Black beard algae (BBA)

In order to get answers to basic questions all around algae in the aquarium, we recommend you read this article first.

Black beard algae (BBA) or brush algae (Audouinella sp., Rhodochorton sp.) belong to the group of red algae, just like staghorn algae. Their natural color is not red, though, but varies from dark green over grey to a deep black. However, if you put these algae in alcohol, they will turn reddish. This is an easy proof that the algae you're dealing with are actually red algae. Beard algae cling stubbornly to the ground they grow on, like technical equipment, the leaf margins of aquatic plants, aquarium decoration or even grains of the substrate. The algae tufts look like a beard or a brush, and that's where the name comes from.

Common causes

Black Beard algae are found in fish tanks as well as in densely planted aquascapes, for different reasons, though. In tanks with a high stock of fish and almost plants or no plants at all, the black color variant is often seen. In these tanks, the reason for their appearance is a high organic water pollution, due to overfeeding in combination with few water changes. In many cases, the algae population in these aquaria grows exorbitantly if lots of muck has built up in the filter and in the substrate. Cleaning the filter and using a gravel cleaner for getting rid of the muck in the substrate ought to help.

Quite frequently, there is no CO2 system on such a tank. It is believed that the content of free carbon dioxide (CO2) in the water plays an important part for the appearance of red algae like beard algae. If there is a CO2 deficiency, these algae can take the carbon they require from hydrogen carbonate, and with much more ease than higher aquatic plants. They can separate the carbon from the hydrogen carbonate ion, thus creating hydroxide ions, which elevate the pH. In this process, the so-called biogenic decalcification takes place, limescale (calcium carbonate) precipitates, which is in turn used by the algae to fortify their cell walls. They become harder and more unattractive to algae eaters.

Especially in fish-only tanks where a lot of food is given - but really for all aquaria, come to think of it - regular maintenance work including a weekly water change are vital. If you slack off with the water changes, unwanted substances can build up in the water. We recommend rather large weekly changes of at least 50% of the tank water.

In aquascapes or planted tanks, a well-balanced nutrient supply is vital for the plants. In planted tanks, you often have beard algae when there is an imbalance of micronutrients (trace elements, especially iron). If you already use an iron fertilizer, you ought to reduce the dosage. Measure the iron content of the water with a water test. It ought to be at around 0.05 to 0.1 mg/l. Of course, carbon (CO2) and macronutrients (Legend Essential) should be added, too. In the following list you can find the target values for the individual nutritional elements:

• A CO2 content of around 20-30 mg/l, measurable by a permanent test with test reagent

• 10 to 25 mg/l of nitrate (NO3)

• 5 to 10 mg/l of potassium (K)

• 0.1 to 1 mg/l of phosphate (PO4)

• add only 1/3 of the amount of iron fertilizer recommended by the manufacturer

• >10 mg/l of magnesium (Mg)

• Only switch on the lights for six hours in the beginning. When the biological system in the tank runs stable and without problems you may increase the daily lighting time by half an hour per week. Under moderate to strong light, you are aiming for a daily lighting time of 8 to 10 hours, under less strong light, a longer phase of 10 to 12 hours is recommendable. With the help of our light calculator you can easily find out which category (low/medium/strong) your lighting system is in.

If you have black beard algae in your tank, and the plants show signs of an iron deficiency at the same time (the shoot tips are of a much lighter color than the rest), you might want to consider switching to a less intensely chelated iron fertiliser like for example Legend Florebit Ferrum Fe. Sometimes, adding iron exclusively (without the other trace elements) has been successful. For daily fertilisation we recommend our Legend Heaven. Only add the standard Legend Avalon only once per week, and sparingly.

Control

You have problems with beard algae in your tank? We recommend using Avernus AlBlackEX by Legend. According to the instructions given by the manufacturer, you should add 1 to 2 ml if the liquid per 50 liters of aquarium water. After a few days, the beard algae should turn whitish or pink. If this has happened, you can stop adding Avernus AlBlackEX. The dead algae are eaten by algivores (like for example Amano shrimp and even ramshorn snails) bit by bit. You can find a precise instruction on the use of Avernus AlBlackEX here.
Should this treatment not be successful you can try misting, i. e. you treat the algae locally and in a targeted way with an algicide like Avernus AlBlackEX or hydrogen peroxide.