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Tips on how to get rid of black beard algae in aquarium

Is your aquarium having black fuzzy growths attaching on plants, décor end even substrate? Or has it already taken over your tank assuming beard like form? Is scrubbing it off not helpful?  Well, maybe it’s time you learnt how to get rid of that black beard algae in your aquarium.

What is Black beard algae?

Black beard algae (BBA) also known as Black Brush algae, is from the family of red algae. It’s one among most common algae types. It is generally considered a saltwater alga. That said however, some of its strains also thrive in freshwater.

In ideal conditions, it can reach 2 inches length in a scary short time.

Honestly, you are better off preventing it from “setting foot” in your tank. Working on how to get rid of black beard algae in the aquarium can be a herculean task.

The hardiness and stubbornness of brush algae makes it perhaps the worst algae to confront an aquarist. In-fact, in the face of it, some have opted to start a new tank altogether.

However, removing it permanently is possible. That is by using the correct approach and going for the “roots”.

How to identify it:

Because of the phycobilins (its water soluble pigments), it has a uniquely bold color range (of dark green-brownish/greyish-deep black). 

Black/greyish spots on aquarium’s surfaces and its contents, say substrate, plant edges, décor et al signifies its presence. This is however in its formative stages.

How to get rid of black beard algae in aquarium

It starts off just like a beard does; tiny spots. Unfortunately, if growth is not stopped, it grows into thick, slippery, furry and soft hair-like patches. It will literally own the whole space.

Being algae, it feeds on nutrients in the aquarium waters. That explains why it grows practically on any part of the tank.

Reproduction of black beard algae is both sexual and asexual. This is the norm in the red algae species. In the sexual method, gametes are produced for fertilization. On the other hand, it’s through cell division and fragmentation.


You can easily mistake for staghorn algae. It’s an all too common thing. Well, when fully grown, unlike the BBA, staghorn algae has more of a wiry beard look. Black brush algae on the other hand is more of a dense and thick cluster of bristles. 

What causes black algae in fish tank?

This black mold in your fish tank requires conducive and enabling conditions to take root. It is the same case in heavily planted aquascapes too.

Unfortunately, your input “mostly unknowingly” greatly aids its occurrence and spread. Read on for explanation how.

More than half the time, black beard algae causes are externally sourced.  This is via contaminated additions to the tank. They could be say plants, substrate and decors.

However, Carbon dioxide and light are the greatest (among others) enabling causes of growth;

Carbon Dioxide (CO2) deficiency and/or fluctuations in the tank:

BBA will grow in aquariums with low levels of CO2; say at about 10-15ppm. This is according to Barr Report.  The same is true in ecosystems with poor water circulation.

That however is not the case in water with higher CO2 levels.

Scientifically, unlike aquatic plants, red algae easily takes carbon from the hydrogen carbonate. Therefore, BBA is capable of splitting the hydrogen carbonate ion. This gives rise to the hydroxide ions.

The ions therefrom raise the water’s pH. Subsequently, biogenic decalcification happens. The resultant calcium carbonate fortifies BBA’s cell walls.

This causes the brush algae to harden. As a result, it becomes undesirable even to algae eating fish and critters. 

That explains how it takes over every breadth of the tank’s surface.

Further, low or fluctuating CO2 causes aquatic plants stress. Subsequently, this lowers their health and growth. Unhealthy plants are unable to resist BBA.

I trust you now appreciate how critical sufficiency and stability of CO2 is.

A CO2 canister can help you rescue the situation by adding CO2 to sufficient levels.

In addition, large water change can impact CO2 level just like a low running CO2 canister. Subsequently, this too will enable a thriving ecosystem for BBA. This is especially so with a planted tank.

However, you can reverse that by dosing the aquarium waters with a liquid carbon additive like seachem flourish excel.

Excessive light

Light is a great catalyst for black beard algae spread.

Aquarium light not only beautifies the tank and nourishes the aquatic plants but also feeds BBA. Having the light on round the clock is especially a good recipe for its growth.

Well, remembering to always switching off the aquarium LED light can be a challenge. However, automatic on and off switching can be eased if you use an aquarium timer.

You may be asking, is black beard algae harmful to plants? The correct answer is YES! Well, the effect of black spot algae on aquarium plants can be catastrophic.

If its growth is not stopped, it fills up the tank. This eventually covers the aquarium plants.

As a result, they are shielded from receiving the light they need for photosynthesis.

Besides, black brush algae will out-compete these plants for nutrients. Eventually, both planted and/or floating aquarium plants will not thrive. 


Overfeeding fish results in fast waste and detritus accumulation in the tank. These are good nutrients for BBA to thrive off.

Now, if the tank has low CO2 which makes photosynthesis difficult for aquatic plants, the nutrients are then left for the algae to feed on. This will lead to it explosion in the tank rapidly.

Phosphates from fertilizers added for the plants too become fodder for the algae.

Is black beard algae harmful to fish?

BBA is neither toxic nor poisonous and will certainly not harm your fish; at-least not directly. Infact, fish will particularly enjoy swimming and hiding in the new environment.

However, that enjoyment is not long-lived.

First, that black fuzzy algae in the fish tank is hardened. It’s thus undesirable for feeding even by natural algae eating fish. Therefore, part of the diet of fish is “off the table”.

Besides causing nutrients imbalance in the tank, as it spreads, it rapidly out-competes the aquarium plants for nutrients. This will lead to eventual death of the plants.

As a result, oxygen in the tank reduces and fish suffocation is imminent.

Besides, lack of oxygen is especially a destabilizer of the tank’s ecosystem.  All these factors subsequently makes the tank unsafe for the fish.

