The color of the water tells us what the water may or may not be lacking as far as nutrients. Decomposing leaves and debris release a tannic acid that can turn the water brown. High mineral contents in the water cause it to appear white in color, again not the best for the ecosystem. Everyone wants crystal clear water when actually clear water does not support the nutrients necessary to do it's part in the ecosystem. A slight tint of green is the ideal water for a backyard pond.
Green water is healthier in terms of oxygen production and buffering of pH changes.
They also produce larger and more diverse food sources for other pond life. The plants surrounding the pond are not only a beautiful addition to any landscape but play an important role in the ecosystem as well. Aquatic plants use the carbon dioxide and nutrients that are produced from the bacteria and life on the bottom, combine with the sunlight to nourish themselves. Without plants the nutrients are still being produced but have nothing to use them up, therefore overloading your system. This causes algae to grow to use up these nutrients.