Larry Lunsford

To successfully keep Koi, you must filter their water. There are several types of filters that are of use for Koi ponds including: mechanical, biological, UV, chemical, ozone, protein skimmer, and more. Your pond will need a filtration system that includes at least mechanical and biological. For better water quality, you may want to use additional filtering as well.

There are a wide variety of filters and media to choose among. You can buy one of the many commercially made filters or you can make your own. A sampling of the commonly used filters is discussed below, starting with the simplest - smallest - cheapest types and working towards the more complicated - larger - expensive types. Many filters and media are capable of performing both mechanical and biological filtering, some can only perform one type of filtering.

There are many factors to consider when choosing your filter. Some of the factors include: quality of mechanical filtration, quality of biological filtration, size, cost, capacity, open flow / pressurized, ease of maintenance. Here's some terms you need to be familiar with to discuss filters:

Activated Carbon - Carbon is used to remove chemical impurities in the water. Carbon is typically used in a pressurized container and the pond water is forced through the carbon. Carbon filtering is normally used only on special occasions when the pond keeper is trying to remove some specific contaminant. Carbon is good at removing chlorine. Carbon will not remove ammonia. Carbon cannot be easily cleaned or recharged.

Aerobic - having oxygen present. The bacteria in a Koi pond biofilter are aerobic and require high levels of oxygen to fucntion properly.

Air Diffuser - A device for creating small bubbles. Common material for air diffusers include: fused silica (air stones), porous wood, and perforated rubber.

Air Dome - A type of cover for bottom drains that incorporates an air diffuser. By having air bubbles rise directly above the bottom drain, an upward flow of water is created. This also creates an inward flow of water around the bottom which helps sweep debris toward the drain.

Ammonia (NH₄) - This is the primary waste product of Koi. It is toxic to Koi and must be removed. Most ponds rely on biofiltration to eliminate ammonia.

Ammonia Cycle - This is the progression of waste through your pond. There are many factors involved in the ammonia cycle. The important points are: Koi give off ammonia as their primary form of waste. Ammonia is toxic to Koi and must be removed. Bacteria convert ammonia into nitrite. Nitrite is also toxic to Koi. Bacteria convert nitrite into nitrate. Nitrate is relatively harmless and is also removed by yet another type of bacteria. The Koi and bacteria both require oxygen. The bacteria consume buffers and produce acid as part of processing ammonia and nitrite. Buffers must be replaced to maintain a healthy pH.

Anaerobic - lacking oxygen. Anaerobic conditions foster the growth of harmful bacteria. Anaerobic conditions are found in stagnant water and sediment. You should avoid anaerobic contitions anywhere in your pond and filters.

Back-Flush - Reversing the flow of water through a filter in order to flush out waste.

Balance - This is a man-made ceramic material that resembles gravel. It is very porous and is lighter than gravel. It is good for biological and mechanical filtering.

Bio Balls - Bio balls are plastic media that are designed for biological filtering - they do not perform any mechanical filtering. They come in a variety of shapes and sizes. The typical bio ball is 1" to 3" in diameter and looks like a pin cushion. Bio balls pack a lot of surface area into a small volume and they do not collect much debris. Bio balls may be used either submerged or in trickle towers.

Biofilm Carrier - This is a floating plastic media that is intended to be used in a fluidized bed mode. It consists of plastic elements about 1/4" each side. It resembles pieces of cut up drinking straws. The pieces have ribs and cross members to increase surface area. This media does not perform mechanical filtering, but is very good for biological.

Biological Filtration - relies on biological activity to process waste. In your Koi pond, ammonia is the primary waste product of Koi and a biofilter is the most practical means of processing ammonia. A biofilter is simply something that has a lot of surface area for culturing bacteria. The bacteria do the actual work of processing ammonia - the filter is just a place for the bacteria to grow. In time, every wet surface in your pond will become coated with bacteria. Usually, you need more surface area for bacteria than just the sides of the pond itself and you will include a biofilter which has a media with a lot of surface area to grow bacteria.

