How to Grow Algae: 10 Steps (with Pictures)

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How to Grow Algae: 10 Steps (with Pictures)
How to Grow Algae: 10 Steps (with Pictures)

Algae are aquatic plants that use nutrients from water and sunlight to grow. Many different species can be grown for any number of purposes: from food to a source of biodiesel for trucks. One of the advantages of growing algae is that the process is quick and easy.


Part 1 of 3: Creating a Culture Medium

Grow Algae Step 1

Step 1. Choose a container

The chosen container must be transparent so that the algae receive sunlight. A glass or plastic option is ideal.

Are you growing seaweed for the school science fair? Use something the size of a plastic water bottle or even bigger, like a small aquarium

Grow Algae Step 2

Step 2. Fill it with water

The culture medium consists mainly of sterile water. Pour the water into the transparent bowl.

  • To grow microalgae, use sterile salt water.
  • Do you want to grow spirulina? Use clean, fresh water. You can use water from any source, including a tap or a spring, as long as it is filtered with activated carbon or a ceramic filter.
  • If you don't want the algae to be contaminated by bacteria, boil the water first to lessen the risk.
Grow Algae Step 3

Step 3. Add nutrients to water

In nature, algae coexist with other aquatic species. These creatures keep the underwater ecosystem balanced and provide many of the nutrients needed by the algae, such as nitrates, phosphates and silicates. In the water container, there are no such nutrients and micronutrients as metals and vitamins without their addition. You can buy a nutrient solution or get some water from a fish tank.

  • Aquarium water can introduce other contaminants into the culture medium.
  • You can even mix nutrient solutions. Conway medium is a suitable option for propagating algae.
  • Comparing the effects of different nutrient solutions can be one way to study algae for a science fair project.
Grow Algae Step 4

Step 4. Find a place with lots of sunlight

Before adding algae, you need to know if there is a suitable environment for them. Look for a window sill or a safe place outside that gets a lot of sun. In this way, sunlight provides the energy necessary for the algae to reproduce and develop in the culture medium. Didn't find a place with these conditions? Use grow lamps.

  • Research the species of alga to be cultivated to find out which bulb is best for you. A common light for growing plants may not be very effective for certain species of algae. In some cases, it is required to emit mainly red and orange light.
  • Each species of alga requires a different amount of light. Furthermore, temperatures above 35ºC can be fatal for your species.

Part 2 of 3: Adding an algae sample to water

Grow Algae Step 5

Step 1. Choose a type of seaweed

Recent research suggests that there are more than 70,000 species of algae, and possibly many others as yet uncatalogued. We use them for various purposes. Some algae are used to produce biofuels for electrical components. Others, like spirulina, are used as food. There are algae grown in the laboratory for scientific experiments and classes. The purpose you intend to give should define which species to cultivate.

  • For example, spirulina is a good option for those who want to grow algae to complement their diet.
  • Spirogra is sometimes used in scientific projects.
Grow Algae Step 6

Step 2. Collect an algae sample

For a basic experiment, you can use any type of algae, grow it and observe it. Is the intention to observe algae growth in general? Just collect a sample from either ponds or other natural sources. As there are many species of algae in nature, you need to be more careful about where to take the sample if you want to research a specific species. In this case, it is even better to buy the chosen option at an algae shop for aquaculture or online.

  • Many people are interested in cultivating spirulina. As it is ingested, only buy a sample from a renowned brand.
  • Is algae farming just for a science class experiment? It's okay to collect a sample from a lake or fountain.
Grow Algae Step 7

Step 3. Place the sample in the culture medium

After choosing the seaweed, place the sample in the water in the container. Secure an adequate amount of light and wait for it to grow.

  • Sometimes weeks and weeks go by before you can see the algae inside the container, which is because many species (called microalgae) cannot be seen with the naked eye. They need to reproduce and generate a large population for them to become noticeable.
  • If the species is a macroalgae, such as kelp, it is possible to see it.

Part 3 of 3: Watching algae

Grow Algae Step 8

Step 1. Observe any color changes in the culture medium

As the algae grows, they become more and more compact inside the container. The denser the population, the more opaque the solution becomes. Most algae crops are green, but there are other species of different colors.

  • For example, the algae of the phylum Rhodophyta are red.
  • Keep a record of all the changes they undergo.
Grow Algae Step 9

Step 2. Add nutrients as needed

In the case of a short-term experiment, you may only have to add nutrients at the beginning. However, for a long-term crop, add them to each new batch of algae. You also need to provide more nutrients as the population grows. If you are unsure how much to use, consult an algae specialist.

If the population becomes too dense, it may be necessary to divide it into a new container. Otherwise, a bowl is enough for cultivation

Grow Algae Step 10

Step 3. Look at them with a microscope

Want to better understand your culture? Look at algae under a magnifying glass. Place a drop of the culture on a microscope slide to see much more than you can detect with the naked eye. In addition to algae, sometimes you can even find protozoa or other forms of life.

If it's a school or work science experiment, observation can be part of the project


  • If the algae overgrows, you can use them to feed some aquarium pets.
  • How about making a diary or blog with photographic records of the evolution of algae? This is an interesting idea to complement a school project.
  • Controlling the pH and salinity of the water also optimizes algae cultivation. Optimal levels depend on the species you are growing.


  • Do not give seaweed to children as they can ingest it.
  • Do not eat algae unless the species is edible, such as spirulina.

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