Skip to Content

Brown Hair Algae 101: Causes, Removal Tips & More

Disclosure: When you purchase something through my affiliate links, I earn a small commission. As an Amazon Associate, I earn from qualifying purchases.

In my early days of fish keeping, I had no idea that there as so many kinds of algae. Learning about the different types made it easy to identify and control them. In this article, we will dive into the particular case of brown hair algae.

Brown hair algae belong to the Phaeophyta phylum and are characterized by filamentous strands resembling brown human hair. You typically find them in aquariums abundant with light, nitrate, and phosphate.

As we move forward, you will learn what causes brown hair algae and what steps you can take in order to get rid of them. I will also list some great hair algae eaters that will help you control the situation in your tank.

A picture of brown hair algae that have just started to grow on aquarium plants.

What Is Special About Brown Hair Algae?

Brown hair algae are filamentous. Robert G. Wetzel said in Limnology that brown filamentous algae appear primarily in marine environments.[1]

Although, he acknowledges that some species can thrive in freshwater. You find it on stable surfaces such as rocks and driftwood.

Identifying the genera and species of brown hair algae is easier said than done. 

John D. Wehr (Louis Calder Center, Fordham University) noted that studies about this organism are rare.[2] For that reason, brown hair algae are difficult to classify.

This is a problem because many consumers confuse red (Rhodophyta) hair algae for brown filamentous algae (Phaeophyta).

Like brown algae, red algae are rare in fresh water. In fact, only 5 percent of red algae manifest in freshwater aquariums.[3]

The organism tends to frequent saltwater environments. It is not uncommon for aquarists to perceive red algae as the organism’s brown counterpart.

Some people maintain a healthy population of red algae because the vibrant colors of the organism can improve the tank’s appearance. 

But anyone that favors this practice should apply caution. The last thing you want is for the red algae to run amok. 

Comparisons with red slime algae are not as common because brown hair alga has strands that resemble hair, while red slime alga looks like slime.

An image of aquarium fish using brown hair algae for shelter.

Additionally, red slime algae are cyanobacteria, not algae. Yours may take on blackish, green, blue-green, orange-yellow, deep purple, and reddish-brown colors.[4]

Conventional brown algae are a different case because they can pass for brown hair algae under the right conditions. 

But brown algae are diatoms that meet their energy requirements using photosynthesis. They will coat various surfaces like dust or snowflakes.[5] 

If you’re trying to determine whether your aquarium has brown hair algae or diatoms, you can rule out the diatoms by taking some algae from the water and rubbing them between your fingers. 

Brown diatoms will turn to mush, however, the same cannot be said for brown hair algae. 

Brown hair algae are not as complex as people think. They share many attributes with green hair algae, including a slimy texture and long hair strands.

Surprisingly, you can find green, red, and brown filamentous algae abundantly in the same settings in the wild.

If all that sounds confusing, here is a table that makes it more clear:

Brown hair algaePhaeophytaBrown filamentous strands
Red hair algaeRhodophytaRed strands resembling deer antlers
Red slime algaeNot algae (cyanobacteria)Reddish-brown/purple slimes
Brown algaeNot algae (diatoms)Heavily branched/cup-like stalks

Pro-tip: Here is an article where I explained everything there is to know about hair alga, including some detailed pictures on how to identify it and its different subtypes.

Are Brown Hair Algae Harmful?

Hair algae are neither toxic nor harmful to fish. They may entangle the creatures on occasion, but that’s about it.

Many aquarists remove the organism because brown hair algae are unsightly. However, they don’t pose a direct threat to your aquarium’s inhabitants.

What Causes Brown Hair Algae?

Brown hair algae respond to the same variables that attract most hair algae types, including:

1. Nitrates

As I previously discussed, algae thrive in areas with high nitrates. Nitrates appear when bacteria convert ammonia into nitrites and then nitrates. Every cycled tank has nitrifying bacteria. 

Additionally, ammonia is inevitable in aquariums because fish continuously generate waste that produces the substance when it rots. Therefore, you cannot prevent nitrates from forming. 

Fortunately, nitrates are harmless in small quantities. They only pose a threat when you permit their concentration to spike and exceed 40 to 50 ppm.

Besides harming fish, high nitrate levels will encourage algae growth. 

A paper in ‘Frontiers in Bioengineering and Biotechnology’ explored the efficacy of algae as a tool for managing nitrogenous waste, including nitrates.[6]

Algae do such an impressive job of consuming nitrates that some organizations use them to control high nitrate levels.

This tells you everything you need to know about algae’s relationship with nitrates. Brown hair algae will thrive in tanks with a high nitrate concentration.

This image demonstrates the filamentous shape and slimy texture of brown hair algae.

2. Phosphates

Phosphates occur naturally. They are common in aquariums, which is good because phosphates are necessary for plant growth. 

You can’t afford to eliminate them altogether. Doing so will stunt the growth of your tank’s foliage.

If the leaves are turning yellow or purple, you probably have a phosphate deficiency. Unfortunately, high phosphate levels encourage algae growth.

Like nitrates, the relationship between algae and phosphates is well documented. 

The University of Amsterdam performed a study to understand the response of marine algae to changing ocean conditions.[7]

During the investigation, they would manipulate the growth of algae by limiting access to phosphates.

