It is highly diatomaceous , an intense green color, and subject to algal blooms. The idea is that highly nutrified water is allowed to flow through gravel beds where nutrients are taken up in plants. Though similar filters have been successful elsewhere, this one quickly became clogged by diatoms and fine material that was in the gravel, and it has not produced significant amounts of clean water. Observe the intense green color of this highly eutrophied water. Highly nutrified water from Mitchell Lake passes through a gravel bed where nutrients are taken up in plants.
Water is collected in the trough at right.
However, this filter is plugged - water should not be moving over the top of the gravel as seen here flowing from the left center.