13 Types of Aquarium Algae – Causes & Treatments

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Algae are considered a pest when they get out of control, but as you will learn from this article, algae can also be beneficial for your aquarium.

One thing is certain, however: algae are present in any body of water, and while there are ways to control them, it’s impossible to completely avoid them.

In fact, there are over 8,000 species of algae present on earth, so whether you’re keeping your fish in a freshwater tank or saltwater tank, you’re bound to run into algae issues at some point.

If you’re taking up aquarium husbandry for the first time, algae are something that you should learn about, especially the ways to keep them under check.

In this guide, I will discuss common algae types, their causes, how you can remove them from your aquarium, and some prevention tips.

By the end of this article, I hope you’ll be able to identify the algae present in your tank and you will know how to manage them.

Algae Types & Causes & How to Get Rid of Them

I’m going to discuss over 10 algae types with special focus on their causes and give you tips on how you can remove them from your tank.

Let’s start with one of the most feared type of algae:

1. Green Aquarium Water Algae

This common freshwater aquarium algae turns your water opaque green, and it can sometimes overtake the tank to the extent that it reduces the transparency of water.

It looks terrible, for sure, but luckily, it’s not toxic to your fish.

These types of algae grow through the photosynthesis of light and as a unicellular organism they’re rate of replication is crazy fast.

What Causes It?

There are two common causes of green aquarium water algae – excess light and nutrients.

Since these plants photosynthesize light, tanks with exposure to direct sunlight are more prone to algae blooms.

On the other hand, excess organic waste, whether it results from too many fish being housed in the tank or leftover food from overfeeding the fish, acts as a nutrient to algae, which can lead to their bloom.

You can encounter algae blooms even during the nitrogen cycle of your tank when there aren’t enough bacteria to transform ammonia into nitrites.

How to Remove It?

Some guides will recommend more frequent water changes, which may reduce its levels, however, it won’t prevent it from developing again.

What you need to do is address the underlying cause.

If your tank is exposed to too much direct sunlight, cut off any access to light for a week. However, this method can be hard on your plants, so an alternative would be to use an UV sterilizer.

Next, you should introduce green water algae eaters into the tank like snails, shrimp or daphnia.

As with many issues, prevention is best when it comes to algae. To this end, I recommend that you:

  • Clean your tank regularly;
  • Avoid direct sunlight to the tank;
  • Avoid overfeeding your fish;
  • Avoid housing too many fish in your tank;
  • Use an UV filter.

2. Black Beard Algae

Also known as Audouinella or Black Brush Algae, the Black Beard Algae is a type of red algae that’s more prevalent in saltwater, but sometimes it may appear even in freshwater tanks.

The reason for the name of these algae is their black/purple color, which is caused by a red light protein that is produced as a result of photosynthesis.

The Black Beard Algae has a soft, slippery texture and grows in dense patches. It’s difficult to remove and it will develop mostly on plants, driftwood or any other hard surface in your aquarium.

What Causes It?

Several things can cause these algae types to appear in your tank including:

  • Unstable CO2 conditions that prevent plants from using fertilizers and light to undergo photosynthesis, which favors this type of algae;
  • Contaminated plants introduced into the tank.

It has been suggested that water flow can be another cause for BBA, but aquarists have reported experiencing BBA growth in both high-flow and low-flow waters.

How to Remove It?

First, check to see if CO2 levels in your tank are within the recommended range. If levels are low, you need to increase CO2 to stimulate plant grow that can compete with algae for resources.

Next, you can attempt to manually remove algae from the surfaces in your tank. Use elbow grease, get an algae magnet or scraper and go at it.

You can soak plants and other items in your tanks affected by this alga in a 10% bleach solution for 2-3 minutes, but make sure you remove any traces of bleach before putting them back into the tank.

You can use Seachem Flourish Excel or Metricide if you’re really struggling with the removal.

Introducing Black Beard Algae eaters to the tank like Siamese Algae Eaters, Amano Shrimps and Florida Flag Fish is another way to deal with this type of algae.

