Differences between fungi and algae: Fungi are unicellular or multicellular eukaryotic organisms. Algae are aquatic eukaryotic unicellular or multicellular organisms that can prepare sugary foods through photosynthesis. Their bodies are not divided into roots , stems and leaves. They are capable of trapping nitrogen gas in the air. They cause food oxidation in the respiratory system. There are many types of algae growing in the world. Some of them are unicellular and some are multicellular . They can grow in fresh water and salt water .