Audouinella

Audouinella, also known as black algae,[1] is a widespread genus of red algae, found in marine and freshwater environments. It grows as small tufts of red, brown, or black hairlike filaments on any solid surface - most dramatically in freshwater on the edges of slow-growing leaves. Often tolerant of high levels of pollution, acidity, Audouinella thrives on dissolved phosphate and nitrates. It reproduces via spores.

Audouinella
Scientific classification
(unranked):	Archaeplastida
Division:	Rhodophyta
Class:	Florideophyceae
Order:	Acrochaetiales
Family:	Acrochaetiaceae
Genus:	Audouinella Bory de Saint-Vincent

The form known as "black brush algae" (or "black beard algae", BBA for short) is a particular nuisance in aquaria, as few fish, even those widely promoted as algivores, will eat it.[2] In natural ecosystems, this genus that infests aquariums is found in unpolluted lotic systems.

It has been tested for germination and new growth using NO₃ and PO₄ fertilizers and such results came out negative for a decade's worth of observations. It has been shown to be inducible by limiting and varying the CO₂ concentration in planted aquariums. While other possible inducement mechanisms may exists, this is the most consistent and has been shown in many test by aquarists.

Jean Baptiste Bory de Saint-Vincent named the species to honour Jean Victoire Audouin, his co-editor in the Dictionnaire Classique d'Histoire Naturelle.