Bottom Drain - A drain installed at the bottom of the pond which allows debris to be easily removed. A bottom drain is essential to keep debris from accumulating in your pond. The bottom drain should allow for easy collection of debris, but prevent fish from being drawn into the filter system.

Brushes - The brushes used in Koi pond filters resemble giant test tube cleaning brushes - they're around 4" in diameter and range from 12" to 48" long. Brushes are good at both mechanical and biological filtering. Brushes are good at collecting floating particles that are too light to settle out. Brushes have lots of surface area which makes them well suited to biological filtering. In most applications, the brushes are hung vertically and the water passes horizontally. To clean, simply remove brushes from container and hose off.

Bubble Bead - This type of filter uses floating plastic beads for mechanical and biological filtering. It has an hour glass shaped chamber. In filtering mode, water flows up through the chamber and media. The beads pack at the top and form a tight enough media that they trap particles of debris. In cleaning mode, water is drained out the bottom and air is drawn in below the waist in the hour glass. The incoming air bubbles churn the beads as they pass by the waist which loosens debris. Bubble bead filters typically require a pump pressure of 5psi - 10psi. Sometimes the bubbles do not provide adequate cleaning and the filter requires back-flushing.

Buffers - These are chemicals which help stabilize conditions in your pond. A buffer will hold the pH to a particular value. When the pH of your water is lower than the natural pH of the buffer, the buffer will raise the pH. When the pH of the water is higher, the buffer helps to lower the pH. Buffers get consumed in the process of buffering your water. The most common buffer is baking soda.

CFM - Cubic Feet Per Minute, a measure of flow (usually applied to air flow).

Channeling - The tendency for the media to become clogged and for the water to flow only through a small channel in the media. Once channeling occurs, filtering becomes inefficient - flow rates in the channel area are too high to facilitate mechanical filtering and contact area is too small for biological filtering.

Crushed Shells - Shells are available at feed stores (they're used as chicken grit). Shells are normally used in ponds to help keep calcium and carbonate levels up. To help them dissolve, they should be put in an area with high flow. Eventually, shells will become covered with a coat of bacteria. Once this happens, they act more as a biofilter and stop dissolving. Shells need to be thoroughly cleaned periodically to eliminate the layer of bacteria, algae, and debris.

Diatomaceous Earth (DE) - DE is a very fine powder that is the fossilized remains of single cell animals. A DE filter contains a pressurized chamber with a screen that is coated with DE. The DE needs to be periodically replentished. A DE filter is used primarily for mechanical filtering. Some Koi keepers will use their DE filter for special occasions when they want their water to be ultra clear. DE filters are typically very expensive and require high pump pressure.

Down Flow - A filter with submerged media and the water flows down through the media. Many down flow filters use air bubbles injected below the media to clean the media. Down flow designs have the advantage that you can easily see how much debris has accumulated since it is on the top. A disadvantage of down flow desing is the reliable flow of water. If you gravity feed to a down flow filter and pump back to the pond, the pump can starve for water if the filter becomes cloged. If you pump to a down flow filter and allow water to return to the pond by gravity, you can over flow the filter and pump the pond dry if the filter becomes cloged. You can prevent overflow problems by having plumbing that will allow water to bypass the media if it becomes clogged.

EPDM - A type of rubber used to make pond liners. EPDM is also used in roofing. EPDM is strong, flexible, and resists UV. Use EPDM that is fish safe - some roofing material is coated with chemicals to inhibit algae and fungus and is toxic to fish.

Flooded Suction (pump) - A term applied to in-line pumps indicating that the water must flow by force of gravity to the pump intake. A flooded suction pump cannot suck in water from any height and so must be placed below the water line. You can devise check-valves to allow you to prime a flooded suction pump and operate the pump above the water line.

