Compsopogon – Compsopogon, Black Beard Algae.
(Black Brush Algae, BBA, Black Beard Algae, Staghorn).
Several species of this genus are known: Compsopogon coerules, aeruginosus, lusitanicus, hookerii, iyengarii, indicus, chlybeus. It consists of long, slightly branched, rather thick and rigid filaments, semi-transparent, dark green to almost black in color. They feel slightly rough to the touch. The first and second species of Compsopogon can form solid carpet-like overgrowths, sometimes in a very short time (a day or two). It grows in tufts or black groups. Their dark green, almost black tassels appear everywhere: on the substrate, walls (carpet overgrowths), auxiliary devices, stems, and leaves of plants. They attach to leaves mainly at the edges, and especially willingly to sharp tips. Sometimes it grows in areas of the aquarium with fast water movement.
Compsopogon is very resilient in the struggle for survival. It is quite difficult to completely remove them from the base without damaging the leaf tissues, so deeply do they penetrate into plant tissues. It is capable of penetrating not only into plant tissues, but also firmly attaching to the substrate, walls, and aquarium equipment. At the same time, it is not a parasite, using other plants only as a substrate. However, by attaching to them, it destroys tissues and, in addition, densely shades the leaves. The rapid spread of the new alga causes significant damage to collections of aquatic plants.
These algae or their spores are introduced into the aquarium with new plants. They usually grow in small tufts. They attach to leaves mainly at the edges, and especially willingly to sharp tips. They are not demanding of light, but prefer illuminated places, hard water, and a high pH level. Like all algae, they successfully develop in the presence of excess nitrates. “Black Beard Algae” thrives where water contains a large amount of organic compounds and organically suspended particles. In such aquariums, its tassels form a dense carpet, covered with an abundant coating, slippery to the touch. In aquariums with clean, transparent water, they hardly multiply, locating in separate tufts on the walls, stones, and plant leaves.
Leaves of large plants or sections of stems of fine-leaved plants affected by “black beard” are removed from the aquarium, since it is impossible to separate the algae from the plant surface. Some researchers argue that the reproduction of Compsopogon stops at pH greater than 7.5, and it dies at pH greater than 8.5, i.e., in a slightly alkaline environment. Such conditions are well tolerated by most aquarium plants and almost all fish. But studies have also shown that if there are many organic suspended particles in the water, any significant change in the growth of Compsopogon, even at pH greater than 9, is not always observed. The fact is that organic particles, settling on the filaments of “black beard”, create favorable conditions for its growth and reproduction, isolating it from the adverse environmental impact.
Combating “black beard” should consist of a set of measures. You need to start by creating a slightly alkaline environment in the aquarium with a pH of at least 8. The next absolutely necessary measure should be considered the removal of excess decaying organics from the aquarium. You must necessarily reduce its population to a minimum, certainly removing fish that stir up the substrate. Direct water aeration should be minimized so that the stream of air bubbles does not lift organic particles from the substrate and create a constant cloud of turbidity. Daylight should be no more than 10 hours with mandatory spectral compliance.
Changing 25% of the aquarium water with substrate vacuuming using a siphon should be done at least once a week. With more frequent water changes, the result will be achieved faster. The water added to the aquarium must certainly be of the same hardness and have the same slightly alkaline reaction as the water in the aquarium. You should not create a strong water current in aquariums, which provides food for Compsopogon. Under all these conditions, “black beard” disappears in 1.5–2 months. Subsequently, Compsopogon may appear in greater or lesser quantities, but when maintaining appropriate conditions in the aquarium, its rapid development never occurs.
You can also restore the situation without changing the active reaction of the water and without increasing its hardness. By stopping aeration, reducing the number of fish to a minimum, and changing 1/4 of the water volume weekly, after 4–5 months you can achieve the presence of Compsopogon in the aquarium in minimal quantities, so that it does not spoil the appearance of the underwater garden. In such an aquarium with soft water having a slightly acidic or neutral reaction, the slightest violation of the regime (accumulation of organics, increased aeration, appearance of excess fish) will immediately lead to the rapid development of Compsopogon. In a container with medium hardness water that has buffering properties and generally a slightly alkaline reaction, a violation of the regime will not lead to any significant increase in the growth of “black beard”.
Identification: Compsopogon — Compsopogon.
Methods of combating red algae.
Audeuinella, Red algae, Red Brush Algae. 
