Algae as Fertilizer: Does It Help Plants Grow?

 by Dr. Steve Hruby
Reviewed by Dr. Steve Hruby

I am a chiropractor, father, husband, coach, entrepreneur, and motivational speaker. Feeling good about yourself is a choice: My mission is to transform lives through optimized health and overall well-being.

  Fact Checked
 by Rhealyn Tropia, RMT
Reviewed by Rhealyn Tropia, RMT

I’ve been called a Data Ninja, The Fact Checker, and a Human Search Engine. I’m an indie content curator who does research daily, and quizzes myself on the important issues of the day.

algae as fertilizer

Algae is a rich source of protein and important nourishment, owing to which it has also been a part of the human diet for decades. In recent years, the application of algae hasn’t been limited to its consumption for various health benefits. Due to their high functionality, algae have become a popular sustainable source of biomass for fuel, fertilizers, feed, food coloring, and other co-products.

Using algae as a bio-fertilizer isn’t a new concept, these microorganisms have been employed for years by many farmers to increase the soil’s nutritional value. Algae as fertilizer is an environment-friendly and reusable option that can help with high productivity. In the current times, when sustainability has become vital, using algae as a bio-fertilizer instead of chemical-based fertilizer makes a lot of sense. 

In the article, we’re going to answer the questions like: is algae good for plants and does algae help plants grow…

Why Algae Is Effective As Fertilizer

We all know that soil fertility is the basis of the organic farming system. A fertile soil with high nutritional value is what plants and crops require to grow and flourish. Algae is a great source of nutrients and organic matter that is beneficial for the soil and plants. Therefore, using algae as a fertilizer can improve the growth and yield of plants.

Let’s understand in detail how algae works as an effective fertilizer for plants:

1 – Nutrients

Algae release micro and macronutrients when it decomposes or breaks down in the soil. These nutrients help fuel the growth and yield of plants and crops. In comparison to synthetic fertilizers, algae are also a sustainable and renewable option for the required nutrients.

2 – Potassium

Algae works as a great organic and sustainable alternative to synthetic Potassium Fertilizers. When composted, algae bind well with the soil and also raise its water-retention capability. Along with this, algae even enhance soil aeration, which leads to more effective absorption of nutrients.

Brown and Red Algae

Marine algae like red algae and brown algae are rich sources of potassium, which is essential for the growth of plants. Potassium aids root growth and increases the drought-resistance capability of plants. On the other hand, a lack of potassium in the soil can contribute to a drop in crop yield and growth. Therefore, potassium is an essential micromineral that plays an important role in plant growth.

This is the reason why these algae have been used as farmland fertilizers or by farmers whose land is near the sea.

Green-blue Algae

Blue-green algae is a rich source of potassium and also has anti-fungal properties. The presence of blue-green algae in the soil effectively reduces soil loss in the rainy season. This enhances the physical and chemical characteristics of the soil.

Blue-green algae are also capable of restoring soil nutrients through the release of bioactive substances and exopolysaccharides. BGA also aids in the reclamation of sodic soils by decreasing the amount of exchangeable sodium (which causes changes in the pH of the soil).

This is the reason why blue-green algae have also been widely used for rice plants as a biofertilizer. This alga not only restores soil nutrients but also boosts the nitrogen content of the paddy fields. This is how blue-green algae can even be used as a viable alternative to chemical seed treatments. 

3 – Rapid Decomposition

Algae facilitate the process of decomposition when mixed into compost. This happens because the release of nitrogen by algae aids the breakdown of other components in the compost piles.


4 – Lessens the Loss of Soil During Rain

Algae reduce soil loss during the rainy season by acting as soil humus. It enhances the soil’s water retention capacity by binding with the soil. In addition to this, dried algae can also increase soil aeration. Well-aerated and oxidized soil results in easy absorption of nutrients by the roots and, in turn, their vigorous growth.

5 – Garden Maintenance That Is Secure and Ethical

Algae is an environment-friendly, renewable, and economical fertilizer for the soil. Due to their organic nature, algae make for a secure, ethical, and safe alternative to chemical or synthetic fertilizers. If you prefer using all-natural supplements for your houseplants or kitchen garden, then using algae as a fertilizer is the best option.

