Many times water is clear, yet the whites of the fish look yellow. It is the water that has turned yellow with time. The UniClear filter removes the color and fines from the pond water by using high grade, coconut shell carbon. This gives a true final plish to the water for the clearest water attainable. Use two 3-way valves during installation and flow the water through the UniClear only when you want to remove the color from the water. After color is removed, resume normal flow through your regular filtration system until the next time you need the UniClear to do its job. May also be used to remove certain medications from the pond after treatment. Carbon lasts a long time and is replaceable. Comes with a complete charge of carbon and 2" unions on the UniClear Filter.