You are currently viewing 12 Types of Algae You may Encounter in your Aquarium Tank

12 Types of Algae You may Encounter in your Aquarium Tank

Fish may seem like the perfect pet or hobby but fish aquariums are high maintenance due to several reasons; one of them being algae growth. To begin with, you must know what algae are. Algae are simple living organisms, without a DNA. They can perform photosynthesis like all green plants but lack other features like stem, leaves, and roots, etc. Algae growth is inevitable as an aquarium owner.

That disgusting film residue on your tank glass, that never seems to budge despite all your efforts, might just be your fault. Like all organisms, when provided with optimum conditions like water, light, and nutrients algae grows like wildfire. Algae bloom is almost like weed growth in a garden. The key to control is maintaining the right amount of nutrients and light since water is already a mandatory factor in all tanks. Algae growth is a natural process but an excess of anything is bad, similarly excess of algae growth may be hazardous to the plants and fish.

Whether you are hereafter noticing the unsightly substance coating your fish tank or just an amateur wanting to know the pros and cons before splurging on an aquarium, the main step is recognizing the types of algae that may exist in your aquarium. Then come the steps to get rid of it and prevent it. The seven major divisions of algae are:

  • Euglenophyta
  • Chrysophyta (golden-brown algae and diatoms)
  • Pyrrophyta (fire algae)
  • Chlorophyta (green algae)
  • Rhodophyta (red algae)
  • Phaeophyta (brown algae)
  • Xanthophyta (yellow-green algae)

All species of algae are subdivided into these seven categories. Below is the list of the most common types of aquarium algae, that you will probably have to deal with.

Here is a list of algae that could potentially end up in your tank is not maintained properly

  • Black Beard Algae aka Audouinella
  • Blanket Weed aka Cladophora Sp
  • Blue-Green Algae
  • Brown Algae
  • Fuzz Algae
  • Green Aquarium Water Algae
  • Green Dust Algae
  • Green Spot Algae
  • Hair Algae
  • Rhizoclonium Algae
  • Spirogyra
  • Staghorn Algae

Black Beard Algae aka Audouinella

This is a type of red algae, the hardest to get rid of. BBA is more common in saltwater setups but freshwater tanks are not safe from it either. It photosynthesizes to produce a protein called phycoerythrin, which is a black-purple in appearance.

It grows quickly and in patches and is also extremely tough to remove. Plants and most hard surfaces like driftwood or bogwood in your aquarium are not safe from this type of algae. Erratic light intensities and carbon dioxide levels are commonly held guilty for BBA.

Although you can get rid of audouinella manually by scraping, the most efficient method may be soaking the infected items in a dilute five to ten percent bleach solution.

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Blanket Weed aka Clapodhora Sp

Blanket Weed is from the green algae family and possibly might be the stoutest of all typical algae. It is found, usually, in freshwater habitats. Excessive sunlight, nutrients, and high pH are the mainly held culprits for blanket weed.

It forms a tough mat-like structure of wool strings or fiber and attaches itself to anything. The worst part is attempting to remove it by scraping, which gives off a pungent stench. It is almost impossible to manually remove it a hundred percent.

Blue-Green Algae

This one is commonly referred to but is not an actual alga; in reality, it is a type of bacterium called cyanobacteria. Cyanobacteria are a nitrogen-fixing bacterium which means it will eventually consume all of the nitrogen in your tank and thus, it should not be allowed to breed for long.

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It grows quickly to cover the substrate in the aquarium. Some species release toxins and may kill fish and are swallowed by them. It also has a unique earthy smell to it. They are typically blue-green but can also be brown, red, or even black, with a foul odor. When you try to peel it off, it falls off as sheets or clumps. The most famous and effective method to get rid of it is the ‘blackout’ method.

Brown Algae

This type of algae is usually found in newer tanks, especially freshwater and marine setups, and goes away as the aquarium matures and adjusts to a stable ecological cycle. They are a form of diatom (unicellular) and can survive in simple modest conditions if their chemical food is available.

That is because of their ability to photosynthesize as well as obtaining nutrients through nitrates and phosphates etc. Being diatom in nature they usually are not even noticeable, unless they start blooming rapidly.

Although it is not at all harmful, the algae bloom and covers the aquarium with a slime-like layer, which is not the best sight. Unlike cyanobacteria, brown algae do not come off in clumps and are not the hardest to remove; it can even be wiped off with a soft cloth!

Fuzz Algae

This type of algae is also, often, a sign of a young and imbalanced ecological system in new tanks. It grows as a single thread-like filament on your plants and glass, creating a fuzzy appearance.

