How to get rid of Black Beard Algae (BBA)

The term Black Beard Algae (BBA) refers to algae from the genera Audouinella, which contains many sub-species. Audouinella species occur in both marine and freshwater. These algae appear as short reddish or black turfs of hair. They grow in small bunches and first appear as small furry black dots as small as the tip of a pen. They are often found on the edges of older leaves of plants, or on hardscape and filter outlets. Some species can grow to more than a centimeter in length.

Why does BBA attach especially readily to plant leaf edges?

Plants may look still and unmoving on the outside, but there is complex biochemistry going on inside the plant as it generates carbohydrates, sugars and other metabolites from photosynthesis.

Plants are leaky organisms and aquatic plants eject a portion of excess metabolites directly through their leaf surfaces and margins. Algae feed off these waste organics.

Plants under stress, such as when adapting to a new environment, require a significant amount of re-programming of proteins and enzymes. This results in increased excretion of waste proteins and metabolites. This makes them particularly vulnerable to algae. Conversely, when plants are healthy, they generate defensive antimicrobial chemicals and enzymes to ward off pathogens and algae.

Stressed/unhealthy plants attract algae, while healthy plants are very resistant to it.Older leaves leak more organics, and plants defend older leaves less as they are less valuable. This is why in most tanks, you see algae attaching only to some plants but not others, and most commonly to older leaves first.

Plant stress is caused by many factors. Recently transplanted plants inevitably face some adaptation stress as they adjust to the new environment. Insufficient CO2 or nutrient levels will cause poor growth. Frequent movement of plants and large changes to the tank environment can cause stress as they try to adapt to these changes.

A tank with a lot of old, deteriorating leaves on the plants is especially conducive to algae. A tank with dominant plant mass and robust, fresh-leafed plants is not. This means that plant husbandry plays a big role in managing algae. Regularly cutting off old leaves to make space for new growth and replanting healthy tops/discarding old, deteriorating bottoms are key to maximising the growth of new, fresh leaves.

The approach of rejuvenating growth to avoid algae applies to BBA, but it is a universal concept that can be applied to manage all algae.

Black beard algae

High levels of organic waste & detritus in the planted tank encourages BBA to spawn. If they are found attached to plants, it is most commonly caused by stress induced by fluctuating CO2 levels. In tanks where plants are healthy, but there a high level of organic waste in the tank environment, BBA will be found attached to hardscape instead. 

If it is found on rocks or driftwood, it is almost always found in areas of fast flow in the path of CO2. Often this is due to aquarists who are obsessed with excessive flow. It's often found on filter outlets and on CO2 diffusers - which are often placed in the path of high flow. In such tanks, slowing down the flow or redirecting it to create a more even flow distribution will have a big impact.

Barr report suggests that BBA strives when CO2 is present but at low levels; between 10-15ppm. Non injected tanks (low tech tanks) and tanks with higher levels of CO2 are less vulnerable - to this end, it seems to occur most often in tanks where CO2 injection is used but optimized poorly.

BBA has little connection to nutrient levels or light spectrum. Both tanks with very lean water column fertilization and rich water column fertilization are vulnerable to it. It has very strong correlation to organic waste levels, plant husbandry and CO2 fluctuations.

American flagfish, mollies and SAE (Siamese algae eater) pick at it when there are no tasty alternatives. However, they are seldom adequate solutions.

What causes black beard algae in planted tanks?

• Fluctuating CO2 levels in the tank.
• High amount of organic waste/dirty tank.
• Stressed plants/old growth.
• Instabilities that lead to plant stress; poor water quality, harsh use of biocides etc
• Excessive flow with heavy misting (observe if BBA spawns in areas that are directly in path of flow), especially on slow growers/moss/hardscape.

How to get rid of blackbeard algae?

• Spot dose APT Fix directly onto BBA at first appearance to prevent spreading. It is highly effective against BBA. 
• Pruning and replanting of healthy tops, cut away and discard old growth.
• Find ways to even out excessive flow. In many tanks, slowing down flow alone can prevent BBA from triggering.
• Find ways to stabilize CO2 levels.  Generally speaking, higher injection rates create more stable CO2 levels, so increasing CO2 injection is generally recommended.
• Regularly vacuum substrate surface while stirring up debris with turkey baster (see below) to reduce organic debris - this makes a big impact.

To learn more optimising CO2 gaseous exchange and flow patterns, read here.