Jason,

Many ponds now take this approach with a natural algae/duckweed/plant filter.

It is practiced here in FL as it is copied from the natural wetlands process in the glades..........We have finally figured out that Nature does sort of know what it is doing lol

Some farms now use heavily planted areas to filter the water they used to fertilize the crops which are heavy in nutrients and have shown that the levels of nitrate, phosphate, etc are lower than that which came in to them.