15 Types of Aquarium Algae – Causes & How to Get Rid

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Written By Matt Stevens

Hi, I'm Matt! I've been obsessed with fishkeeping for over 15 years now and created this site to share my knowledge with others.

We know it. The curse of different types of aquarium algae. Sometimes so severe, it almost looks unmanageable.

But where does aquarium algae come from? Is there a simpler way to control their growth inside the tank? And which varieties should you expect inside a standard aquarium?

Find it all in this guide as we review the 15 types of algae you will almost certainly come across at some point in your aquarium hobby.

1. Green Spot Algae

Green Spot Algae is one of the most common types of algae you will ever see inside your tank.

 Green Spot Algae

While moderate growth of Green Spot Algae is considered normal, it can easily become a nuisance, spreading quickly all over the place to take over your aquarium.

Green Spot Algae has a circular shape and appears as green spots, latching onto the tank surfaces. They are primarily caused by excess nutrients and light inside the tank.

Like most aquarium algae, you can adopt a few important strategies to control the growth of the Green Spot Algae inside the tank. These include performing frequent water changes, cleaning your aquarium regularly, and avoiding overfeeding.

Of course, it’s always important to give prompt attention to sudden algal growth inside the tank to control its spread.  

2. Fuzz Algae

Fuzz Algae is usually described as short, green-colored filamentous algae that can grow on the tank decorations.

Fuzz Algae

You will find them on the glass, plants, and other decorations, forming a thick coat that can be bothersome without proper intervention.

Fuzz Algae are green fuzzy algae in a fish tank, something not commonly seen with other types of aquarium algae.

Despite the striking similarities, it’s important to note that these algae aren’t the same as the hair algae, and you should suspect reduced tank water quality when you first spot them inside the tank.

While low amounts of Fuzz Algae inside the tank is normal, you don’t want it to take over your beautiful aquarium with its limitless growth.

Fortunately, you can always control their growth by introducing suitable fuzzy algae eaters like shrimps. Also, general tank cleanliness, frequent water changes, and frequent oxygen and nutrient level check could be vital in limiting the algal growth inside the tank.

3. Blanket Weed Algae

Blanket Weed Algae is a name you will often hear in the aquarium community, and that’s because it’s known to cause endless problems to aquarists.

Blanket Weed Algae

It is many aquarists’ biggest nightmare, and if you are unlucky enough to face it, complete elimination from the tank will be a hassle. They appear as a green-colored wooly mat attached to the hair grass, substrate, and plants.

The worst part is that any attempt to remove the Blanket Weed Algae will be met by a bad smell, making the entire task even more taxing.

While we could go on and on to mention its disadvantages, never forget that opting for poor water quality aquatic plants is one of the most common causes of this type of algae in aquariums. That group includes rare plants like the Marimo Balls.

On top of that, excessive light, CO2, and nitrates have also been linked to Blanket Weed algal growth.

As for the treatment options, start by switching off the filtration system because you don’t want to end up spreading the bad-smelling algae all over the place. Also, be sure to quarantine any new plants before slowly including them in your aquarium.

4. Brown Algae

Brown Algae is one of the most difficult types to clear at home. And that’s because they can tolerate low lighting conditions as long as they find the right chemical food.

Brown Algae

They rely on photosynthesis in addition to phosphorus, nitrates, and silicates to get the essential nutrients they so badly need for survival.

What’s more, Brown Algae thrive in both saltwater and freshwater conditions, making them such a tough one to eliminate from the very first time you spot them inside the tank. 

They will want to attach to the substrate before turning into a stubborn coating within just a few days and spreading all over the plants and tank glass.

Typically, Brown Algae is caused by low light inside the tank, excessive nitrates, phosphorus, and silicates, reduced oxygen levels, and poorly maintained aquariums.

As for the safe elimination strategies, removing these algae using a vacuum, besides performing frequent water changes and increasing the light levels is essential.

Also, you can introduce dissolved oxygen into the water and deny the algae the essential nutrients.

And by the way, the Otocinclus, Yellow Tangs, and Plecostomus species can help reduce the brown algal growth inside the tank. So, you can use them to create a perfect ecological balance.

