Brown Hair Algae in Freshwater Aquarium – Causes and Treatment

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Nobody wants to see algae in their fish tank. Although these microorganisms aren’t dangerous directly, their presence will eventually disrupt the environment’s esthetics and even affect the plants and the fish. Plants are especially in danger if the algae cover them and restrict their access to sunlight.

Today, we will discuss the infamous brown hair algae and why its presence speaks volumes about the health of the environment.

What Causes Brown Hair Algae in Aquarium?

The main cause of an excess of Brown Hair algae is silica. For a clearer understanding of the situation, let’s assess the 2 main terms here: silica and the algae themselves. First, Brown Hair algae aren’t algae in the true sense of the word. They are rather cellular organisms, similar to bacteria, called diatoms. These can exist both solo and in groups and can spread through the entire environment if the conditions are optimal.

The thing that makes diatoms so effective and resilient is their ability to use silica to create protective shells around them. Silica exists pretty much in any aquatic habitat and is the result of oxygen and silicon mixing together. You can find silica in glass, quartz, sandstone, volcanic rock, sand, etc.

So, it’s safe to say that all aquatic environments have enough silica to promote a ‘healthy’ Brown Hair algae development which you need to address. But this isn’t the only factor linked to the algae’s emergence and spread.

Brown Hair algae will also appear in the aquarium for a variety of other reasons, such as:

  • Intense lighting – Algae tend to bloom in intense lighting, spreading and expanding throughout the entire environment if left unchecked. The interesting part here is that neither do fish nor plants require too much lighting, intensity-wise. Most aquarists light up their tanks excessively for aesthetic reasons rather than to fulfill their fish or plants’ needs.
  • Excess nitrates – Nitrates are the second-hand result of decaying matter in a cycled environment. For a clearer picture, you first have ammonia and nitrites as the direct products of fish waste, decaying fish food, and animal and plant matter rotting in the water. Then you have nitrifying bacteria converting those dangerous chemicals into nitrates, which aren’t as harmful to your fish and plants. The algae will use those nitrates as a food source, among other nutrients, allowing them to bloom fast.
  • Low water quality – Lack of maintenance and rare water changes can contribute to algae development due to decreasing overall water quality.

The problems with having Brown Hair algae in your tank go beyond the aesthetic. Sure, the algae will foul the water and look ugly, destroying the environment’s aesthetic factor, but the problems go beyond that. If left unchecked, Brown Hair algae will cover the plants, limiting their access to sunlight and inhibiting their ability to perform photosynthesis.

As a result, the plants will begin to starve and die, unable to support their physiological processes. As a result of plants dying, the oxygen levels in the water will drop, which will affect the fish directly. To prevent this vicious circle, consider taking immediate measures to limit the spread of Brown Hair algae and even removing them completely.

How to Get Rid of Brown Hair Algae in Aquarium?

There are several ways to remove Brown Hair algae from the tank:

– Remove Them Manually

Brown Hair algae are fairly easy to remove since they aren’t as rigid and compact as other algae species. While Brown Hair algae can grow on any surface and create compact patches wherever they can, they also float freely into the water. This is what causes the tank water to look muddy and dirty and the reason why Brown Hair algae are so hated.

However, that’s also the algae’s main weakness. That’s because a good filtration system will eliminate the floating algae quite easily. So, all you need to do is clean the tank’s surfaces with a sponge or a rag and allow the filter to suck in the floating algae. You should also remove the algae from the plants’ leaves and stem with care not to damage the plants.

If the infection is too spread out, consider performing water changes to eliminate the excess algae faster. The filtration system will do the rest.

– Bring in Algae Eaters

This is another popular option, especially thanks to being a natural method of containing the algae’s spread. No chemicals involved and only minimal efforts on your part. A variety of aquatic creatures will consume these algae, including Amano shrimp, nerite snails, or Otocinclus catfish, to name a few.

The problem here is that not all these species are compatible with each other. They are also not compatible with a variety of other fish species. So, you might have difficulties finding reliable tankmates for them if you’re looking to create a community setup. To prevent any problems, you should assess each species’ water requirements to make sure they can cohabitate.

And, even more importantly, don’t rely on algae eaters to keep the algae population in check. You should also consider other treatment modalities and prevention strategies to achieve the best results.

– Perform Water Changes Wisely

This section refers to 2 primary aspects:

  1. The frequency of the water changes – At least once per week, depending on your tank’s requirements. As a general rule, smaller tanks require more frequent water changes since ammonia and nitrites build up faster in those. You also need more frequent water changes in overstocked tanks or when housing messy fish like cichlids or goldfish.
  2. The water to use – I advise avoiding tap water, even after having been dechlorinated. Tap water contains a lot of phosphates and nitrates which may cause an excess of these nutrients in the water, causing the algae will bloom. Instead, use RO (Reverse Osmosis) and distilled water since these are very low in chemicals and are safer.

