Bog Filters


Imagine a pond filtration system that helps maintain water quality and produces beautiful blooms. It may sound strange, but that is exactly what a bog filter does. Applying the principles of bioremediation, bog filtration employs a lush planting of gorgeous, water-loving plants to remove excess nutrients and improve water quality. Very little equipment is required to install this low maintenance filtration system. And best of all, unlike bulky conventional filtration systems, you'll want to show off your bog filter rather than conceal it. Learn more about this fascinating aspect of water gardening and find out how you can incorporate a bog filter into an existing water feature.


What is a bog filter?

Pond water is transported directly to plant roots and biologically filtered water returns to the main pond.


A bog filter is an area dedicated for the dense planting of water-loving marginal or bog plants. It is a smaller, supplementary pond usually 10-20% of the size of the main water feature. The bog filter can be located inside or adjacent to the main pond. Whether it is internally or externally located, the bog filter must be connected to the main pond by a water circulation system consisting of plumbing and a pump. As water from the main water feature is fed into the bog filter, plants remove the nutrients and the biologically filtered water is returned to the main pond.


Benefits of bog filtration

In addition to water-clarifying benefits, bog filters provide the avid water gardener many pleasures. Bog filters dramatically increase planting options and offer a satisfying project that enhances an existing water garden.


Principle behind bog filtration

In essence, a bog filter is a natural wastewater management system for your pond. This effective example of biological filtration relies on plants to extract such pond pollutants as organic waste, ammonia, nitrite, nitrate, and phosphate before they can accumulate and negatively affect water quality. This natural filtration restores balance to the pond environment by increasing the ability to process or export excess nutrients. The result is cleaner, clearer, and healthier pond water.


What makes bog filters different from conventional pond planting is the manner in which the plants are grown. In bog filters, plants are grown hydroponically in relatively coarse, nutrient-poor substrate (pea gravel). This planting method "trains" the plants to search for nutrients in water rather than in substrate or planting media. Conventional potted pond plants passively remove nutrients from fertilized planting media and rely minimally on pond water for nutrients.


Furthermore, bog filters incorporate a circulation pump. This pump actively draws water from the main pond and introduces it directly to the plant root system. A diffusion system, similar in principle to a water fountain, is placed at the bottom of the bog filter. This water conduit system relies on the up-flow principle so water drawn from the main pond percolates up through the planting media and bathes the plant root with nutrient-rich water. This method not only increases water circulation through the root system for healthy plant growth but also provides additional mechanical filtration.

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