5. Black Beard Algae

Black Bear Algae or simply BBA is probably more common in saltwater conditions, but that doesn’t mean it can’t affect your freshwater setup. It appears in groups, like a dark purple or black algae that can be so irritating to deal with.  

Black Bear Algae

They are extremely challenging to eradicate, considering their rapid growth that can easily take over the entire tank.

It will be even more challenging if you let them form the thick beard-like pattern in severe cases. Like most algae on our list, BBA can easily spread all over the tank, covering your plants, hard surfaces, and even driftwood.

Of course, there’s nothing unusual with the specific causes. And just like most algae, the Black Beard varieties result from a nutrient imbalance inside the tank, phosphate decline, reduced CO2, and excessive light.

Also, it is directly linked to infrequent water changes and improper circulation.

Even though this will be difficult, you can eliminate the Black Beard Algae manually using an algae scraper or adopting a weekly water change routine. Other important strategies include enhancing the water flow and raising the CO2 level inside the tank.

6. Green Dust Algae

Green Dust Algae is the closest thing you will find to the aforementioned Green Spot varieties. However, it appears as a thin, green-colored film in colonies.

Green Dust Algae

It firmly attaches to the tank walls and rocks, making it just as challenging to deal with.

Green Dust Algae is always common in new tanks but grows in mature aquariums with reduced CO2 and nutrient supply.

While manual removal seems inevitable when controlling Green Dust Algae, complete elimination requires much more than just that. 

An ideal routine should target the entire algal film inside the tank. So, during the first four weeks, let Green Dust Algae run its complete lifecycle by simply monitoring its growth while taking no action.

Then, perform the first water change when this period elapses (4 weeks), targeting the lowest levels possible before scrubbing off the algae from the tank glass.

7. Red Slime Algae

Contrary to common beliefs, Red Slime Algae is not an actual alga. It is more of cyanobacteria, acting as an intermediary between the actual algae and the bacteria.

red slime algae

As their name suggests, Red Slime Algae appears as a red, slimy cover inside the tank, spreading on the tank glass and other decorations.

Red Slime Algae are more common in saltwater aquariums, and you should adopt the right strategies to limit their spread inside the tank.

While most species are typically blue-green, the most popular Red Slime found in saltwater conditions will have varied colorings, such as deep purple to black, orange-yellow to red-brown, and brackish green to blue-green.

Usually, they are linked to increasing waste levels inside the tank, improper tank water circulation, and insufficient lighting.

To control their spread, start by adjusting the nitrate and phosphate levels before improving the water circulation and enhancing tank cleanliness.

8. Green Aquarium Water Algae

Green Aquarium Water Algae isn’t the most common name you will hear in the aquarium hobby, but still, serious enough to warrant your attention.

Green Aquarium Water Algae

It presents with green-colored water, almost resembling a dye inside the tank.

It is caused by the free-floating algae all over the tank, sometimes so severe you won’t even spot your favorite pet fish.

In the cases of rapid growth inside the tank, the first suspect will be excessive light. Next, be wary of the increasing amounts of nutrients inside the aquarium.

Lastly, infrequent tank cleaning could play a role in algal growth inside the tank. The safest way to eliminate this form of algae is to opt for a complete tank blackout for a minimum of 3 days.

That way, it’s easier to facilitate the algal death within three days and return normalcy inside the tank.

9. Staghorn Algae

Staghorn is another common type of red algae that grows by attaching itself to the tank decorations, plant leaves, and other equipment.

Staghorn algae

They are easily noticeable by the characteristic stag horn-like appearance. Unfortunately, they are also one of the most difficult algae to deal with, especially when considering manual techniques like scraping.

Staghorn Algae aren’t appealing to most algae-eating critters, putting all the responsibility on your shoulder from the get-go. Typically, Staghorn algae are caused by reduced CO2 levels inside the tank and improper circulation, ammonia increase, and poor tank maintenance.

As for the general elimination methods, you can consider manual techniques like scrubbing or opt for proper tank cleaning to improve hygiene.

Besides, aquarists have had success by improving the general water circulation, sometimes going as far as bleaching the affected surfaces with a water solution.

