Black Beard Algae (BBA): Causes and Treatment

Black beard algae is a red alga of the genus Audouinella. It is linked to fluctuating CO2 and organic waste, and can be removed by spot treatment and improved stability.

Identification

Black beard algae (BBA) forms tightly packed clumps of very fine hairs, usually black or grey but sometimes reddish or brownish. It is a member of the red algae (Rhodophyta), most often identified as the genus Audouinella. The genus grows as small tufts of red, brown or black hairlike filaments on solid surfaces, and it is a particular nuisance in aquaria because most algae-eating animals avoid it.

Where it grows

BBA tends to colonise inert objects such as rocks and bogwood, and the edges of slow-growing plant leaves. It favours a combination of strong light and abundant mineral nutrients, including nitrate and phosphate, and is often found where water flow is uneven.

Causes

Fluctuating CO2 levels, the most commonly cited trigger in both injected and non-injected tanks.
High organic waste from overfeeding, dirty filters and decaying matter.
Strong or aging lighting; old fluorescent tubes over about 12 months can promote it.
Poor or uneven water circulation.

How to remove it

Spot-treat affected items by spraying with 3% hydrogen peroxide, letting it sit about 5 minutes, then rinsing before returning to the tank.
Remove and clean detachable hardscape; bleach can be used on decor, but rinse and dechlorinate thoroughly before reinstalling.
Cut away badly affected leaves that cannot be cleaned.
Stabilise CO2, improve flow, keep the filter clean and increase water changes.

Animals that help

Few animals eat established BBA, but Siamese algae eaters, Florida flagfish and amano shrimp are reported to graze on it and can assist control.

Prevention

Keep CO2 stable rather than swinging between high and low.
Maintain vigorous plant growth and floating plants to filter light.
Avoid overfeeding and keep organic waste low.
Replace aging light tubes and ensure even circulation.