Here too, prevention is crucial:

  • Quarantine new fish for a couple of days before introducing them to the tank;
  • Don’t dump fish straight out of the bag to avoid any contaminated water getting into the tank;
  • Soak new plants in a 10% bleach solution to kill off any algae on them.

3. Blue-Green Algae

Technically, Blue-Green Algae isn’t an alga but a cyanobacteria that’s also called Slime or Smear Algae, and for good reason.

Blue-Green Algae grow fast and cover everything in sight, coming off in sheets when attempting their removal. It’s both slimy and stinky, giving off an unpleasant fishy odor.

When I say it can cover everything in sight, I mean everything including the substrate of your tank and can accumulate as a foamy scum at the surface of the water.

In terms of color it can be green, blue, brown or reddish purple.

They’re also able to photosynthesize and as a nitrogen-fixing bacterium they can use up your aquarium’s entire supply of nitrogen.

What Causes It?

As with many other types of algae that I’m going to discuss in this article, the causes of Blue-Green Algae are:

  • Excess light can cause these cyanobacteria to thrive;
  • Excess waste from overfeeding your fish and a lack of water changes;
  • Introducing items into the aquarium that were contaminated with Blue-Green Algae.

I mentioned that Blue-Green Algae can fix nitrogen, so they can appear even in well-maintained and mature tanks.

How to Remove It?

Unfortunately, once Green-Blue Algae appears in your tank, it’s not easy to eradicate.

Here are some things you can try if you notice GBA algae in your tank:

  • Reduce/completely block light;
  • Frequent partial water changes;
  • Physical removal (scrape glass, scrub rocks, vacuum the substrate);
  • Use Erythromycin.

Algae eaters unfortunately will not eat Green-Blue Algae, so you’re stuck with physically removing it or dosing it with products containing Erythromycin.

To prevent algae growth, take regular maintenance of your tank seriously. Avoid overfeeding your fish as an excess of nutrients can cause all sorts of algae blooms.

4. Blanket Weed

If you’re dealing with this alga, my sympathies. Not only that Blanket Weed is notoriously hard to remove, it’s also terribly stinky when scraped.

It appears as a wool-like mat that covers grass, substrate and hardscape items in your tank. It has a green color and it’s important to remove it as soon as it appears in your tank to avoid a full-blown infestation.

What Causes It?

Contamination through plants that you introduce in your tank is the most common cause of Blanket Weed. Other causes include high levels of nitrates in your tank, excessive light, and CO2.

There’s also the problem of it preferring the healthy water conditions that aquarium plants prefer, an aspect which makes it even more difficult to remove.

How to Remove It?

Let me preface this by saying that chances are you can’t remove all Blanket Weed algae from your tank, so again, prevention should be your first line of defense. Plus, there’s nothing that will eat it.

Still, if it appears in your tank, you have to deal with it asap.

Things you can attempt is to is to physically remove as much as you can with long tweezers. Following this, spot treat problem areas with Excel by using a syringe.

Make sure to turn off the current in your tank to avoid spreading it everywhere.

As for prevention, be extremely careful when introducing plants in your tank and do your best to sanitize them or in the very least quarantine the plants before adding them to the aquarium.

5. Brown Algae

This is another alga that appears as a slimy film on glass, substrate or the plans in your tank. It grows quickly and it’s especially prevalent in new freshwater tanks during the nitrogen cycle.

It first starts out as brown patches on the gravel or glass in your tank and it develop into a full-blown problem in a matter of 5 days.

Luckily, it’s not difficult to remove and it’s even easier to prevent.

What Causes It?

Brown algae can be caused by any of the following things or combination of things:

  • High levels of phosphorus, silicates, and nitrates (these algae can obtain nutrients through photosynthesis and chemicals);
  • Inadequate lighting levels (too little or too much light);
  • Low oxygen levels.

Silicates can build up in your tank from tap water or can leach from certain substrates. Nitrates, on the other hand, can result from excess waste or uneaten food.

How to Remove It?

Because Brow Algae doesn’t adhere strongly to the surface of the tank, so there’s no scrubbing of surfaces, you can easily wipe it away.

