What Are Hair Algae? (Appearance, Early Signs, Types & More)

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It is pretty common for home aquariums to develop algae. However, not everyone knows that there are different types and characteristics for each one. In this article, you will learn everything there is to know about hair algae.

Hair algae are planted-like organisms that typically thrive in areas riched with nitrate and phosphate. They are often considered a nuisance in home aquariums and are mostly known for their filamentous appearance.

As we move forward, you will learn how to identify hair alga, what typically causes it, and what its advantages are to living creatures like fish, snails, and shrimp.

What Are Hair Algae?

Hair algae are relatively common in aquariums, and they attract the same negative consequences associated with other forms of algae. This is what you should know:

1. Appearance

Professionals describe hair algae as ‘Filamentous Algae’ because it consists of long strands.[1]

It wouldn’t be an exaggeration to compare the organism to wet hair, especially when you remove it from the aquarium.[2]

This image illustrates the filamentous texture of hair algae, resembling thin strands.
The filamentous structure of hair algae is apparent under a microscope.

2. Requirements

The algae thrive in the presence of phosphates and nitrates. The higher the phosphates and nitrates, the more algae you will observe.[3]

Nitrates are typically formed from ammonia via the nitrogen cycle, which is why you can expect hair algae to form in under-maintained tanks.

Hair algae will also appear during the cycling process, but this is normal. This happens because the nitrifying bacteria haven’t fully developed yet.

Although, if it goes unchecked, the algae will turn your aquarium into a hairy mess. Even in an uncycled tank, it is still a good idea to keep an eye on the algae.

3. Forms

Aquariums are vulnerable to various types of hair algae. They typically cover phosphate and nitrate sources in the water. 

That includes rocks, plants with dying or dead leaves, leftovers, rotting fish, etc. Some types of hair algae look like a carpet. They may take on a slimy texture.

Michael Haberland, an environmental and resource management agent for Burlington and Camden counties, highlighted one version that looks and feels like cotton and another that took on a coarse texture comparable to horse hair.[4]

These versions of hair algae are not limited to aquariums. You will find them in freshwater and saltwater bodies in the wild.

A cotton-like form of hair algae, which is incredibly soft and pleasant to touch.
This form of hair algae has a more coarse texture, resembling horse hair.

4. Nutritional Value

Like other algae types, hair alga has nutritional value.

A study in Algal Research (Matthew J. Vucko, Josiah Pit, Andrew J. Cole, Rocky de Nys, Jonathan A Moorhead) found that macroalga Oedogonium has a high lipid content and plenty of amino acids.[5]

Oedogonium is the most common hairy algae genus in aquariums.[6] In ‘Freshwater Algae of North America,’ David M. John described this genus’s filaments as unbranched, attached, and without bristles.[7]

Oedogonium appears in calm freshwater sources in the wild, attaching to free-floating objects such as plants.[8]

You will observe similar behavior in the aquarium. Oedogonium alga is a viable alternative to commercial feed. Other algae types have a similar advantage.

Even though they are detrimental to aquariums in large quantities, some aquatic creatures will eat them.

Oedogonium is not the only form of hair algae at your disposal. The term ‘Hair Algae’ can refer to a multitude of algae species. 

One example is Lyngbya, which the University of Florida (Center For Aquatic And Invasive Plants) described as ‘Mat-forming Cyanobacterium‘.[9]

Cyanobacteria are fascinating because they are bacteria but also photosynthetic and aquatic.[10]

Lyngbya may appear as thick mats that cover the water’s surface. In the wild, it can encompass several acres. 

The organism can also manifest at the bottom of a water body. The long hairy appearance encourages the ‘Hair Algae’ classification.[11]

5. Removal

Hair algae are vulnerable to the same techniques that eliminate other algae types, including strict maintenance routines and manual removal.

As a rule of thumb, if you get rid of the nutrients hair alga feeds on, you will be able to control its growth.

Weekly water changes and water conditioners are the best and fastest way to fight nitrate and prevent hair algae from spreading.

Useful info: If you wish to use algae eaters to control the hair algae situation in your tank, here is an article where I listed the best species for this job.

How To Identify Hair Algae?

Hair algae are called so because they are filamentous. In other words, they have a long, stringy appearance comparable to threads.

In fact, some people call it string or thread algae. The resemblance to hair is unmistakable.

Hair algae have individual cells that link together to form longer chains, allowing the organism to grow several inches in days.

The species isn’t simply unsightly. It will entangle the aquatic creatures in your tank. It will also interfere with the functions of the filter.[12]

It is worth noting that some forms of hair algae don’t have long strands. Instead, they look like a short, fuzzy carpet or mat:

While most forms of hair algae look like thin strands, some will take on a carpet shape, as seen in this picture.

What Are The Early Signs Of Hair Algae?

Algae is easier to remove if you notice and attack it early. When hair algae first appear, they look like small patches.

Those patches can take on any color, depending on the type of hair algae you have. But green is the most common.

As such, you should look for small, green, potentially fuzzy patches. Given enough time, the strands will grow to produce long hair. 

If you still have doubts, hair algae with long strands will cover the plants, entangle your fish, and block the filter.

Here you can see a fish eating a small patch of hair algae that has just started to form on a rock.

What Are The Different Types Of Hair Algae?

Hair algae are not all the same. They will take various forms. The ones you encounter in aquariums include:

1. Green Hair Algae

You find green hair algae in fresh and saltwater environments. The fast-growing organism has strands long enough to entangle fish. 

The algae can manifest as thick bright green clumps. Even though they typically grow on plants, they will assault every corner of the aquarium if they go unchecked.

Fortunately, removing green hair algae is not particularly difficult. You can pull it out with your fingers. The organism is also vulnerable to algae eaters like shrimp. 

