appropriate remedies, duckweed farmers can enhance the productivity and health of their duckweed ponds, leading to a successful and sustainable crop for various applications, including animal feed and environmental benefits.

Azolla vs Duckweed

Azolla and duckweed are two different aquatic plants, each with its own unique characteristics and benefits. Here are the key differences between them and the reasons why one might choose to grow one or both of them in an arid or semi-desert environment:

1. Growth Habit:

  • Azolla: Azolla is a free-floating aquatic fern. It forms small clusters of leaves that float on the water surface, interconnected by tiny roots that dangle into the water.
  • Duckweed: Duckweed consists of tiny, free-floating aquatic plants with simple oval or round leaves. It floats individually on the water surface and does not have visible roots.

2. Nitrogen Fixation:

  • Azolla: One of the main advantages of Azolla is its ability to fix atmospheric nitrogen through a symbiotic relationship with cyanobacteria called Anabaena azollae. This means Azolla can convert nitrogen from the air into a form usable by plants, making it a valuable natural fertilizer.
  • Duckweed: While duckweed does not have nitrogen-fixing abilities, it can still be nutrient-rich if grown in water with sufficient nutrients or provided with supplemental nutrients.

3. Nutrient Requirements:

  • Azolla: Azolla prefers nutrient-rich water and thrives in environments with higher levels of nitrogen and phosphorus.
  • Duckweed: Duckweed can grow in a wider range of nutrient conditions and can still be productive even in less nutrient-rich water.

4. Growth Season:

  • Azolla: Azolla generally grows better in cooler seasons and colder climates.
  • Duckweed: Duckweed prefers warmer temperatures and grows better in summer or in warmer regions.

5. Water Depth:

  • Azolla: Azolla prefers shallow water, and its growth can be inhibited in deeper ponds.
  • Duckweed: Duckweed can grow in both shallow and deeper water, providing more flexibility in pond depth.

Reasons to Grow Azolla in Arid or Semi-Desert Environments:

  • Azolla can provide a natural source of nitrogen to enrich the soil, which is beneficial for other crops grown in the area.
  • It can be used as green manure, improving soil fertility and enhancing agricultural productivity.
  • Azolla can create a cooling effect on water bodies, reducing evaporation and conserving water in arid environments.
  • The high-protein content of Azolla makes it a valuable feed supplement for livestock.

Reasons to Grow Duckweed in Arid or Semi-Desert Environments:

  • Duckweed is highly versatile and can grow in a wide range of nutrient conditions, making it suitable for varying water qualities.
  • It can provide a fast-growing and nutritious feed source for fish, poultry, and livestock, helping to alleviate the scarcity of feed in arid regions.
  • Duckweed’s ability to multiply rapidly and cover water surfaces can reduce evaporation and conserve water in ponds.

Growing Both Azolla and Duckweed:

  • If the water conditions and climate allow, growing both Azolla and duckweed can offer a complementary and diverse feed source for animals and improve overall water and soil health.
  • Having a combination of nitrogen-fixing Azolla and high-protein duckweed can provide a more balanced and sustainable nutrient cycle in the ecosystem.

Ultimately, the decision to grow Azolla, duckweed, or both in an arid or semi-desert environment would depend on the specific conditions, water availability, and the intended use of these aquatic plants for agricultural or livestock purposes.


Learn more about growing Duckweed or Azolla with these videos:

Here is a very detailed video – about 40min long – a proper class on duckweed.

Youtube Video on producing Duckweed and Maggot

How to grow Duckweed.
Detailed video also showing how to add organic fertilizer to the pond

Additional sources:

Online classes on how to grow duckweed.

Detailed article on how to grow duckweed.

Duckweed growing tips and tricks.

About feeding duckweed to animals.

For scientific work on Duckweed as an animal feed:

A detailed book by the FAO:

Duckweed as a fish food.

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