To remove Brown Algae:

  • Clean the tank by wiping all surfaces and vacuum the gravel;
  • Use partial water changes to remove and dilute some of the nutrients feeding the algae;
  • Adjust the lighting of your tank, so it gets 6 to 8 hours a day;
  • Use silicate absorbing resin in your filter media;
  • Introduce Brown Algae eating fish like Plecostomus, Otocinclus fish, and Yellow Tangs;
  • If the problem is caused by lack of oxygen, slowly lower the temperature if water is too warm, or add an air pump to your tank.

As you can see, there are plenty of things you can do to remove Brown Algae from your aquarium.

In terms of prevention, you can use reverse osmosis water instead of using tap water and make sure you regularly clean the tank and perform water changes.

6. Fuzz Algae

Often confused with Hair Algae, Fuzz Algae appear as short individual filaments of green color growing on plants, aquarium glass and decorations. They have a fuzzy appearance, hence the name.

Fuzz Algae commonly appear in tanks that have yet to mature. You’ll commonly notice them during weeks 4 to 8. A small population of Fuzz Algae in your tank is no cause for concern.

What Causes It?

A disturbance or imbalance in a young ecological system is the most common cause of Fuzz Algae growth in a tank.

Low CO2 can be another cause for this alga, preventing plants from competing for resources with algae.

It’s not unheard of for Fuzz Algae to suddenly appear in a mature tank as well. When this occurs, it’s usually because of an imbalance of macronutrients (nitrate, phosphate, potassium).

How to Remove It?

Check to see if nutrient levels and CO2 levels are within the target values for your tank. If not, adjust accordingly.

Another thing you can do is to create a healthy environment for your plants to thrive in, because Fuzz Algae are easily outcompeted by healthy and fast-growing aquatic plants.

Alternatively, you can introduce a clean-up crew that consists of Amano Shrimp, Siamese Algae Eaters, Bristlenose Plecos, Otocinclus, and Black Mollies.

When Fuzz Algae are attached to the substrate, it’s difficult to remove manually, but you can easily scrape them off your aquarium glass.

7. Green Dust Algae

Green Dust Algae is an algae type that form a slimy coat on the glass surfaces of the aquarium.

This alga bonds to surfaces very loosely and they’re easy to remove even by simply moving your finger on the surface of the glass.

It’s sometime confused with the Green Spot Algae, but as its name suggest, this type of alga grows in spots, while the Green Dust Algae settles everywhere in your tank, very much like dust.

What Causes It?

Green Dust Algae are most likely to appear in new tanks that are still undergoing their nitrogen cycle and beneficial bacteria are yet to colonize the tank.

When they suddenly appear in a mature tank, it’s most likely caused by drastic changes in the water chemistry, technical equipment or plant mass.

Changes in light or peaks of nitrogen can easily trigger a Green Dust Algae infestation. Imbalances in nutrients and CO2 levels can also cause this alga to get out of hand.

How to Remove It?

Probably the most efficient way to address a Green Dust Algae infestation is to sit it out. Yes, that’s right, you read that right – simply let it run its lifecycle without doing anything.

It will take approximately 3 to 4 weeks for it to complete its cycle. In the meantime, it’s important not to try to remove it, because it will release spores and restart its lifecycle.

After the lifecycle has ended, you’ll notice that algae coats get incoherent. At this point, you can perform a water change and lower the water level in your tank as far as possible and wipe algae off the glass.

Others may go as far as doing a complete clean-up of their tank with hydrogen peroxide, but I found that there is no need for such drastic measures and the method described above will usually solve the problem.

Introducing algae-eating fish like Bristlenose Plecos can also help both to prevent and remove Green Dust Algae.

8. Hair/Thread Algae

If you notice soft and loose green threads in your tank, you’re dealing with Hair/Thread Algae.

It can be a nuisance and if you don’t take immediate action as soon as it gets a foothold in your tank, it will soon take over everything, and you’re going to have a hard time getting rid of it.

They prefer getting attached to the plants in your aquarium, but they’ll also anchor themselves to decorations, gravel and the glass of your tank.

I personally hate this type of algae with a vengeance, because it has a wet hair feeling when you’re removing it from the tank and it grosses me out.

