Causes And Treatment For Black Beard Algae In Your Aquarium

Black beard algae (BBA), also referred to by the name black brush algae, typically grows on the edges of plants like Anubias and Java Fern, which are found in aquariums with lower ammonia levels.

They also like to grow on driftwood, substrate, aquarium equipment, walls, and decor. They are pretty tenacious, unsightly, and tough to get rid of once they permeate the aquarium. Black beard algae, as the name indicates, are usually black. But they can also vary in colors like dark green, brownish, grey, or reddish. They grow in dense, bushy clumps that are rooted in one place.


When you kill them, they turn into a red/pink color as they die and finally become white. Interestingly, despite their name, black beard algae actually belong to the red algae family. To easily confirm that you are dealing with BBA, put them in alcohol and they will turn reddish.

What Causes Black Beard Algae?

Black beard algae appear when there is an imbalance in your aquarium. These imbalances can create a favorable environment for the BBA to thrive. One day you have a great-looking tank. The next day, you notice things have gone south.

Common Causes

●      CO2 Fluctuations

Unstable and low CO2 (carbon dioxide) levels are the number one cause of black beard algae. If there is a CO2 deficiency, black beard algae can elevate the pH in the aquarium by taking the carbon that they require from hydrogen carbonate. The separation of carbon from the hydrogen carbonate ion creates hydrogen ions which cause the elevation of pH. They do this more easily than plants that have leaves and stems.

Without carbon dioxide, live plants can’t carry out photosynthesis. So live plants die while black beard algae thrive in an environment with low CO2 levels and/or poor water circulation.

●      Organic Water Pollution

The black color variant is often seen in tanks with a high stock of fish and few or almost no plants at all. These tanks experience high organic water pollution, which leads to the appearance of black beard algae. In addition, a combination of overfeeding with few water changes is a significant contributing factor.

Very often, if a lot of muck builds up in the filter and substrate, the algae population in these aquariums explode. Getting rid of the muck in the substrate with a gravel cleaner is helpful, and the filter should also be kept clean to keep the organic pollution at bay.

●      Water Changes

Regular water changes are a vital part of maintenance work, more so in fish-only aquariums where a lot of feeding occurs. To prevent unwanted substances from building up in the water, weekly 50% water changes work well since they prevent nutrient peaking. Many aquarists, however, prefer to do 25% water changes under normal conditions. So, to prevent the growth of black beard algae, regularly change the water. Not doing so will allow them to thrive.

●      Nutritional Imbalances

BBA can establish themselves when there is an imbalance of micronutrients like iron and trace elements. Nutritional imbalances often lead to nutrient peaks that can upset the water balance.

Signs of an iron deficiency in a planted tank with BBA are easy to spot since the tips of plant shoots appear much lighter in color from the rest of the plant. To remedy this situation, you should add the standard iron fertilizer with trace elements. Do so sparingly, not more than once a week.

●      Too Much Light

Black beard algae, like most plants, thrive in the presence of plenty of light. The more light it is exposed to, the quicker it will take hold and spread. If you leave your tank lights on for long periods of time, the more the algae will grow. Exposing the aquarium to sunlight makes the situation worse.

Reducing the amount of time that light shines on your aquarium is one way to stop the algae from growing out of control. To avoid the hassle of remembering to turn off your lights, you can use a reliable aquarium timer to do the job automatically.

How To Remove Black Beard Algae


The most effective and simple method for infected plants is to remove their infected leaves using aqua scissors.

Clean The Decorations

This calls for some elbow grease. You can clean BBA by scrubbing decorations in the tank using an old toothbrush. Using a siphon, you can dislodge any algae and other waste. Ensure it doesn’t float away to other sections of the tank. A razor blade can scrape algae that attach to the glass too.

Paint Over The Algae

You can lower the water level to where the growing algae are exposed to air. Measure the daily dose of liquid carbon, and using a paintbrush, proceed to paint undiluted liquid carbon onto areas with a lot of algae coverage. Leave the section exposed for a while before refilling the tank the same way you would during your weekly water change routine. Two days later, the black beard algae will turn reddish and die off.

Add Algae Eaters To Your Tank

Adding algae eaters to your tank is a natural way to control BBA. Among the few fish that feed on black beard algae are the Siamese Algae Eaters (crossocheilus siamensis) and Florida Flag fish.

Shrimp and snails also feed on algae, although they usually don’t eat enough daily to make an impact.

Boost CO2 Levels

By adding liquid carbon to the water every day, you maintain an aquarium environment that does not attract BBA and is healthy for the inhabitants.

Improve Water Quality

Carrying out weekly 25% new water changes is vital in your maintenance regimen. Clean the filter in the aquarium water monthly to remove muck and clogging. You can also change it whenever necessary. Aquarium substrates need vacuuming every week to remove waste, decaying fish food, and other detritus.

Regularly monitor pH to keep the water within fish/animal-friendly parameters.


Having to deal with stubborn, unsightly, black beard algae is so much trouble and can be best avoided by good, regular maintenance. Sterilize all new plants and quarantine new fish before you introduce them into your aquarium to offset black beard algae growth.

John Brandon

John has kept fish all his life (since he was about 5). He started with keeping guppies and fell in love with fish keeping almost straight away. That was 40 odd years ago. These days John still keeps fish and currently has two large tanks where he keeps many different types of fish such as Angelfish, Neon Tetras, Goldfish, Guppies and many more.