15 Types of Aquarium Algae – Causes, Treatment, And Prevention

All fish keepers are familiar with the curse of aquarium algae! 

Whether it’s the fuzz algae that coats your viewing panes, the thread algae and white hair algae that trail from your plants, or the staghorn algae that none of your fish will eat, you want to know how to get rid of algae.

So, what causes algae in your fish tank? How many types of aquarium algae are there? And how do you get rid of them for good?

Keep reading for the answers to those questions and more!

15 Types of Aquarium Algae – Causes, Treatment, And Prevention

Now, we’re going to take a look at 15 species of aquarium algae that commonly invade home fish tanks.  We’ve also included lots of helpful information on how you can prevent the slimy green menace from contaminating your aquarium in the first place!

1.  Black Beard Algae (Audouinella/Black Brush Algae/BBA)

What Is Black Beard Algae?

Black Beard algae (BBA) is a species of red algae (Rhodophyta) that’s most commonly seen in marine setups, although it can sometimes appear in tropical freshwater aquariums.

As it photosynthesizes, BBA produces a red light protein known as phycoerythrin, making the colonies appear black or dark purple algae.

This species of algae is notoriously difficult to get rid of, growing very rapidly and forming thick patches that resemble a beard. BBA will quickly spread in your tank to cover driftwood, hard surfaces, and even slow-growing living plants.

How To Get Rid Of Blackbeard Algae

• If the algae is growing on the viewing panes or filter equipment, use an algae scraper to remove as much as you can.
• Try overdosing the tank with Seachem Flourish Excel.
• If your plants and decorations are covered with BBA, make up a solution of 1:20 bleach and water, and dip the infected items into that for two to three minutes.
• Keep up with weekly water changes.
• Increase the amount of CO2 in your tank to boost plant growth and outcompete algae for nutrients.
• Improve the water flow around your tank by rearranging your aquascaping or upgrading your filtration system, or adding powerheads.

2.  Green Spot Algae (GSA/Coleochaete Orbicularis)

What Is Green Spot Algae?

Green Spot algae are so named for the tiny green spots it forms on everything in your fish tank, including plants, decorations, glass, and on filter equipment. In favorable conditions, this species of algae will spread to form extensive colonies.

Causes

• An imbalance of nutrients, typically in a new setup.
• Insufficient water changes.
• Poor fertilization.
• Phosphate depletion.
• Low CO2.
• Poor water circulation.
• Too much light or exposure to sunlight .

Green Spot Algae Eaters

• Sun snails (Clithon sp.)
• Nerite snails (Neritina sp.)

3.  Blanket Weed (Cladophora sp.)

What Is Blanket Weed?

Blanket Weed is a total nightmare to remove! 

The algae form a green, woolly mat that latches onto the substrate, hair grass, and hardscaping. If you attempt to scrub or rub Blanket Weed, it emits a very unpleasant odor.

Causes

• The introduction of poor quality plants to the setup, typically Marimo Balls.
• High levels of nitrates, light, and CO2.
• Healthy water conditions are favored.

How To Get Rid Of Blanket Weed

• Turn off the filtration system or any other form of water circulation so that you don’t inadvertently distribute the algae around the tank.
• Use a set of long aquascaping tweezers to pick out as much of the algae as possible.
• Spot-treat problem areas with Seachem Flourish Excel.
• Always quarantine new plants before introducing them to your main display tank.

4.  Fuzz Algae

What Is Fuzz Algae?

As you might guess from its name, Fuzz algae is a short, green, filamentous algae that grow over the viewing panes, ornaments, and plants, giving everything a fuzzy appearance.

It’s thought that Fuzz algae are an early growth stage of Hair algae, and a small colony in your aquarium is not a problem.

Causes

• Commonly seen in new setups that have an imbalance of nutrients.
• Nutrient imbalance and low CO2.

How To Get Rid Of Fuzz Algae

• Test your aquarium water for CO2 and nutrient levels and make any necessary adjustments
• Create the perfect environment for your plants to encourage them to outcompete the algae
• Introduce a clean-up crew of algae-eating critters (see below)

5.  Blue-Green Algae

What Is Blue-Green Algae?

Blue-Green algae are actually not true algae but a species of aquatic cyanobacteria that can photosynthesize. This interesting “algae” is also a nitrogen-fixing bacteria, which will eventually absorb all the nitrogen that your tank water contains.

