How to Remove Black Beard Algae from the Aquarium

Black Beard Algae
Black Beard Algae on an Anubias plant leaf

Black beard algae, hair algae or brush algae (Audouinella sp., Rhodochorton sp.) belong to the group of red algae – despite its classification, the black beard algae’s colour ranges from a dark green, browny gray to a deep black. It is the most difficult algae to get rid of – but there is now a very easy way !!!

Root cause of Black Beard Algae

The root cause of black beard algae is a lack of CO2 in the aquarium. This is often a result of too bigger water changes.

What conditions does Black Beard Algae thrive in ?

Black Beard algae is found in any kind of freshwater fish tank – both tropical or cold water. BBA occurs in densely planted aquascapes, in tanks with a high stock of fish. Tanks with only several plants or no plants at all are just a susceptible. It tends to do best in aquariums of low flow.

This algae does grow very fast in unstable setups. Fishkeepers that overfeed fish will only fuel algae growth (fish poo makes great fertilizer.) Also irregular water changes (eg resorting to massive water changes of 75-80% every 3-4 months instead of fortnightly one third) make for unstable CO2 levels. And aquariums either in direct sunlight or with a lighting system that is too bright or lights left on for too long are a main trigger for algae.

Does Black Beard Algae harm fish or plants ?

Black Beard Algae is not harmful to fish, in fact fish like to hide in it I find. However to plants it is damaging as it spreads and covers the plants leaves reducing photosynthesis eventually completely taking over.

Lifecycle of the Black Beard Algae

What starts out as “stubble” soon forms into a “3 day growth” before evolving into a complete hair – see diagrams below.

Removal of Black Beard Algae

Unknown to many there is a very easy way to quickly rid your tank within a week or two of this horrible imposter to your aquarium.


If there is a very high presence of black beard algae – ie the aquarium is significantly overgrown, then it is best to manually pull out what you can before starting anything. Just grab clumps and firmly pull them removing what you can.


After removing as much of the algae by hand we recommend you complete a 50% water change to your aquarium and clean all filters and media in the same aquarium water that you removed. (Never wash your filters under tap water as the chlorine kills all beneficial bacteria residing there!!)


Remove any carbon or bio chem zorb products from the filter.
Let everything settle for 24 hours.


The following day come and buy a product called Flourish Excel. The bottles come in 4 common sizes. Work out your literage of your aquarium by multiplying in centimeters the length x width x height then divide that number by 1000 and the result is your aquariums litre capacity. Subtract further any gravel, driftwood or rocks etc. The dosage and procedure is as follows:
1) Add 10ml of Flourish Excel per 40L of aquarium water.
2) Wait 48 Hours.
3) Repeat dose. (Add 10ml of Flourish Excel per 40L of aquarium water.)
4) Wait 48 Hours
5) Repeat dose. (Add 10ml of Flourish Excel per 40L of aquarium water.)
6) Wait 48 Hours
7) Complete a 50% water change – and if still present repeat steps 1 – 7

Please Note:

Sometimes it will take longer than a week to remove all of the Black Beard Algae, commonly it takes between 10 and 21 days to completely erradicate from an aquarium.

To prevent future outbreaks of Black Beard Algae, ensure you do not overfeed your fish (we recommend feeding your fish only what they can consume in 30 seconds – twice a day.)

Please note that invertebrates such as yabbies, shrimp and fish species such as Corydoras varieties do not like high dosages of the product and can fall victim to its presence.

Also note that if you accidently overdose the dosage of Flourish Excel to what is written above then immediately complete at least a 50% water change.

Disclaimer: The information provided here is of a general nature only. There are site specifc factors that are not addressed here that may also affect the health and well being of your fsh, as such Aquarium Fish Paradise will not be held liable for the performance of your fish.