The resemblance in appearance easily confuses it with Hair Algae, which grows denser compared to fuzz algae. If it appears in an older tank, it is an indication of macronutrient and carbon dioxide imbalance. Little amounts of it are harmless and can be left untouched, like most algae.

Green Aquarium Water Algae

This type of algae causes the tank water to turn green as it rapidly reproduces. The single-celled planktonic algae bloom to cause the very common hideous looking green water. Despite its appearance, a small amount of the alga is not toxic. It is caused by a spike in light intensity or nutrients.

Another interesting aspect, making it hard to deal with, is the fact that it does not settle on hard surfaces but floats freely in the water. Since it is a unicellular organism that replicates at extreme speed, changing tank water is not the way to eliminate it. A UV sterilizer or complete blackout for a week are way more effective methods.

Green Dust Algae

GDA is also common in newer aquariums with an imbalance in the ecological system. The term ‘dust’ sets it apart from other types of green algae since it can be wiped off with a finger or with water and settles at the bottom of the tank like a layer of loose dust.

It loosely coats the aquarium glass etc. The easiest method to get rid of it is by doing nothing. Yes, you heard it right! Let the aquarium sit and the algae boom for four weeks, at least. Until it completes a full life cycle. If disturbed, the algae release spores and restart the life cycle. - For all your creative needs!

Green Spot Algae

GSA is commonly confused with GDA. It appears as small, hard, flat green spots on your plants, glass, etc. It appears most in freshwater setups. Starting as small dots, they can eventually widen if not treated and given a favorable habitat.

They form extensive layers with time and attach to surfaces very firmly. They are frequently found in higher light intensity aquariums. Its main difference from GDA is that it is hard tougher to remove.

Hair Algae

Also known as thread algae. From the family of Oedogonium algae, this type of algae forms long and loose thread-like structures. It is also a type of green algae. The alga anchors itself to plants, usually, but also adheres to other items in the aquarium.

It is fast-growing and thus, can be tough to clear from the aquarium. Nutrient deficit or too much light are some causes of it. The algae can be easily removed if it is not securely anchored. When removed they are known to resemble wet hair, giving it its name.

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Rhizoclonium Algae

It is a genus of green algae, specifically a species from Cladophoraceae. It forms slimy and soft fibers that are brownish-green in color. Low water nutrients, carbon dioxide, and poor water flow are a few of the reasons which can trigger the growth of this type of algae. It is also a struggle to remove.


An alga from the filamentous green algae. It is quick in growth and forms long bright green strands that can extend to a great length. They are sometimes long enough to crowd up the tank.

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It is also an inconvenience to remove because it requires the same optimum conditions as your aquarium plants. It is hard to pinpoint an exact cause for this type of algae but the spike in ammonia levels due to dead organisms or infrequent water changes might be a few of the reasons.

Staghorn Algae

Belonging to the red algae group, this type is easy to distinguish. It grows shaped like a stag’s horn which earns its name. It is grey but will turn red if immersed in alcohol. The alga attaches itself very firmly to the tank equipment and plants. the threads of the alga grow thick and bushy overtime.

It is hard to remove manually and no algae eater fish are ready to eat it because of its hideous appearance. Low levels of carbon dioxide and poor water circulation are a few reasons triggering its growth. Excessive use of plant fertilizer, especially the ones containing high levels of iron, may also lead to it.

One question still stands, is there a way to getting rid of Algae?

The truth is, there is no full-proof method that prevents all types of algae infestation. Algae growth is natural and unavoidable. All closed aquariums, even if with the same type of plants and set conditions, have their unique ecosystems.

This makes it impossible to find one fixed reason behind your algae bloom. We must realize no algae free aquarium exists. Many of the alga being unicellular is unnoticeable unless it blooms rapidly. Although algae growth is not always harmful, it can be visually unappealing and even fatal.

This makes recognizing algae and controlling its growth a crucial skill for fishkeeping. Maintaining an aquarium is tedious, to say the least, but can also be fun once you get the hang of it.


This concludes the list of algae that you are most likely to interact with, as an aquarium owner. Now that you know your basic algae, it’s time to talk about some of the effects it has on the fish and the ecological system in your aquarium. Some algae are mandatory for a properly functioning ecosystem. They use up carbon dioxide and release oxygen like green plants.

They also help in minimizing the toxic form of nitrogen in your tank. Other types act as direct food for some of the fish. The point being, not all forms of algae are bad but too much of it is a different story.

They release toxins causing the death of any fish that consumes it, deplete oxygen levels in the tank after they die, and look unpleasant. Appearance plays a major role, especially when the tanks are for home decor which is why we strive so hard to keep all alga from blooming.