Bog filtration is often overlooked or forgotten about in a pond. The natural process of plants consuming nutrients is Mother Nature's way of filtering the water in any given body of water. Bog filtration is most effective when the nutrients in the pond are able to pass near the roots of aquatic plants. As the nutrients pass by the roots, the roots "grab" the nutrients and consume them as a fertilizer. This is much like adding pellet fertilizer to your lawn or flower beds. A properly designed bog filter can outperform most commercially available filtration systems…. not to mention are only a fraction of the cost.Bog filters will help collect and breakdown the same nutrients that are responsible for algae blooms. By allowing the bog filter to do its job this will reduce the need to add expensive algaecide products which will also inhibit plant life that you want.The best design for a bog filter is an upflow system. this is where the "dirty" water flows upward through the plant roots before returning to the pond. A bog filter can be outside the pond in an external small pool or some adequate container connected via plumbing, at the head of the stream or in an area in the pond itself.Basically, what you will need is an area which is at least 12″ deep and whatever square footage you want. For design's sake we are going to construct a 24″wide x 24″long and 12″deep bog filter. I suggest first installing a supply line to the bottom of the filter. Then create a "sub" floor that sits 4″s from the bottom. This will allow heavy sediment to settle before rising to the surface. Next I would fill the rest of the area with a small 3/4″ and smaller rounded gravel. This will act as a media or "soil" for the plants which will be planted in this filter. It is always a good idea to wash the gravel before placing it in the filter to remove any sand, dirt or other debris. After the gravel has been washed, it is now time to plant the aquatic plants. I like to remove the soil from the potted plants and wash the roots off before placing them in the filter. These roots will soon grow throughout the gravel filtering the water as it passes.