How Koi pond filters work
Pond filters use the nitrogen cycle to purify the water for your Koi.
Filtration systems are a necessary tool in caring for the fish, plants, and water in your pond. A filter will prevent the nitrogen cycle from getting out of balance. The nitrogen cycle takes the toxins that the fish produce, Ammonia for instance, and then oxidizes them into the less toxic Nitrate. Ideally, the plants will absorb then utilize the Nitrate that's left over. They also benefit the pond by adding oxygen to the water. If the conditions are right, the process will continue indefinitely. In a pond setting without a filter, Ammonia will accumulate until it has reached toxic levels in the pond. If the pond is overstocked, then there will be a higher amount of ammonia.
When starting a new Koi pond, the levels of Ammonia, Nitrite, Nitrates and pH need to be tested on a regular basis. The ammonia levels need to stay under 1ppm and the pH readings should fall between 6.8 pH to 7.4 pH. The Nitrates need to be less than 5ppm. It takes time to balance out the levels when starting a new pond. You can "pre-cycle" a biological filter by adding Ammonia to the water four to six weeks before any Koi are put in the pond. This allows the different types of nitrifying bacteria to colonize on the filter material, so you won't get spikes in Ammonia and Nitrite levels while the Koi are in the pond.
Types of filtration
There are various types of filters used in a Koi pond that assist in creating an ideal environment. Mechanical filters such as surface skimmers, bottom drains, Cetus sieves and vortex chambers catch the organic material to remove it from the pond water. These filters ensure that the pond water is free of any solid matter. A biological filter uses nitrifying bacteria to break down the fish's metabolic byproducts, mostly ammonia, into the less harmful nitrate. A good biological filter will provide enough surface area on media to quickly establish a nitrifying bacteria colony. A chemical filter, usually used on smaller ponds, uses activated carbon to strip the Ammonia out of the pond water. Every setup uses a pump to circulate through the pond system. Air pumps and air stones are used to maintain oxygen levels in the water. If the oxygen levels fall below 3-5 mg of oxygen per liter of water, any Koi in the pond will suffer and eventually die. Fountains and waterfalls can help provide adequate aeration in the Koi pond. Ultraviolet (UV) lights are used to keep the water crystal clear by sterilizing the algae, preventing it from blooming and turning the water green. If the algae in the pond isn't controlled, it can create oxygen deprived conditions and the Koi can suffocate. The water temperature directly affects the oxygen levels as well. As the water temperature warms, the amount of dissolve Oxygen in the water decreases. As the water temperature cools, the amount of dissolve Oxygen in the water increases.
Excellent water quality is important for you Koi's well-being. A complete filter system will clean the water, keep the Koi healthy and give you piece of mind.