Fluidized - A filter whose media that is kept suspended in a turbulent flow of water (like lotto balls in the mixer). Fluidized media is usually very good at biofiltering and typically provides no mechanical filtering.

Fluidized Bead - This type of filter uses plastic beads for biological filteing. The design of the chamber and plumbing and the choice of sinking or floating beads keeps the beads fluidized. Fluidized bead filters are pressurized, but do not typically require a lot of pressure to operate.

Fluidized Sand - This filter uses sand to provide biological filtering. This filter uses a tall vertical chamber with the water flowing up to keep the sand fluidized. Sand filters are very good for bio filtering since they pack a lot of surface area into a small volume. Their disadvantages are: they require high flow rate and a well controlled flow rate, and they can quickly go anaerobic if the pump stops.

Foam Fractionator / Protein Skimmer - This type of filter removes pollution from the water with bubbles of air. Pollutants such as proteins and small particles will stick to the surface of bubbles. If your pond has a film on the surface that looks like oil or you notice foam near waterfalls, you could benefit from using a protein skimmer. Skimmers also work better when you use salt in your pond (salty water produces more foam but don't use salt just to help the skimmer). Protein skimmers are usually in the form of tall pipes or chambers. Bubbles are produced by an airpump driven airstone or by a venturi. Bubbles laden with pollutants are collected at the top of the filter and removed. There are a variety of commercial units available. You can also make your own using DIY plans. The things to look for are: fine bubbles (the smaller the better), lots of bubbles (the more the better), long contact times (the more contact time the better - contact time is proportional to the size of the chamber, convoluted chambers don't necessarily improve performance), quality of construction, ease of cleaning, ease of removal of waste foam. A protein skimmer will generate bubbles with either a venturi or an airpump. Skimmers using a venturi will require greater pump pressure.

Gravel - Most any type of common gravel may be used as a Koi pond filter media. It has the advantage of being cheap and readily available. Gravel is good for mechanical and biological filtering and may be used either submerged or in a trickle tower. The main disadvantage of gravel is maintenance. Cleaning a gravel filter is hard work and requires getting up close and personal with the dirty media.

Gravity Feed - Relying on the force of gravity to provide water flow. Sections of your pond that use gravity feed should use large diameter pipe to allow sufficient water flow with minimal head loss. Under sizing gravity flow pipes can result in your pump running dry or large swings in filter water level (between pump running and stopped).

GPH - Gallons Per Hour, a measure of water flow. GPM - Gallons Per Minute.

Head / Head Loss - The loss of pressure (head) as a result of water flow. Head loss occurs as a result of friction. Head is typically measured in inches, feet or PSI. One PSI = 2.2 feet = 26 inches of head. Head pressure of X feet is the pressure produced by a column of water X feet tall.

Horizontal Flow - A filter with submerged media and the water flows horizontally through the media.

In-Line Pump - A pump that operates out of the water. It has connections for water in and out. In-line pumps are generally more efficient than submerged pumps. The most efficient (those that move the most water for the least electricity) and larger size pumps (over 1000 gph) on the market today are generally in-line, flooded suction style. Be sure to place in-line pumps in a location that will not become flooded (by rain, pipe leak or accidental over filling the pond) which can destroy the pump. You may want to incorporate a sump pit and sump pump in the bottom of the pit for your in-line pump.

Japanese Matting - See Padding.

Lava Rock - Lava rock is good for both mechanical and biological filtering. It has lots of surface area to support biological filtering. It has lots of crevices to collect debris. Lava rock is cheap and readily available. Lava rock may be used either submerged or in trickle towers. The main disadvantage of lava rock is that it is difficult to clean. If you use lava rock, you should put it into mesh bags (such as nylon bags used for cleaning delicate clothes in the washing machine) in easily manageable quantities for easy removal and cleaning.

Leaf Trap / Leaf Strainer - A small filter designed to collect large debris. Leaf traps are generally fitted to the inlet of in-line pumps to strain out large debris that could clog the pump impeller.

