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Filtration Systems

The most important thing to remember when keeping a Koi Pond, or any fish pond for that matter, is that the enviroment must be created into a workable ecosystem with a suitable balance. You can not put the water, plants and koi in place and then expect it to remain in a good state of health. Perhaps the most essential part of this system is the way in which the water is treated, as the water conditions can be held accountable for many problems with a pond environment. Consideration must be given to the aeration within the system as it will effect all aspects of the pond environment.

To enable the koi owner to keep levels constant, a good filtration system is also essential. The basic use of a filter system is to remove unwanted debris from the water and/or convert dangerous chemicals (Ammonium Compounds) into a product that will not harm the koi environment. There are a number of filtration systems but after much consideration, we decided the best one for us was a combination mechanical / biological filter.

Water Conditions

Oxygen:
Oxygen is the life line for your pond environment. Oxygen is required by allmost all the life forms living within the pond. Oxygen enters the water by dissolving at the surface.

Water pH:
The water within the pond environment is said to be either alkaline or acidic. This depends on the amount of certain chemicals within the water. Chemicals which are of animal or vegetable origin will make the water acidic and chemicals such as chalk, marble etc (calcareous) will make the water alkaline. The pH scale starts at 0 (zero) acidic and ends at 14 (fourteen) alkaline, with 7 being neutral. Water for Koi is best suited in the range of 7.2 to 7.5, even though they can tolerate limits for 6.5 to 8. However at these levels the health and coloration of the koi will suffer.

Water pH levels can be adjusted by adding various compounds to the water. For example peat can be added to increase the acidity of the water and chalk (alkaline) can be added to decrease the acidity of the water. If the pond environment has a well balanced filtration system, so that there is no build up of organic materials the addition of such compounds should not be required. To test the pH levels of the water a pH water test kit can be purchase from your local Koi Supplier or Pool Shop.

Water Hardness:
As well as its pH level, water can be either hard or soft. Soft water is usally acidic and Hard water is usally alkaline, as hard water contain a lot of calcium. As with pH levels Koi can also tolerate a range in the hardness of the water, with a suggestion reading of about 6 degrees which is equivalent to about 107 parts per million (ppm) or calcium carbonate. Like with the pH a well balance filtration system is unlikely to allow critical levels to be reached. Water hardness testing kits can be purchased from your local Koi supplier.

Water Temperature:
Water temperature parts an important part in the overall pond environment. The higher the temperature of the water, the lower the amount of oxygen the water can contain, also at the same time the higher the water temperature the faster the multiplication of bacteria (both good and bad). The temperature of the water will also affect the colouring of the koi, the higher the temperature, the less the colurs will show themselves. Also, the warmer the water the more active the Koi will become, they will eat more food and require more oxygen. It is therefore important the you have a well balanced filtration system running at optimum during the warmer months to ensure the Koi stay healthly and stress free

Sunshine:
Sunshine will afect the temperature of the water (as discussed above), it can also affect the colour of the koi. Koi which swim in shallow ponds for long periods of time can become sunburned. This is caused by sun light affecting the colour pigments "bleaching". Therefore the pond environment should provide enough protection from the sun light. This can be in the form of shade from plants or a canopy, or a deep section of the pond as the deeper the water the less likely the fish will get sunburnt.

Aeration
The first and most important requirement for your fish pond is that it must contain moving water. Fish require oxygen as do plants and other organisms in the ponds. It is therefore essential that the pond has sufficient water movement to enduce water oxygenization. Even in nature, ponds and pools that appear to be still have water movement, as water soaks through the bottom of the pond / pool and is replenished by rainfall. There are many ways in which water can be circulated around the fish pond thus increasing the oxygen content in the water. There are also outside influenced which must be taken into consideration regarding water / oxygen levels. A prime example of this is the air temperature. On warm days, oxygen levels are depleated at a quicker rate hence you may notice fish gasping for air at the surface. This is a warning that aeration (or additional) should be added to the pond. Water that is well oxygenated circulates to the bottom of the pond if currents can be created. The least oxygenated water rises to the surface of the pond and is replenished with air. Undergravel filters are an excellent means of obtaining this current. The movement of water helps provide an even spread of oxygen throughout the entire volume of water. Other means of generating water movement is to draw the water from the pond and returning it to the pond above the ponds surface. As the water leaves the pipe, it will absorb oxygen before it re-enters the water. Ways to achieve this are by the use of a waterfall, fountains, etc. Fountains are a good way to increase oxygen levels as they increase the surface of water to air ratio by causing a disturbance (splash) on the surface of the water so more oxygen can be absorbed.

