The cyanobacteria of concern are generally freshwater or brackish water species and are commonly found as 'blooms' in slow-flowing, nutrient-rich waters, usually in the warmer months of the year (when both temperature and sunlight are optimal). Blooms are often found in farm dams or ponds where very little mixing occurs, allowing warm water layers to form near the surface. As a result, highly toxic 'scum' material often forms on the water surface, creating a potential danger for livestock and, indeed, humans.

Below is a list of known cyanobacteria and the toxins they produce.