Algae being rich in proteins, vitamins, and nutrients not only helps plants grow faster but also prevents the environment from being negatively impacted. They are sustainable and all-natural, as well as a reusable source of fertilization.

Making Algae Fertilizer: A Guide

Step 1

Let the algae grow into the water body, like a lake or pond. It will start off as a thin layer but eventually form clumps. You can harvest algae from the lake or water body once the clumps are formed.

You can collect algae from the pond by using a pool skimmer or algae net.

Note that you have to extract the algae before the blooming stage, as their nutrient value decreases as they reach the blooming stage.

Step 2

In case you have harvested the algae from saltwater then this step is important to be followed. On the other hand, if you collected the algae from freshwater, then you can skip this step.

You must thoroughly rinse the algae you collected from salt water with fresh water. Algae collected from saltwater have a high salt content; therefore, it’s required to rinse them. This will remove all the excess salt possible from the algae, which can be used further.

Step 3

The harvested algae must now be dried. For this, you can place the algae on cardboard and break up the clumps. Breaking the clumps into small pieces will speed up the drying process of the algae. Next, let the algae dry completely in the sunlight.

algae in the pond

When the algae are completely dry, to the point where they crumble, they are ready to be used. Crush the algae with your hands into a powdered or soil-like consistency.

Step 4

Now, the algae crumble is ready to be used in compost or potting soil. Add and mix the crumbled algae thoroughly into your desired medium. Now your soil is ready to be used with the algae fertilizer to help you achieve higher yields and vigorous growth.

Some important points to note:

  1. It’s important to keep in mind that you harvest the algae before the blooming state. Harvesting it before the blooming state will keep its nutrient value intact.
  2. Make sure to let the algae dry completely so that there is no algae growth on top of the soil. In case the algae aren’t dried well, they might start growing on top of the soil, hindering the growth of the plant. They might especially prevent the growth of young plants that are just starting to sprout.
  3. It’s important to make certain that the algae are dead before using it as soil fertilizer
  4. Also, using a lot of algae will allow its growth above the soil which will hinder your plants’ growth. So refrain from making use of more algae than required.
  5. For avoiding the algae to grow on top of your medium, you should ensure that the top of your soil is dry between the waterings.
  6. If left unattended algae bloom can also attract bugs such as gnats witch which can harm the plants or crops. These bugs will eat the roots of the plants and increase the chances of plant diseases.

Related: What factors help algae thrive

Benefits Of Using Algae As Fertilizer

If you’re wondering what is algae good for, here’s a quick rundown of the advantages of using algae as a plant fertilizer:

  • Eco-friendly and Sustainable- Algae are a sustainable and renewable source of nutrition for the soil thus they are safer and environment-friendly. Using algae comes under good agricultural practice as it reduces the risk of soil and water pollution.
  • Rich in nutrients- Algae is a rich source of macronutrients and micronutrients required by plants and crops. Therefore they effectively help the plants or crops thrive.
  • Reduces soil loss caused due to rain- Dried algae helps the soil retain water by binding to it as soil humus. Algae also increase soil aeration. Thus, algae are a good all-natural option to reduce soil loss caused due to rain and aid the roots of plants to absorb nutrients effectively.
  • Speed up the decomposition of compost- Algae facilitates the process of decomposition by releasing chemicals and nutrients into the soil. The nitrogen released by the algae also helps in the breakdown of other materials in the soil heaps.
  • Rich source of potassium (red and brown algae)- Red and grown algae are a rich source of potassium. Potassium is required by plants as it enhances the growth of the roots and even improves their drought-resistant capability.

Frequently Asked Questions About Algae As A Fertilizer

Here are some generally asked questions relating to algae being used as a biofertilizer:

body of water turned into green

Are Seaweeds Effective Fertilizers?

Yes, seaweed fertilizers are effective on almost all types of plants because they are rich in minerals, protein, and iodine. Seaweed fertilizers contain essential vitamins and complex carbs, which provide vital nutrients to plants that are important for their growth and development. Besides their amazing nutritional content, seaweed fertilizers also promote bacterial activity in the soil.

