Water is funneled from a filthy pond through a series of tanks. Pictured above are the first two. They contain a mixture of microorganisms, algae, and small fish. As the water moves through each of the tanks, it becomes a little cleaner. The tanks themselves become smaller, since less material is needed to clean the water.
Finally, after it has passed through 10 tanks, the water is nearly contaminant-free! How clean is it? Clean enough to be used on a mini garden of wild ginger plants. Including this one, which is so happy, it's flowering!