Algae are classified into two main categories known as macroalgae and microalgae. Macroalgae are the macroscopic, multicellular type of algae while microalgae are microscopic and unicellular. Likewise macroalgae are used as prebiotics for farm animals as they can increase the growth of beneficial gut bacteria, which in turn improves the intestinal health and growth performance of the animal. Algae are classified into two major classes namely macroalgae and microalgae based on their size. Information about the total diversity of microalgae in the Mascarene Islands is very limited as no studies have yet been conducted. Both macro- and microalgae can be considered as very good sources of bioactive compounds comprising of carbohydrates, proteins, lipids, sterols, antioxidants, minerals and vitamins. Macroalgae normally consist of 80-90% water and their dry weight encompasses 50% carbohydrates, 1-3% lipids and 7-38% minerals. Microalgae have such a high level of lipids that they are considered as an alternative source for production of biodiesel.