This gives you an idea of the impact of high phosphate levels on brown hair algae growth. 

You need just enough phosphates to keep your plants happy but not so much that the algae bloom uncontrollably.  

3. Lighting

Do you know why aquarists are discouraged from keeping fish tanks next to windows?

Direct sunlight is dangerous, and not just because it raises the temperature. Excess light encourages hair algae to grow.

If you have too much light but the nutrients are unbalanced or insufficient, brown hair algae will cover every surface in the aquarium.

Magnification under a microscope beautifully demonstrates the filamentous structure of brown hair algae.

How Do I Get Rid Of Brown Hair Algae?

Brown hair algae are a menace. The challenges you will encounter while removing the organism depend on the severity of the infestation. These methods will work:

1. Mechanical Removal

You can remove the brown hair algae manually. Put some gloves on and pull the algae out of the water with your hands. 

You can’t do this with brown diatoms, as they will disintegrate into powder. But hair algae will maintain its shape and form.

If the organism is strong enough to entangle fish, you can pull it out of the aquarium without spreading it, especially if you shut the filters and pumps off beforehand. 

The gloves matter because your hands can add deadly chemicals and bacteria to the tank. 

Plants are somewhat complicated. You can try pulling the algae out of the foliage. But some infestations will force you to cut the leaves off. 

Cutting the entire plant defeats the purpose because aquarists remove algae to protect the plants. Some basic trimming should be enough.

2. Algae Eaters

Find creatures that eat hair algae. Some examples of efficient algae eaters include:

  • Amano shrimp
  • Mollies
  • Siamese algae eaters
  • Trochus snails
  • Turbo snails
  • Bristlenose plecos

Algae eaters are convenient because they don’t require direct supervision. So long as the conditions in the aquarium are conducive to their survival, you can leave them to their business.

A sizable population of shrimp and snails will keep the brown hair algae under control. Naturally, you shouldn’t crowd the tank with algae eaters. 

They will saturate the water with waste and leftovers, producing ammonia, nitrite, and nitrate spikes that encourage algae growth.

If your tank is too small to accommodate the number of algae eaters you need to eliminate brown hair algae, deploy additional algae removal methods. 

You don’t have to restrict yourself to one approach. For instance, you can remove as much hair algae as you can using your hands. The algae eaters will take care of the rest. 

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.

3. Water Change

Brown hair algae will multiply because of high nitrate and phosphate levels. Nitrate and phosphate levels spike because of uneaten food, fish waste, and rotting organisms in the water.

A water change solves this problem directly by removing the nitrate and phosphate concentration.

Heavy infestations require significant water changes, especially in neglected tanks. But you can also carry out smaller water changes daily until the conditions in the aquarium improve. 

Indirectly, the water change can fight algae by removing some of the waste that attracts nitrates before it can decompose.

4. Aquarium Maintenance 

Water changes cannot fight brown hair algae alone. The practice can remove some pollutants, but not all of them. You need a strong filter to catch debris. 

But even with decent filtration, some pollutants require manual removal, especially dead plants and animals. 

Put your gloves on and take these organisms out of the tank. You should also vacuum the substrate. Fish waste and leftovers usually sink to the bottom. 

Removing them through conventional means becomes impossible once they disappear into the gravel, which is why the vacuum is so important.

Siphoning the substrate is pretty easy and affordable these days. To do that, I got the Laifoo Aquarium Siphon Vacuum Cleaner (link to Amazon).

Using this product twice a week will get rid of a huge amount of debris and leftovers. If you’ve never done this before, here is a great video that will walk you through it:

5. Lighting

Maintain a regular day/night cycle. You cannot fight brown hair algae by removing artificial lights. 

Dim lighting encourages the growth of brown diatoms, and plants absorb oxygen in the dark. Give the tank 8 to 12 hours of light and an equal amount of darkness. 

6. Water Conditioners

You can buy water conditioners that neutralize ammonia. Without ammonia, the nitrifying bacteria cannot make more nitrates. 

The one that I use is the well-known Seachem Prime Conditioner (link to Amazon). All you have to do is add 1 m/L for every 10 gallons of water.

Some people add nitrates to the tank via contaminated tap water. But you can prevent nitrate spikes by conditioning the tap water during a water change. 

If nitrate levels always rise after a water change, your water source is probably contaminated. 

Will Brown Hair Algae Go Away On Their Own?

Algae appear in new tanks because they have a nutrient imbalance. However, as conditions improve, the algae will disappear on their own.

That is especially true if you have creatures in the aquarium whose diet includes algae.

Small infestations of hair algae can also disappear in established tanks if you have a strict maintenance routine.

But substantial infestations in a poorly maintained tank cannot disappear without your direct involvement.

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


Brown hair algae are different from conventional brown algae. In fact, the latter isn’t actually algae, but diatoms.

Therefore, you can successfully pull out brown hair, while brown algae will disintegrate in your hands into a powder.

Brown hair algae usually thrive in areas enriched with light, nitrate, and phosphate. That is why maintaining a clean environment without toxins is essential when trying to control them.

One of the most important steps is vacuuming the gravel. This part usually contains a lot of debris that rots and turns into ammonia, and later on, nitrate.