It is worth noting that green hair algae have various types, including spirogyra, Zygnema, and Oedogonium.

The New Hampshire Department of Environmental Services has noticed that people routinely confuse conventional green algae for green hair algae. 

But green algae doesn’t feature the long strands you find in its filamentous counterpart.[13]

Hair algae masses are slimy in texture, and the strands mimic tumbleweed in the way they move. 

If you think your hair algae is cyanobacteria, use the stick test to confirm your theory. Push the stick into the algae and lift it out of the tank. 

Cyanobacterial blooms will disperse. Hair algae will maintain its stringy appearance.

An image of typical green hair algae in a home aquarium.

2. Brown Hair Algae

Brown hair algae have a lot in common with green hair algae.

Like green hair algae, they have a slimy texture and strands that can grow up to 20cm in length. Look for matted brown clumps on the substrate.

They thrive in poorly maintained tanks with low lighting. Some people confuse brown hair algae with brown diatoms. However, diatoms look like dust. 

They don’t manifest the stringy appearance you see in filamentous algae.

Brown hair algae that have just started to grow on aquarium plants.

3. Black Hair Algae

This fast-growing alga has strands that grow to 5cm in length. It can take on a grayish color in some aquariums. The texture is coarse, at least in comparison to slimy green hair algae.

The organism is common in new tanks, attaching to plants, the substrate, filters, and every other viable surface in the water.

The algae will kill your plants if it goes unchecked. Removing the affected leaves is not enough. 

You need algae eaters like Amano shrimp that graze on the organism. Severe infestations will compel you to eliminate the affected plants.

Black hair algae are relatively long and feature a coarse texture.

4. Staghorn Algae

Aquarists classify staghorn algae as hair algae because it grows in strands. It resembles black algae, concentrating in specific areas and boasting a coarse texture

However, the strands of the grey-green or grayish organism resemble a deer’s antlers. It grows on most aquarium surfaces. 

You can use conventional algae removal tools to eliminate it, including strict cleaning regimens and routine water changes.

Algae eaters like Amano shrimp are the most efficient answer to a staghorn algae infestation.

Staghorn algae usually have grey-green shades and are shaped like antlers shape.

5. Fuzz Algae

Many people categorize fuzz algae under the ‘Green Hair Algae’ umbrella, but some aquarists dispute this idea. 

The organism grows as individual filaments on viable surfaces in the water. On the other hand, green hair algae appear as a dense coating.

Fuzz algae are not as dense as green hair algae. However, some people think that fuzz algae are an early stage of hair algae.[14]

An image of fuzz algae growing on aquarium plants and driftwood.

6. White Hair Algae

White hair algae consist of long, thin strands. People occasionally confuse them for fungus.  

Individual strands are almost impossible to see because of their color. The organism responds to common algae removal tools and methods.

An image of white hair algae growing on aquarium plants and substrate.

7. Yellow-Green Hair Algae

An article in ‘Encyclopedia of Materials: Science and Technology’ describes these algae as having sparsely branched filaments that form ‘Felt-like Mats’.[15] 

Britannica calls the organism ‘Vaucheria.’ It appears in freshwater and marine environments, common in wetlands, salt marshes, pond fringes, and the like.[16]

Yellow-green hair algae with green shades on the left and yellow on the right.

How Are Hair Algae Different From Other Types of Algae?

The most significant difference is the filamentous nature of hair algae. Otherwise, hair algae have more similarities with other algae types than differences. 

They all manifest under the same conditions, present during the cycling process and thriving in the presence of phosphates and nitrates.

You can also fight them using the same tools.

That includes algae eaters, mechanical removal, water agitation, commercial algae removers, strict maintenance routines, etc.

Pro tip: Many aquarists suffer from hair algae overgrowth. If that is your case, here is an article where I explain step-by-step how to get rid of it.

If you found this article helpful, these may also interest you:


Hair algae, also known as fuzz, thread, and filamentous algae, typically belong to the Oedogonium genus in home aquariums. 

The most prominent characteristic of this plant-like organism is the long strands it is made of, which are also the reason for its name.

Like other types of algae, you typically find hair algae in aquariums abundant with nitrate and phosphate. These nutrients usually form in overcrowded and under-maintained tanks.

However, you can also find hair algae in tanks that are in the middle of the cycling process. That is perfectly normal as the tank isn’t biologically balanced yet.


  1. https://buceplant.com/blogs/aquascaping-guides-and-tips/everything-you-ever-wanted-to-know-about-algae-in-a-fishtank
  2. https://www.aquariumcoop.com/blogs/aquarium/aquarium-algae
  3. https://theaquariumguide.com/articles/hair-algae-causes-and-how-to-get-rid-of-them
  4. https://njaes.rutgers.edu/fs1231/
  5. https://www.sciencedirect.com/science/article/abs/pii/S221192641730293X
  6. https://aquariumstoredepot.com/blogs/news/how-to-get-rid-of-hair-algae
  7. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/oedogonium
  8. https://www.britannica.com/science/Oedogonium
  9. https://plants.ifas.ufl.edu/plant-directory/lyngbya-species/
  10. https://ucmp.berkeley.edu/bacteria/cyanointro.html
  11. https://plants.ifas.ufl.edu/manage/why-manage-plants/aquatic-and-wetland-plants-in-florida/algae/
  12. https://www.thesprucepets.com/getting-rid-of-green-hair-algae-2924939
  13. https://www.des.nh.gov/sites/g/files/ehbemt341/files/documents/bb-65.pdf
  14. https://www.aquasabi.com/aquascaping-wiki_algae_fuzz-algae
  15. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/vaucheria
  16. https://www.britannica.com/science/Vaucheria