The idea with water changes is to:

  • Limit the amount of nutrients in the water to prevent excesses
  • Oxygenate the environment better
  • Remove debris, dirt, fish waste, and food residues that could support algae bloom
  • Dilute ammonia, nitrites, and other dangerous chemicals that could affect the tank’s flora and fauna

However, be careful how you perform your water changes. Too frequent or too massive water changes (in excess of 25%) could actually cause problems rather than fix them. Excessive water changes will not only remove too much of the water nutrients but will also imbalance the tank’s biofilm.

This consists of beneficial bacteria that consume ammonia and contribute to the system’s chemical and biological balance. And you don’t want that balance disturbed.

How to Prevent Brown Hair Algae in Aquarium?

Prevention is obviously a lot more important than treatment since algae, in general, are more difficult to remove when mature. I would say that the prevention process encompasses 3 fundamental strategies:

– Algae Grazers

We’ve already discussed this point, but it’s worth reinforcing it. Many aquarists, especially novices, tend to choose their fish species of choice based on looks. They will simply choose the ones that appeal to them the most and draw the line under them. I say you should also consider a species’ usefulness, not only its looks.

Algae grazers may not be as exhilarating as other fish, but their presence is key in any closed aquatic environment. Fish like plecos, otocinclus, and suckermouth fish may not be too handsome or exhilarating, but they’re undeniably useful. They will constantly look for algae to graze off of rocks, tank walls, substrate, and other hard surfaces around their environment.

Algae eaters may not be able to eradicate the problem on their own. But they will contain the algae’s spread long enough for you to take additional measures.

– Consistent Tank Maintenance

I would say that this is the golden bullet of algae prevention. Simply put, keeping your tank in mint condition will prevent algae bloom and keep the environment stable and healthy. You can achieve this via several wise and welcome strategies:

  • Daily tank cleaning – This may sound like a chore, but it’s not. It will take no more than 5 minutes of your time each day if that. In short, you should remove any excess fish waste and food leftovers sinking on the substrate after each meal. Since most fish require around 2-3 meals per day at most, you won’t have that much work to do.
  • Plant care – This is a rarely discussed subject but one of the utmost importance. Aquarium plants aren’t objects, they are living beings. So, they need their fair share of care and maintenance to remain healthy, which is key for a stable environment. Healthy and strong plants will oxygenate the environment and consume ammonia and CO2, both of which will benefit the fish. You should provide the plants with adequate nutrients, a nutritious substrate, and ideal water conditions to thrive.
  • Stable water change routine – Water changes are necessary in any aquatic setup, no matter how large, the type of fish you’re housing, or how many plants it contains. On average, you should change around 15-20-25% of the water, depending how large the tank is and how dirty it gets. Some fish species require more frequent water changes, while others not so much.

Aside from these measures, you should also have a reliable filtration system to cleanse the water of toxins and prevent the ammonia buildup.

– Permanent Algae Control and Removal

The real problem here is that the Brown Hair algae are extremely resilient and adaptable. No prevention method is 100% effective against these types of algae. If the conditions are right, the algae will appear. The only thing you can do is minimize the algae’s impact and take away their means of survival.

In this sense, you should always monitor and assess your system’s health indicators, no matter what prevention methods you have in place. Verify your aquarium visually every day, if possible, to detect the Brown Hair algae and address them in time.

Is Brown Hair Algae Bad for Fish?

Brown Hair algae won’t harm your fish directly, but they might do so indirectly. That usually happens due to the algae’s ability to take over the environment and change its parameters. Simply put, the algae will impact their environment once they spread out of control.

To prevent that, you should take measures to contain the algae’s spread. Refer to all of the points I’ve already mentioned in terms of prevention and treatment.

Will Brown Hair Algae Go Away?

Yes, Brown Hair algae will go away, but not by themselves. Algae will take over their environment and will ‘take it into the ground’ to put it like that. That is if you allow them to. In short, Brown Hair algae will spread uncontrollably if the conditions are right and will not go away on their own.

So, if you notice Brown Hair algae in your tank, be prepared to intervene. Ignoring the algae will only make things worse.

Do Fish Eat Brown Hair Algae?

Yes, a variety of fish eat Brown Hair Algae. Here, we include both freshwater and saltwater fish, along with snails and various shrimp species. Some good species to consider for your tank include:

The list is vastly larger, encompassing both specialized algae eaters and general omnivorous animals that eat algae occasionally. I would say that algae eaters need to exist in every tank, provided you have the right conditions for them. And this is the catch.

You need to make sure that the algae eaters can coexist with the fish you’re actually aiming for. In many cases, different fish species display different environmental requirements in terms of temperature, pH, space, tank layout, etc.


Brown Hair algae will grow if the right conditions are met. The existence of silica in the environment is the clearest predictor of Brown Hair algae. Fortunately, these algae are not harmful when kept under control.

Even more, fortunately, you now have a dos-and-don’ts list to refer to when dealing with any algae-related problems. You’re welcome!

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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