The following calculation can be used to determine the number of fish that can be accomodated without the need of additional oxygen. For every 1 square meter (10.76 square feet) of surface area, 1.6m (5.4 feet) of fish can housed. For example a pond with the dimensions of 5 x 3 meter (16 x 10 feet) gives you a surface area of 15 square meters (160 square feet). The number of fish = 28 square meters / 1.6 meters (160 sqaure feet / 5.4 feet) = 17.6 meters or 29.6 feet of fish. As the surface area of the pond increase so can the number of fish.

Ammonium Compounds / Nitrate Cycle:

Food-->Fish-->Urine Waste(Ammonia)-->Bacteria-->Nitrite
-->Bacteria-->Nitrate-->Plants & Algae-->Food and the cycle start over.

Within the pond environment there are a number of different types of bacteria. Some of these bacteria that don't require oxygen derive there energy by breaking down organic matter (ie Decaying Plant & Animal material, uneaten food etc). During the process of breaking down this organic material the release ammonia or ammounium compounds into the water. These compounds can be harmfull to fish, partically in restricted environments such as ponds and aquariums, these compounds in excess can kill the fish or in the least cause stress, thus making them more susceptible to illness. Both Koi and Goldfish have a high resistance to these ammounium / ammonia compounds, which is why Koi are oftern found in terrible water conditions.

Within the pond environment, there are other bacteria that convert these ammonia / ammounium componds into less dangerous nitrites and there are other bacteria that convert these nitrites into nitrates which are even less harmful to the fish. The nitrates can then be utilized by plants in there absorption of proteins. These bacteria require a great deal of oxygen to survive, they also require time to build up colnies.

Filtration Systems

Mechanical Filtration:
Mechanical Filters are usually the simplest of the various types of filtration systems. The basic concept of a mechanical filter is to remove the larger particles from the water. Water is usually drawn from the pond into a filtration tank which could be constructed from fiberglass, marine wood or metal to name a few, passing through various materials such as medium size gravel, plastic meshing or brushes, thus removing the particles from the water before returning to the pond. If the return point is opposite to where the water left the pond, better circulation will occur. Periodically, the filter material will need removing and cleaning to remove the build up of debris. Any larger debris that has fallen to the bottom of the tank can be drained off via an exit drain on the bottom of the tank. Mechanical filtration is usually used in conjunction with other forms of filtration systems to produce a more efficient filtration system. Combinations may include mechanical / chemical or mechanical / biological systems.

Chemical Filtration
Chemical Filters change the nature of the harmful chemicals found in the water. Chemical Filtration converts ammonia waste compounds into inert chemicals which are not dangerous to the fish. Activated carbon / charcoal and zeolite are the most popular examples of chemical filtration mediums. Both of these mediums have an excellent surface area thus can act as mechanical and chemical filters due to there porous nature. Because of the ability of these filters to change the chemical composition of a compound, it is important to check before using medications within the pond environment, as the medication may convert to other compounds, reducing the effectiveness of the medication. If the pond needs to be treated it is important to switch off the filtration system while treating the pond. A simple design of a chemical filter would be to take the mechanical filter as described above and replacing the filter material with the chemical filtration mediums.

Biological Filtration: Biological Filtration converts ammonium compounds to nitrates, which are relatively harmless to the fish. Such a filtration system may be incorporated within the pond during construction in the form of an undergravel filter or may be constructed externally in chambers containing a suitable medium as described above in the chemical and mechanical filtration systems. Certain bacteria which do not require oxygen derive their energy by breaking down organic matter. During this process, they release ammonia or ammonium compounds. These compounds in excess will kill fish though koi and goldfish have quite a high tolerance to these compounds. Even if these compounds do not kill the fish, they will stress them making them more susceptible to illness.

Within the pond environment, there are other bacteria which are able to convert these compounds into less dangerous compounds such as nitrates. These beneficial bacterias must have a place to colonize thus being the reason why Biological Filters are used in conjunction with various other filtration methods.

Undergravel Filtration:
Undergravel Filtration is a form of biological filtration and is laid on the base of the fish pond. Undergravel filters should cover at least one third of the base of the pond and have the advantage that they cannot be seen. This type of filtration system consists of a network of pipes which contain a number of holes, through which water is drawn via a pump. As the water is drawn into the pipes it is passed down through a layer of gravel which is placed on top of the network of pipes. Providing the top layer of gravel is porous it will provide an excellent medium for bacteria to colonize and break down ammonia/ammonium compounds. It will also assist in drawing larger debris to the bottom of the pond where is can then be syphoned off or vacuumed.

Vegetative Filtration
Vegetative Filters act like biological filters as they remove nitrates from the water and are usually incorporated into the water circulation system. They can be included at various locations such as ponds at the base of waterfalls, streams flowing between different ponds, etc. Examples of water plants used are water hyacinth, eelgrass, water iris and even the humble water lily just to name a few. Always check with your local pond plant supplier for recommendations on hardy plants for your country and area. Plants must be hardy so their roots can withstand the movement of water.