Blue-Green algae grows very quickly, eventually coating everything in the tank in a reddish-purple, blue, brown, or dark green slime. You often find Blue-Green algae growing on the substrate or on the glass where it gets the most light.

Causes

• High levels of organic waste matter and or insufficient water changes.
• Too much light.
• Old light bulbs that don’t provide sufficient light for your plants, leaving them unable to outcompete the algae for nutrients.
• Poor water circulation.

Blue-Green Algae Eaters

There are no known Blue-Green algae eaters.

6.  Hair/Thread Algae

What Is Hair/Thread Algae?

Hair/Thread algae is a type of filamentous algae that forms long, green threads that look like flowing hair.

This species of algae usually fixes itself to plants, although it sometimes grows on the substrate and aquarium decorations.

Causes

• Oversaturation of nutrients, typically too much iron or too much light.
• Too much light and insufficient nutrients.
• CO2 or nitrate deficit.

Hair/Thread Algae Eaters

• Amano Shrimp
• Mollies
• Dwarf Shrimp (Red Bee or Red Fire Shrimp)
• Siamese Algae Eater
• Florida Flag Fish

7.  Brown Algae (Diatoms)

What Is Brown Algae?

Brown alga is a form of diatom that uses silicate, nitrates, and phosphorus, as well as photosynthesis to obtain the nutrients it needs. That means the algae can survive in conditions where light is poor, provided that the chemical food is available.

Brown algae is found in both saltwater and freshwater fish tanks, first appearing as a light dusting on the substrate. Within five days, the diatom morphs into a disgusting slimy coating that covers your aquarium glass, plants, and substrate.

Causes

• Insufficient lighting.
• High levels of nitrates, silicates, or phosphorus and or low oxygen levels.
• Immature fish tanks where the biological filter hasn’t completely matured.

Brown Algae Eaters

• Otocinclus Catfish
• Plecostomus
• Yellow Tangs

8.  Rhizoclonium Algae

What Is Rhizoclonium Algae

Rhizoclonium algae is a form of green algae belonging to the Cladophoraceae genus. This slimy, soft alga grows in fine brown or green hair-like strands rather like Hair algae.

Causes

• Poor general tank maintenance.
• Low levels of CO2 and nutrients.
• Inadequate water circulation.

Rhizoclonium Algae Eaters

• Amano shrimp

9.  Green Dust Algae (GDA)

What Is Green Dust Algae?

Green Dust algae are sometimes confused with Green Spot algae, but GDA grows in green, slimy colonies over the viewing panes of your aquarium, whereas GSA grows in spots.

Causes

• Common in new setups that are not fully cycled.
• Can appear mature tanks where CO2 and nutrients are low or out of balance.

Green Dust Algae Eaters

• Bristlenose plecos

10.  Spirogyra

What Is Spirogyra?

Spirogyra is named for its spiral-shaped chloroplasts. These algae form long, fine, slippery bright green strands that can spread throughout your fish tank.

Causes

• Ammonia spikes caused by overfeeding, inadequate water changes, dead livestock, and dirty filters.
• High concentrations of micronutrients, such as iron.
• Too much light.

Green Dust Algae Eaters

• Rosy barbs

11.  Oedogonium Algae

What Is Oedogonium Algae?

Oedogonium presents as short, green, free-floating, filamentous algae that cling to your plants, giving them a fuzzy appearance.

Causes

• Low nutrients and CO2.

Oeodogonium Algae Eaters

• Rosy barbs
• Amano shrimp
• Mollies

12.  Free-Floating Algae

What Is Free-Floating Algae?

Free-Floating algae are tiny unicellular organisms that float freely in the water column without attaching themselves to anything, turning the water a cloudy green color.

Causes

• Too much light, especially sunlight.
• An overabundance of nutrients.
• Insufficient or irregular water changes.

Free-Floating Algae Eaters

• Shrimp
• Snails

13.   Staghorn Algae (Compsopogon sp.)

What Is Staghorn Algae?

Staghorn algae are one of the red algae and are so named because it grows to resemble a stag’s antlers. This species of algae generally attaches itself to plant leaves, filter boxes, and tank decorations.

Causes

• Low CO2.
• Poor water circulation.
• Excessive nutrients caused by overfeeding or poor tank maintenance.
• Ammonia spikes, especially in new tanks that haven’t fully cycled.

Staghorn Algae Eaters

Unfortunately, no self-respecting critter will touch Staghorn algae!