How to get rid of black beard algae in aquarium:

To start with, you won’t wish away this algae to its extinction. NO!!

How to get rid of black beard algae successfully is by first correctly knowing its cause. That is what you then fix.

Below are some tried and proven black beard algae removal methods you can apply:

Carbon boost in the tank:

This is particularly great with planted tanks.

We have clearly identified low carbon level or carbon level fluctuations as a high enabler of BBA growth. If it is the cause then, you need to focus your interventions to that.

While it won’t remove algae instantaneously, it however will halt growth and spread gradually. It’s akin to applying a chock hold till the algae is extinct.

With adequate water flow rate, this black beard algae remover will have a round the tank reach. Ensure to add the recommended dosage. This should be dependent on the tank size as well as the size of your pet fish stock.

However, you may also inquire of possible safe “overdosing” level incase results are slow to come by.

If you safely do it, you’ll notice changes with BBA turning red as it dies off. In addition, your other aquarium plants will start to get back their life. With this, the plants will reduce the nutrients available to the bba algae.

This you can do either with liquid carbon or using CO2 injectors. For CO2 injectors, you need a pressurized CO2 cylinder.

Caution however is that; add as advised lest you eliminate oxygen from the tank. This would subsequently suffocate the fish.

Using Hydrogen peroxide (H2O2) bath:

Treating black beard algae with hydrogen peroxide is easy even for rookies. First, this is an over the counter chemical product easy to find in the pet store near you.

If it’s not the whole tank that’s affected, you can then use hydrogen peroxide to clean aquarium decorations and plants.

For effectiveness, soak them in undiluted black beard algae hydrogen peroxide (specifically 3%) for 3 – 4 minutes. Thereafter, do a good freshwater rinse.

However, in some instances, it may not be practical to remove all the affected pieces in the tank. Therefore, isolation for cleaning and treatment won’t make much sense. The only option therefore is to treat the whole aquarium.  

In that case therefore, the only option is directly adding hydrogen peroxide to the tank.

The correct measure is added with a focus on area with a good flow rate. You should expect to get successfully rid of black beard algae from the aquarium if you do this once daily for 3 – 4 days.

Incase the desired results aren’t visible after say a week; you may consider repeating the process again. This time with “higher but safe dosage”.

Don’t be too worried of you tank inhabitants. They are safe, safe for the plants that may slightly fade. They’ll however soon recover.

Cutting of the light:

In identifying what causes black algae in fish tank, too much light is among the contributing factors.  Therefore, denying bba algae light will definitely eliminate it.

This may however be detrimental to those plants requiring too much of it. The good thing is they’ll soon come around.

To blackout the tank, use a thick blanket for cover for about 3 – 4 days. Prior to this however, you’d consider doing the following:

  • Feed your fish normal portions as you would normally,
  • Consider adding an air pump for oxygen increment. In addition, CO2 should be turned off,
  • Turn off the aquarium light,

Let the tank be in the dark for the aforementioned period.

After the said days, partially uncover the tank for about 45minutes. It allows your pet fish to adjust and adapt. Thereafter, fully uncover it and but only switch on the light after an hour.

By this time, the black fuzzy algae will have started to die off if not dead already.

At this point, tank equipment cleaning is recommended lest the dead algae clogs the tank. Thereafter, do a good water change.

Lower phosphate in the fish tank:

Another effective way on how to get rid of black hair algae is reducing phosphates in the tank. Remember nutrients in the water actively fuel BBA’s growth and spread.

Decay of any matter in the aquarium has phosphate as a byproduct.

It’ll also build up in the tank from pH buffers and aquarium salts.  That’s besides from use of carbon filter media.

Perhaps the most common source of phosphates in aquariums is tap water. It’s majorly used by most city authorities as a neutralizer of lead in water.

You can use a phosphate test kit to ensure not more than 0.25 ppm. Beyond that, it’s good enough for black brush algae to thrive.

Always use distilled water for any change to avoid surprise occurrences.

Having done all that, you still can use a phosphate (PO4) absorbing media. This will remove any remnant traces.

In addition, if the levels are within the safe zones, you can consider adding floating aquatic plants. They are effective in particularly taking in nutrients in the water.

Also very critical is reviewing your foods to those with less phosphate elements. That’s besides limiting the feeding portions.

Remember excess uneaten foods will decay at the bottom adding PO4 in the water column.

Add fish that eat black beard algae:

One of the common questions with regard to this is, “do shrimp eat black beard algae?” Well, as earlier noted, BBA caused by low CO2 hardens making it uninteresting even to fish that eat algae. However, if you choose to use black algae eating fish, inject CO2 to weaken and tenderize it. This will interest the fish and subsequently help you get rid of Black beard algae from the aquarium.

True Siamese algae eaters (SEAs) will love it.

Bristlenose pleco, Common goldfish, black molly, Chinese algae eater are some of the fish that eat black algae.

Trimming off the affected parts manually:

This is only effective at the early signs stage of bba in the tank. If you notice it on aquarium plant’s leaves, just pluck off the whole leaf.

However, this is very superficial. Many others cells are all over the water column just waiting to show.

What you see on the leaves is a call for deceive action.

Finally a caution; do not scrub or pick at brush black algae. This will just increase its chances of spread as the pieces float about in the tank. They’ll eventually settle at other parts of the fish tank.

Final word:

Kindly don’t let it take root in your tank. That is even if you think you know how to get rid of black beard algae in aquarium.

It’s without a doubt one of the most difficult algae to remove.

Algae is however just a visual indicator of something amiss in the tank.

Find out what it is and fix it before you are painfully contemplating or forced to build a new tank altogether.

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