Mechanical Filtration - physically removes particles from the water. The particles that will be in your water are things like fish waste, leaves, grass, dust, pollen, etc. You need to remove particles from the water before they start to accumulate and decompose which creates other health problems.

Mesh Screen - Some filter devices use very fine mesh screens to filter solids down to around 100 microns in size. The screen is typically made of nylon or stainless steel. These filters also include mechanisms to continuously flush the screen to prevent clogging. Removing fine particles will result in very clear water and will also reduce the load that the biofilter must handle (since many fine particles would otherwise become debris that must be broken down biologically). Mesh screen filters are typically expensive due to the need for a self cleaning mechanism.

Nitrate (NO₃) - Nitrate is produced by the bacteria that consume nitrite. Nitrate is relatively harmless to Koi. Nitrate will contribute to the growth of algae.

Nitrite (NO₂) - Nitrite is produced by the bacteria that consume ammonia. Nitrite is toxic to Koi. Nitrite is typically removed by biofiltration.

New Pond Syndrome - This is problems of water quality that are typical for a new pond. The first is an ammonia spike. A new pond will have no ammonia and also no biofilter. When fish are added, the ammonia starts to build up. The ammonia will continue to build up until the biofilter becomes established and consumes the ammonia. As the ammonia eating bacteria multiply, the ammonia level goes down, but the bacteria give off nitrite which causes a second spike of nitrite. Eventually, nitrite eating bacteria get the nitrite under control too. Another new pond syndrome is the tendancy to turn green due to suspended algae. Algae grow rapidly by feeding on the ammonia, nitrite, nitrate. Sometimes, the natural balances will eventually result in clear water. Sometimes, the only way to rid your pond of suspended algae is to use a UV filter.

Open Flow - A filter that has little resistance to water flow. Generally, the top is open to access the filter media.

Ozone - These filters purify water by oxidizing impurities with ozone (O₃). The oxidation process kills organisms like algae and bacteria. The oxidation process also converts toxic substances like ammonia into harmless products. When using ozone, you must be careful not to allow it to come in contact with your Koi as it will destroy their gills much like chlorine does.

Padding - There are many types of filter padding available. Most of it looks similar to material used for your home furnace air filter. Note - most furnace air filters are NOT suitable for Koi ponds. Filter padding comes in a wide variety of types which vary in thickness, density, rigidity, material, colors, and durability. Filter padding performs well at both mechanical and biological filtering. Filter padding can be cut to fit any container. Filter padding can be used in chambers with the water flowing up, down, or horizontally. Cleaning filter pads can be done by simply removing the material from the chamber and hosing it off.

Pea Gravel - Pea gravel is good for mechanical and biological filtering and may be used either submerged or in a trickle tower. Pea gravel is a little better than regular gravel since its small size gives it more surface area per cubic foot and its round shape is less prone to clogging and channeling. The main disadvantage of gravel is maintenance. Cleaning a pea gravel filter is only slightly better than regular gravel.

Pressurized - A filter that requires pressure of a pump to force water through the media.

Protein Skimmer - see Foam Fractionator

PSI - Pounds Per Square Inch, a measure of pressure. One PSI = 2.2 feet (of water) = 26 inches (of water).

Rotating Biological Contactor (RBC) - An RBC is very good at biological filtering. RBCs do not perform mechanical filtering. A RBC has a cylinder of filter media that is partially submerged (typically close to 1/2 submerged). The axis of the cylinder is parallel to the surface of the water. The cylinder of media rotates. Rotating the media allows all the media to cycle between submerged and wet/dry. RBCs make very efficient use of their media since it all comes in contact with the water and also gets good aeration. The media cylinder can be made of many types of media. The RBC media cylinder may be rotated by a motor, by moving water, or by an airpump. The main disadvantage of RBCs is that if they ever stop rotating (due to pump failure, power outage, etc.) the exposed half of the cylinder dries out and then the cylinder becomes unbalanced and difficult to keep rotating.