Other benefits of seaweed fertilizers are: improving nutrient intake by the roots, improving resistance to pests and diseases, and reducing abiotic plant stress. Seaweed fertilizers even improve the root nutrient intake of plants or crops.

Seaweeds such as kelp, laminaria, or bladderwrack can be added to soil or compost heaps as an effective biofertilizer.

Can Pond Scum Be Used in the Garden?

Yes, pond scum can be used in the garden. Pond scum or algae are living organisms that are rich sources of nutrients and nitrogen. This means they can not only break down quickly in the compost pile but also increase their nutritional value. Pond scum as fertilizer for your garden plants would add essential nutrients like phosphorus and potassium to the compost.

For using pond scum as garden fertilizer, all you have to do is collect it from the pond using a rake or swimming pool skimmer. Then let the scum dry completely. If you collect algae from saltwater, remember to rinse them before drying. Next, crush the dried scum and add it to the compost pile. Besides this, you can also use other natural sources rich in nitrogen, such as coffee grounds, fresh grass clippings, or vegetable scraps.

Which Algae is Commonly Used as Fertilizer?

Blue-green algae are the most commonly used type of algae as a fertilizer. Blue-green algae or cyanobacteria are extensively used as a biofertilizer due to their nitrogen-fixing capability. Blue-green algae are a natural part of the freshwater ecosystem and obtain energy from photosynthesis. They are capable of converting nitrogen from the environment into ammonia. They have specialized cells called heterocysts for this purpose.

Besides this, Chlorella Vulgaris and seaweed species such as Gracilaria Verrucosa and sargassum sp. are extensively studied algae species as biofertilizers. Red and brown algae are also widely used by farmers because of their high content of potassium.

Do Plants Like Algae Water?

Although algae are considered a good biofertilizer to be added to the soil, using algae water for plants isn’t a good idea. Using algae water for irrigation may affect the appearance or quality of your plants. This is because algae-affected water may be deprived of nutrients required by the plants. This is similar to algae growing on the soil, pots, or plug trays, which absorb nutrients that are meant for your plant.

light green substance in water

Besides, algae is also an indicator organism, which means that in the presence of algae, conditions are more favorable for other pathogens (plant diseases) to thrive.

Therefore, using algae as a soil fertilizer is a good idea if you’re looking to enhance the growth of your plant all-naturally. For this can check out above guild for making algae fertilizer above in this article. And if you ask, is algae water good for plants? Then the answer is no, in fact, it makes more sense to avoid algae-affected water for plants.

Can Algae Destroy Plants?

Although algae can’t directly destroy your potted plants, they can actually deprive them of nutrients and hinder their growth. The reason is that algae may take up the essential nutrients and food available for your plant. This will reduce the levels of nutrients available for plants, making them suffer to thrive. They can also slow down gas exchange in and out of the medium, which can in turn slow down root growth.

If you ask how to get rid of algae in potted plants? Then, it can be done simply by changing the growing conditions. Making the conditions less favorable or suitable for the algae can help you get rid of them. Algae often grow where there is an abundance of nutrients and moisture. Thus, by cutting their food supply and reducing moisture, you can dispose of them.

You can also add some bleach if you’re trying to get rid of them from your aquatic tank or even a water tank. Bleach kills algae as well as prevents their growth. 


Overall, algae as fertilizer are a nutrient-rich natural source to replenish the soil and help plants grow and thrive. More importantly, they are sustainable, organic, and don’t even harm the environment. Chemical fertilizers, on the other hand, are effective at increasing soil fertility but degrade it over time.

Algae, as a natural source of various essential macro- and micronutrients required by plants, aids in faster growth and higher yield. Using a natural fertilizer like algae also helps reduce soil and water pollution. Over and above this, algae are an economical alternative to conventional synthetic fertilizers. Also, we can’t deny the fact that reducing the agricultural population is the need of the hour in the path of environmental sustainability.

Besides being an amazing biofertilizer, algae have other important applications such as a biofuel or jet fuel, spirulina as fish food, food coloring, food dyes, food thickeners etc.

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