What Causes It?

Excess light (it can be caused by something as simple as installing a new light source) or an excess of nutrients in your aquarium.

They can appear during the nitrogen cycle of a newly set up tank, when the microbiology of the tank is still unbalanced.

A nitrate or CO2 deficit can also be blamed for the appearance of this type of algae. When your tank if low in nitrates, plants that could compete with algae for resources could stop growing.

How to Remove It?

Starving out Hair Algae is one way to remove it from your tank. You can do this by adjusting nutrient levels in your tank and by promoting aquatic plant growth that can take away resources from these algae.

Next, you can stock up on algivores like Dwarf Shrimp, Amano Shrimp, Florida Flag Fish, Mollies, Siamese Algae Eaters that will keep your tank clean and tidy when it comes to algae.

Alternatively, you can manually remove Hair Algae. Those loosely anchored will come off quite easily, the stronger ones you’ll need to wind onto a skewer with a rough surface.

When it gets out of hand a blackout treatment or the use of algicides can be a last resort treatment option.

9. Green Spot Algae

Common in freshwater aquariums, a small amount of Green Spot Algae in your tank is normal and expected, but an overgrowth should be prevented or treated.

As its name suggests, Green Spot Algae first appears as tiny green spots on pretty much any surface in your tank – decorations, plants, glass, etc.

When they extend, they form extensive coats and adhere strongly to hard surfaces.

What Causes It?

The potential culprits for the appearance of such algae are:

  • A nutrient imbalance in a newly set up tank;
  • Depletion of phosphates;
  • Lack of weekly water changes;
  • Inadequate fertilization;
  • Low CO2;
  • Too much light exposure;
  • Poor water circulation.

Any of these or a combination of these can be blamed for Green Spot Algae.

How to Remove It?

Managing the causes listed above can help in preventing an overgrowth of Green Spot Algae.

The most common cause for this alga appearing in your tank is a depletion of phosphates, so I recommend starting there. Measure phosphate levels and adjust levels accordingly.

Next, you can physically remove green spot algae with a scraper and see if it returns.

You should also check the number of hours your tank is getting lighting. Make sure it’s no more than 9 hours.

You should also introduce Green Spot Algae eaters to your aquarium that will help keep it under check. Good algivores for this type of algae are Sun Snails and Nerite Snails.

10. Oedogonium Algae

An exclusively freshwater algae, the Oedogonium is a short filamentous alga that has a green, fuzzy appearance and attaches itself to other plants. Mature filaments exist as a free-floating mass.

What Causes It?

As with many other algae, the Oedogonium appears as a result of a nutrient imbalance and low CO2.

How to Remove It?

The good news it this alga is not as stubborn as other and can be removed by adjusting nutrient levels and CO2 in your tank.

There are also some algae eaters that can help prevent Oedogonium Algae from overgrowing and will keep your tank nice and clean. These are: Amano Shrimps, Mollies, and Rosy Barbs.

11. Spirogyra

Spirogyra is another alga that can be a real nuisance, especially because it thrives in the same healthy water conditions as your aquatic plants.

They’re a filamentous green alga with very long, fine spiral strands that grow fast and can overtake the entire tank.

What Causes It?

Unfortunately, since it can appear even in stable environments, there aren’t any exact causes for their appearance.

Therefore, the common causes for any algae bloom apply for this type of algae as well:

  • High ammonia levels caused by overfeeding, dead fish, dirty filters or lack of water changes;
  • Excess nutrients (especially iron);
  • Excess light.

Unfortunately, it can be difficult to clear this alga, but there are some solutions that can help.

How to Remove It?

Since there is still a debate to the exact causes of Spirogyra, its removal can also be a trial by error undertaking.

You could try the following methods or combination of methods to see which works:

  • Manual removal;
  • 3-day complete blackout with CO2 turned off, followed by dosing with Excel, TNC Carbo or Easy Carbo;
  • Frequent and large water changes followed by dosing with Macros;
  • Hydrogen peroxide treatment;
  • Stocking the tank with algae eaters (Rosy Barbs).

