Low Maintenance Filtration Systems

What type of pond filter do I need to maintain healthy water conditions in my pond?

There are three types of low-maintenance filtration systems used to maintain a pond at a healthy state: natural filtration, particulate filtration, and bio-filtration. The role of the pond filter is not to remove physical dirt and keep the water sparkling clean, as some may believe. The most important part of the filters job is to act as a mini sewage system for the pond. When physical waste such as fish waste, excess food or decaying organic material falls to the bottom of the pond it starts breaking down and releases toxins into the water. As the water passes through the filter the helpful bacteria break down these invisible toxins and any other organic waste, which get caught up in the filter.

Natural filtration uses plants to perform the filtering functions within the pond. This refers to the biological process of using up excess nutrients, phosphates, and minerals in the water to prevent algae plants from growing. To achieve this you will need enough plants to cover about two thirds of the pond area. These plants, along with helpful bacteria occurring naturally in the pond, will then use and digest any toxins left by fish and rotting organic waste, hopefully providing a good natural balance and a healthy pond. It is important to remember that, if using a natural filtration process the plants should be well established before gradually introducing fish to your pond. The plants most often used for a natural filtration process are the submerged aquatics, referred to as oxygenators.

The benefits of plants for filtration are:

  • Aquatic plants consume toxic compounds such as ammonium, nitrite and nitrates,
  • Aquatic plants remove toxic heavy metals and other pollutants from the water,
  • Aquatic plants provide surface areas for all types of beneficial bacteria thereby improving water quality,
  • Aquatic plants oxygenate the water and remove CO2 from the water.

Natural plant filters can be any shape, but rectangular is the easiest one to build, and it only needs to be anywhere between 10 inches and 18 inches deep. First calculate total surface area of the main pond you are going to filter, estimate 10% of surface area or more. And that is the size of the plants filter surface area you will build. To frame the filter up, you can use pressure treated lumber, block or railroad ties. Rubber or PVC pond liners are excellent liner material for the filter. Shape the bottom to form a low point where the bulkhead drain will be installed. The drain will help to flush sediment from the natural pond filter.

articulate filtration is also referred to as pond skimmers. This is designed to remove all the floating debris on the pond surface. A large-particle filter can remove all the leaves, bits of grass and other organic matter that may fall into a pond. If you skim off this organic matter from the top while it is floating, it will not rot on the bottom. Rotting organic matter takes up oxygen so eliminating it allows the plants and fish to use the oxygen for a healthy existence. The pond skimmer needs to be cleaned out once a week (or more when leaves are falling).

Bio-filtration acts to balance the water chemistry. It is based upon the work of nitrifying bacteria inside the filter that convert ammonia to nitrite and then to nitrates. It is not used to keep the water clear unless natural plant filtration is used as well. There are many manufactured bio-filters in the marketplace.