Sand Filter (swimming pool style) - This filter uses ordinary sand for mechanical and biological filtering. The chamber is typically cylindrical or spherical. Water flows down through the sand. Cleaning is accomplished by back-flushing. Sand filters are very good at bio and mech filtering. Their main disadvantage is the large head loss and high pump pressure required.

Self Priming - A pump which is capable of generating enough vacuum to start the flow of water. Self priming pumps are required where the pump needs to be placed above the water line and there is no means of priming the pump. Most of the pumps that are suitable for ponds are not self priming.

Settling Chamber - This is simply a large container where heavy solids can settle out of the water. A settling chamber needs to be large enough to allow time for particles to settle out. If the chamber is too small or the water flow too fast, particles will remain suspeneded and will not be removed. Baffles in the chamber can help direct the water flow to improve settling of solids. The advantage of this filter is its simplicity. The disadvantage is that it needs to be large to be effective.

Siporax - A man made ceramic material that is very porous. This material packs a lot of surface area into a small space. Siporax is also very expensive and needs to be kept clean. Allowing debris to cover the material will negate the benefit of having a large internal surface area.

Spray Bar - A pipe with a series of holes in it used to distribute water over a larger area and to increase aeration of the water.

Spring Flow - This is a plastic media that is a long, thin, textured strip - it resembles plastic strapping used to secure boxes. Spring flow is used for biological filtering. It comes in a small box as a tightly wound spool. Once unwound, it has a lot of available surface area for bacteria. Cleaning is accomplished by simply swishing the media in a tub of pond water to clear away debris.

Submerged - Media that is completely under water.

Submerged Pump - A pump that is placed in the body of water that it is pumping from. Submerged pumps tend to be smaller capacity (under 1000 gph). Many submerged pumps have poor energy efficiency. Some submerged pumps are oil filled and can be hazardous to your fish if the oil leaks from the pump. Be sure to check the wiring on submerged pumps and use a GFCI (ground fault circuit interrupter) to prevent electrocution of your fish or yourself. One of the most common types of submerged pumps is sump pumps. Sump pumps are usually very inefficient and use oil filled motors.

Surface Skimmer - This is a device that draws water off the surface of the pond. The advantage of drawing water off the surface is that you quickly remove things like leaves, dust, and pollen before they have a chance to sink and become rotting debris. Points to check when buying a surface skimmer are weir design and size of device. The weir is pivoting door at the entrance of the skimmer. The weir is designed to swing up and down so that it stays with its top at the water surface and only allows surface water to be drawn in. Some skimmers have curved intakes such that the arc of the intake follows the arc of the weir. This design will not allow a Koi to get past the weir and become traped inside. Check the size of the leaf basket when shopping for a skimmer. If you have a lot of trees near your pond, you'll want a large basket that can handle the heavy load of leaves in the fall. Some skimmers have a hatch in the top for removing and cleaning the leaf basket and others are accessed from the front. The top hatch model is easire to clean. The front access models are less obtrousive.

Trickle Tower - A trickle tower is a filter that consists of a vertical column of filter media with water trickling down from the top. The media is above water (not submerged). Trickle towers are very good at biological filtering due to the large oxygen transfer. Most any media can be used in a trickle tower - avoid using medias that will collect debris. Trickle towers are generally home made devices that use anything from trash cans to milk crates to hold the media. Water is pumped to the top of the tower and distributed over the media by a spray bar or similar device. The water is collected at the bottom and returned to the pond by gravity. Trickle towers require little maintenance (occasionally hose off media to clean out debris and clean out holes of spray bars). The main disadvantages of a trickle tower is that it must be located above pond level and that it can cause significant water cooling if used in periods of cold weather (trickle towers shouldn't be used at all if temperatures drop below freezing).

