Spirulina is a type of blue-green microalgae that is able to grow in both fresh and salt water and is consumed by humans and other animals. There are two species of the spirulina plant, including Arthrospira platensis and Arthrospira maxima. Arthrospira platensis and Arthrospira maxima are cultivated worldwide and used both as a dietary supplement (in tablet, flake and powder form) and even whole food — and even for livestock and fish feed.