Blue-green algae is a group of 1,500 species of microscopic aquatic plants. The two most common species used for human consumption are Spirulina maxima and Spirulina platensis. Spirulina is rich in protein and also contains carotenoids, vitamins, minerals, and essential fatty acids. People who do not consume several servings of vegetables per day could benefit from the carotenoids and other nutrients in blue-green algae. It is a complete protein and can replace some of the protein in a healthy diet. It comes in powder, flakes, capsules, or tablet form. Non-harmful edible algae of particular nutritional importance to vegans/vegetarians include the sea vegetables: wakame, arame, dulse, hijiki, nori and kombu. Both Spirulina and Chlorella (another important, freshwater, blue-green algae) are easily digested, extremely high in nutrients (Spirulina is 60-72% protein and Chlorella is 60%) and offer many important health benefits. NASA has chosen Spirulina as an ideal food to grow on space stations. It is the most efficient, oxygen-generating, high-potency food known.