12. Rhizoclonium Algae

This alga is another one that can be difficult to remove and it often makes a comeback, even after apparently going away.

It’s appears as a green or brownish fine strand much like Hair Algae. The hairs are soft and slimy.

What Causes It?

There are a number of things that can set off Rhizoclonium Algae growth including lax maintenance, low CO2 and nutrients, and even poor water circulation.

How to Remove It?

Cleaning your tank is the first step towards eliminating these stubborn algae and adjusting nutrient dosing and CO2 levels.

I’ve had some success in clearing it after dosing my tank with EasyCarbo and Excel.

The Amano Shrimp will happily munch on it, so you can stock your tank with it too.

Some prefer starting a new tank completely than dealing with these algae, but I recommend testing the above methods first to see if you can avoid that.

13. Staghorn Algae

Staghorn Algae are easy to diagnose because their growth pattern resembles that of a stag’s horn, hence the name.

They belong to the group of red algae and they appear on aquarium decorations, the margins of plants, and technical equipment.

Immersing Staghorn Algae in alcohol will color it red.

Their physical removal is difficult, and no algae eater is going to munch on it, so removal can be a hassle.

What Causes It?

Lax tank maintenance is one of the main causes of most algae overgrowth, and Staghorn Algae is no exception. A disbalance of nutrients and low CO2 levels are some of the common culprits.

If you’re using a liquid fertilizer in your tank, the Staghorn Algae can appear as a result of an iron fertilizer overdose.

An improperly cycled tank in which ammonia is abundant can also kick-start the growth of Staghorn Algae.

How to Remove It?

As I mentioned, manually removing this alga is not easy, but you can give it a try and remove as much as you can with a toothbrush.

Next, you’ll need to up your aquarium maintenance game – perform regular water chances and test nutrients to create an environment in which aquatic plants can thrive and outcompete algae for resources.

As a last resort, you can try using a 1:20 bleach solution to sanitize hardy plants and other items. Be careful when reintroducing them to the tank, they should be bleach-free.

Unfortunately, common algae eaters find Staghorn Algae unappealing, so these are the only methods to get rid of it.

This concludes my presentation on the most common algae types and their causes.

Next, let’s see some algae prevention tips that can minimize the appearance or overgrowth of algae.

Tips to Prevent Algae Growth

Some algae are easier to remove than others and prevention is always better than dealing with an overgrowth of algae in your tank.

So, here’s what you should be careful about:

1.  Be Strict About Cleaning

Lax cleaning is a sure-fire way to promote algae blooms. Perform regular water changes (10-15% weekly) to remove excess waste that will feed your algae.

2.  Don’t Overfeed

Excess ammonia and phosphate resulting from overfeeding your fish is another way that algae growth can be promoted, so be careful with the amount of food you give to your fish.

3.  Keep Plants

Fast-growing aquatic plants are a great way to keep algae under check, because they’re competing with them for resources.

4.  Check Your Water Source

If you’re going to use tap water, check for nitrates and phosphates that algae just love. Remove these ingredients from your tap water or use reverse osmosis water.

5.  Avoid Direct Sunlight

Make sure your tank is not in direct sunlight and doesn’t get more than 9 hours of sunlight per day.

Using LEDs with automatic timers is a good way to make sure that your tank gets just the right amount of light.

Too much, too little light, or the wrong intensity can result in algae outcompeting your plants.

6.  Add Algae Eaters

While not all algae can be kept under control with algae eaters (We’re looking at you Staghorn Algae!), most algae can be prevented by stocking your tank with algae eaters.

Bristlenose Plecos, Amano Shrimp, Black Mollies, Nerite Snails, Rosy Barbs, Florida Flag Fish, Sun Snails, Otocinclus are just some of the algae eaters that can be used with success in preventing and even removing algae.

I hope that you won’t have to deal with the stubborn algae types we’ve discussed in this article and I hope that by following these prevention tips, you won’t experience algae blooms.

However, if you do happen to run into issues, I hope you can successfully remove them with the various methods I presented in this guide.


Featured Image: https://www.flickr.com/photos/m-paroczi/9756257851/

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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