10. Free-floating Algae

As their name suggests, free-floating algae refer to any organism floating effortlessly on the water surface.

 free-floating algae

Of course, these are always single-celled organisms that can latch onto hard surfaces, creating an unattractive green cover inside the tank.

Such algae are caused by excessive light and nutrients and insufficient water changes. Usually, you can eliminate them by going on a complete blackout for three days or using a perfect UV sterilizer.

While it never guarantees success, you can also turn to suitable helpers like the snails and shrimps to help eliminate such types of algae from the aquarium.

11. Oedogonium Algae

Oedogonium is a green, filamentous alga that W. Hilse first described sometime in the 1860s. It typically exists in quiet water bodies either latched onto other plants or as free-floating algae.


Its clingy nature gives it a characteristic, fuzzy appearance primarily caused by low CO2 concentration and other nutrients inside the tank.

The safest way to get rid of Oedogonium algae is by adjusting the tank’s CO2 and other nutrient levels. On top of that, you can overdose the tank with a suitable treatment agent.

Another biological method for eliminating this type of algae is introducing common Oedogonium algae, lovers like the Amano Shrimps, Rosy Barbs, and Mollies to the tank.

12. Spirogyra

Spirogyra rightfully gets its name from the beautiful chloroplasts taking on a helical or spiral-like pattern.

Spirogyra algae

Their long, slippery strands can easily spread all over the tank, making them a tough one to deal with from the onset.

You will see an influx of Spirogyra inside the tank with increasing ammonia levels, always resulting from infrequent water changes, dirty filters, and leftover fish food.

But sometimes, these algae indicate excessive micronutrients and light inside the tank. As for the preventive measures, start with a total blackout for three consecutive days following the initial identification of the specific algae inside the tank.

Besides, you can resort to effective water changing or simple tank overdosing using suitable treatment methods.

13. Hair Algae

Like their name alludes, the hair algae, sometimes called the thread algae, is another common soft green algae with a hair-like appearance.

hair algae

They readily attach themselves to the tank decorations, sometimes spreading all over the substrate to become a nightmare for your active fish.

Hair algae have three primary causes, including CO2 and nitrate deficiency, excessive aquarium light, and high nutrient concentrations like iron.

Instinctively, you will want to improve the nutrient levels inside the tank to eliminate unwanted growth, which is the safest approach to take at any given time.

But for a more comprehensive approach, you may want to remove the algal growth manually, test and change the tank water frequently, and even introduce natural hair algae eaters like the Mollies, Amano Shrimps, and Dwarf Shrimps.

All in all, stick to what matches your preferences while still giving the best results.

14. Blue-Green Algae

Like Red Slime Algae, the Blue-green variety is a cyanobacterium that can spread rapidly inside the tank.

blue-green algae

They are famous for their impressive nitrogen uptake abilities and will always appear as a dark green, brown, blue, or reddish-purple coating inside the tank.

Usually, the blue-green algae grow on the tank glass, substrate, and any other surface that can help them obtain plenty of light. Like most algae, the blue-green variety increases with harmful organic waste, excessive light, and improper water circulation inside the tank. 

To easily get rid of them, ensure you blackout the aquarium for at least three days before treating the affected areas with a suitable agent.

Other simple strategies include enhancing the tank water circulation and overdosing the aquarium as advised by an expert.

15. Rhizoclonium

Rhizoclonium completes our list of the 15 most popular aquarium algae, as a slimy member of the Cladophoraceae family that readily assumes a hair-like appearance.

Rhizoclonium algae

Their general appearance mirrors the typical hair-like algae, even though they can take on green or brown coloring.

Typically, Rhizoclonium algae thrive from improper tank maintenance, low nutrient and CO2 levels, and improper water circulation.

Fortunately, you can limit its growth by increasing the CO2 levels, maintaining general tank cleanliness, or overdosing the aquarium the right way.

Final Thoughts

So, that’s it. As you can see, almost all aquarium algae types are related to reduced tank water quality, excessive lighting, or high concentrations of nutrients. So, the easiest way to counter their growth at any given time will be to adopt an effective cleaning routine.

We hope you will find our guide worthwhile the next time you’re faced with an unappealing sight of freshwater aquarium algae. If you still can’t figure out how best to handle unwanted algal growth, we will be ready to help.