Planktonic algae are floating microscope plants that are normal and essential inhabitants of sunlit surface waters. There are literally millions of floating planktonic algae and these color pond water shades of green, blue-green, brown or variations in between. Planktonic algae that color the water is often called a “bloom” or “algae bloom”. Many species of algae are involved in algae blooms and these species change over time based on temperature, light, nutrients, and other factors.