Chlorella (Green alga), as food supplement is rich in protein and carbohydrates. It yields about 30% proteins, 15% lipids, 30% carbohydrates and 5% ash. Spirulina (blue-green alga) is one of the richest sources of protein and vitamin B2. In long range space exploration, scientist have turned to Chlorella and Spirulina to use them as portable oxygen generators and food sources.