OK, short and to the point:
Cyanobacteria have Heterocysts (anaerobic factories for nitrogen fixation) and these are the specialized cells of nitrogen that convert diatomic atmospheric nitrogen (N2) into biologically available forms, nitrate and nitrite. Nitrate (NO3) & Nitrite (NO2) are nitrogen-oxygen chemical units which combines with various organic and inorganic compounds. When starved for nitrogen, specialized cells called Heterocysts, which differentiate, from the photosynthetic vegetative cells form at regular intervals along each filament strand. This process helps the bacteria to survive.
Side note:
Many strains of cyanobacteria produce potent toxins that can harm fish, livestock, pets, and humans. Certain strains of cyanobacteria produce the following toxins: Microcystins, Nodularin, Anatoxins, Saxitoxins, Cylindrospermopsins, Lyngbiatoxin-a, Aplysiatoxins, and Lipopolysaccharides (LPS). Although some toxins appear to be confined to specific forms of cyanobacteria.
Cyanobacteria are formed due to slow-flowing, warm, nutrient-rich waters. Proper exportation through skimming, nutrient depletion (waste removal), quick or rapid water movement & dropping water temperature (76-78 degrees) may aid in unwanted blooms. Lighting also plays a key role in vegetative photosynthesis. IMHO, limiting your illumination of the system is a band-aid and only a temporary fix to the bigger problem. Who wants to look at a black box with water? Not to mention if you have light-loving life forms in the system, you'll be starving the symbiotic zooxanthellae from the tissues of corals/polyps. Hence, bleaching.
Not a plug but...
Red Slime Remover is very useful in treating an infected system with cyanobacteria. Although ingredients are voided from packaging, I have experimented with a few different antibiotics. Cephalosporin antibiotics (ie Keflex, Keftab or Cephalexin, the First Generation Cephalosporins) have the ability to destroy gram-positve bacteria and a few gram-negative varieties. IME, these antibiotics work well in the marine aquarium, without stress to other life forms. 1 - 500 mg capsule opened/dissolved/mixed in a glass of luke warm RO/DI water per 50 gallons of water, worked well for me. A second dosage may be needed to totally eliminate the problem and prevent reoccurrences. This treatment should be administered without the aid/assistance of skimming or carbon removal through mechanical filtration for at least 24 hours to be effective.
HTH a little
