Spirulina algae under a microscope

Carotenoids can help Nishikigoi develop beautiful red color. Without adequate levels of carotenoid a koi's color and beauty can be lost forever. Spirulina, an algae rich in carotenoids has survived more than 3 billion years, is known as one of the world's best natural color enhancers. The name Spirulina came from the word "spiral" because it looks like a compressed spring when observed under a microscope.