How to get rid of Black Beard Algae (BBA)

The term Black Beard Algae (BBA) refers to algae of the genus Audouinella, which contains many subspecies. Audouinella species occur in both marine and freshwater. These algae appear as short reddish or black hair. They grow in small clusters and first appear as small furry black dots about the size of the tip of a pen. They are often found on the edges of older leaves of plants, or on hard surfaces and filter outlets. Some species can grow to over a centimetre in length.

Why does BBA attach especially readily to plant leaf edges?

When aquatic plants experience adaptive stress, they release some of the excess metabolites directly through their leaf surfaces and edges. This triggers algal spores to bloom and attach to the plant. Adaptation stress occurs when a plant is transferred to a new environment or when there are sudden changes in the current environment. It can also occur when the plant's growth requirements are not met and the plant struggles to survive. Healthy plants in a stable environment produce defence chemicals that prevent algae from attaching, while stressed or unhealthy plants release waste metabolites that trigger algae attachment.

Plants adapt their physiology to the current light, nutrient and water conditions. If we keep changing the tank parameters, the plants will be stressed trying to keep up with the new parameters. This is the main reason why unstable tank conditions lead to more algae spawning. This is also the main reason why newly planted aquariums have far more algae problems than a mature, established aquarium.

Fluctuating CO2 levels in aquariums are one of the biggest triggers for BBA to spawn, as plants have to make significant adaptations to their physiology to match the CO2 availability in their environment. This is one of the major triggers for BBA in CO2-injected aquariums.

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.

As plants grow, they concentrate their energy on new top growth - where light is plentiful and there is an opportunity to break through the water surface to reach previously gaseous CO2. Older leaves further down the stem are abandoned and these are often colonised by algae as they deteriorate. Regularly cutting off old leaves to make room for new growth and replanting healthy tops / discarding old, deteriorating bottoms are key measures to maximise the growth of new, fresh leaves. A tank filled with fresh growth is more resistant to algae.

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

Organic waste and detritus

High levels of organic waste in a tank combined with high light levels can cause BBA spores to bloom. In tanks where the plants are healthy but there is a high level of organic waste in the tank environment, BBA will be found on the substrate rather than on the plants.

In planted tanks, fish and shrimp faeces and old leaves break down into organic detritus on the substrate. Many hobbyists believe that this provides a source of nutrients for the plants. While this is partly true, the decomposition process is not clean and the remaining organic waste, combined with high light levels, causes algae to bloom.

We recommend skimming organic detritus from the substrate surface during weekly water changes. In high light tanks this will have a huge impact on whether or not BBA is triggered to spawn.

For plant species that are vulnerable to algae, doing large weekly water changes and siphoning off substrate detritus makes a huge impact. This is especially so for tanks that have slow growers and/or use high light.

BBA only in high flow areas?

BBA is commonly found in areas of high flow in the path of CO2. It is also commonly found on filter outlets and CO2 diffusers - which are often placed in the path of high flow. In such tanks, slowing down or redirecting the flow to create a more even flow distribution can help the situation. Existing BBA will still need to be treated with algicides, but a gentler water flow may reduce it's occurrence.

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

Fertilization and light with BBA

As with all algae, higher light levels cause more spores to bloom. However, BBA has little to do with nutrient levels or light spectrum. Tanks with both very low and high nutrient levels are susceptible to it, and whether or not you use high blue light has no effect on the rate at which it blooms.

The main triggers for BBA are organic waste levels, deteriorating plants and CO2 fluctuations.

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, Click here.