14.   Red Slime Algae

What Is Red Slime Algae?

Red Slime algae are actually a species of Cyanobacteria. This form of algae grows as a slimy red film, covering decorations, equipment, and glass.

Causes

• Elevated waste levels, including nitrates and phosphate.
• Poor water circulation.
• Old light bulbs or inadequate lighting.

Red Slime Algae Eaters

• Blennies
• Tangs
• Crabs
• Sea urchins
• Snails

15.   Green Aquarium Water Algae

What Is Green Aquarium Water Algae?

Green Aquarium Water algae are single-celled organisms that float freely in your fish tank, turning the water bright green. Thankfully, this pea soup is not harmful to your fish. Unfortunately, this form of algae replicates incredibly quickly.

Causes

• Ammonia spikes.
• Too much light, especially sunlight.
• Nutrient overload caused by overfeeding or infrequent water changes.
• New tank syndrome in tanks that are not fully-cycled.

Green Aquarium Water Algae Eaters

• Snails
• Shrimp

Tips To Avoid Algae

Although pretty much every fish tank has some form of algae growing in it, there are ways in which you can keep the degree of algae infestation under control.

Don’t Overfeed Your Fish

The primary cause of algal bloom in fish tanks is overfeeding. 

Blue-green and red algae typically multiply when large quantities of dissolved organic matter are present in the aquarium. Nitrates and phosphates are also a problem when fish are overfed, and those substances provide a food source for algae.

Feed your fish only what they’ll eat in two to three minutes, and remove any uneaten food with a fish net or aquarium siphon before the food has the chance to start decomposing and leaching algae nutrients into the water.

Raise The Competition

Algae use nutrients in the aquarium water in the same way as aquarium plants. So, you can raise the competition for food by including plenty of living plants in your setup, effectively starving the algae out.

Bottom line: keeping living plants in your fish tank will reduce the likelihood of algae overgrowth.

Keep On Top Of Water Changes

You should be carrying out partial water changes in your fish tank each week to maintain a safe, healthy environment for your fish. But regular water changes are also crucial in the fight against algae. 

Test Your Water Source

Tap water is treated with various chemicals to make it safe for you to drink and wash in. As you know, chemicals such as chlorine and chloramine are highly dangerous to fish, which is why you must use a water conditioner to treat the water before you add it to your aquarium.

However, did you know that tap water also contains substances such as phosphate and even nitrates? Test your tap water or well water to see what potential nasties it contains and either treat the water to make it less appealing to algae or find another water source, such as Reverse Osmosis (RO) or filtered water.

Algae Removal: Dos and Don’ts

There are a few dos and don’ts that you need to know about algae removal and control.

Don’ts

First of all, let’s take a look at the don’ts:

Don’t Settle For “Easy Fixes”

“Easy fixes” to an algae problem typically don’t prove effective in the long term, simply because they don’t address the problem that caused the outbreak in the first place.

For example, keeping your fish tank lights off for a few days will certainly wipe out algae. However, if you forget to carry out water changes, the tank will quickly become overloaded with nutrients, and the algae will return as soon as you turn the lights back on.

Don’t Be Scared Of A Little Algae

Many fish enjoy grazing on certain species of algae, and some types of algal growth can even add an attractive natural vibe to your setup.

So, don’t panic if you discover a few algae growing in your fish tank when you come to clean your viewing panes; that’s completely normal. After all, that’s why algae magnets and scrapers are sold in fish stores!

Dos

Here’s what you can do to keep down levels of algal growth.

Use Live Plants

There are lots of easy-to-grow aquatic plants to choose from, so don’t be afraid to include plenty in your aquarium.

Plants are your allies in the fight against algae, as they outcompete the algae for nutrients, helping to keep algal growth to a minimum. Plants also produce oxygen and use carbon dioxide as they respire, helping to keep the water well oxygenated for your fish. 

Finally, many shy fish species enjoy sheltering amid lush planting, which can also be a life-saver for vulnerable fry.

In Conclusion

Did you enjoy our guide to 15 different types of aquarium algae and how to treat and prevent it? If you did, please share!

Most forms of aquarium algae appear because of excess lighting, poor tank cleaning and maintenance practices leading to an overabundance of nutrients, and introduction of living plants.

Dealing with most species of algae is relatively simple, as described above. And the addition of a cleaning crew of algae-eating critters is a great way to keep algae growth under control.