Ultra Violet (UV) - UV is used to control algae. Algae is killed by exposure to high levels of UV. A UV filter consists of one or more pipes with UV bulbs (normally in a quartz sleeve) placed in the center of the pipe. Pond water is pumped through the pipe. Floating algae in the water gets killed by exposure to UV as it passes by the bulb. Other organisms such as bacteria and viruses can be killed by UV, but require much greater UV intensity than is normally used to control just algae.

Under Gravel Filter - This is a filter that consists of gravel in the bottom of the pond. Pipes are installed below the gravel. Water flows through the gravel (usually down flow) and the gravel performs biological and mechanical filtering. In some installations, the balance of the pond is such that the gravel never needs cleaning. In most ponds, the gravel will require cleaning. A UGF is the worst type of filter to clean. In some cases, UGFs which are not cleaned frequently enough go anaerobic resulting a total fish kill.

Up Flow - A filter with submerged media and the water flows up through the media. The advantage of up flow over down flow is that it is more reliable with regard to water flow. If you setup an up flow filter so that you pump to the filter and allow water to flow out the top and return to the pond by gravity, it is very reliable. A disadvantage of up flow is that it is more difficult to check the amount of debris accumulated and is more difficult to clean.

Venturi - A device which mixes air with water. Typically they have a small passage with an airline attached. The flow of the water through the passage creates a vacuum which draws in air (similar to a carbeurator or paint sprayer). The air is mixed with the water exiting the venturi. A venturi needs to be properly sized to provide adequate aeration without excessive pressure loss.

Vortex Settling - This is simply a round container with a cone shaped bottom. Water enters at the side near the middle and exits near the top. This causes the water to rotate in the chamber. Heavy particles of waste will fall to the bottom of the chamber where they can be easily flushed out. The advantage of this type of filter is that it is very simple and reliable. The disadvantage is that they are relativley large and expensive. If you flow water through the chamber too fast, it will not collect debris.

Wet/Dry - Media that is held above the water. Water is allowed to flow over the media. The large volume of air that is available to wet/dry media allows it to operate more efficiently as a biofilter than if it were submerged.

Zeolite - This is a name for many varieties of naturally occuring clay. In the pond, zeolite is used to remove ammonia. To be effective, the water must flow through the zeolite - use a pressurized container or put the zeolite in a high flow area. Once zeolite becomes saturated with ammonia, it can be re-charged by soaking it in salt water (soak over night in a bucket of water that has as much salt dissolved as possible). It is a good idea to "pre-charge" your zeolite by soaking in salt water even before its first use. Do not use zeolite and salt in the pond at the same time. The capacity of zeolite to absorb ammonia varies greatly - some samples won't absorb ammonia at all.

Filter Water Flow - Pressurized filters require a pump to force water through the filter. For pressurized filters, location relative to the pond level is not much of an issue. For an open filter chamber, there are three ways that water can flow through your filter: up, down, or horizontally. There are two ways that water may be feed into the filter: by gravity or by pump. Here are some of the issues with the various flow arrangements.

Gravity Feed - Your feed pipes need to be of large enough diameter and short enough run that there is not too much variation in the water level in your filter. Large fluctuations in water level can result in a system where the filter may overflow if the pump stops, or the pump may be starved for water if the pond is a bit low or the filter gets dirty.

Pump Feed, Up Flow - With this arrangement, there is little concern for water flow. The pump can easily overcome small changes in the resistance of water flow as the filter becomes dirty. The main disadvantage of this configuration is that dirt accumulates on the bottom where it cannot be seen and cleaning requires removing all the media.

Pump Feed, Down Flow - With this arrangement, you must take precautions against overflowing the filter. If the filter becomes clogged, the pump will keep sending water and overflow out the filter. With this configuration, you should include a bypass to allow water to flow even if the media becomes clogged.

No matter what type of filter you use, there are common elements to look for. All the water should flow through the media - there should not be gaps between the media and chamber that would allow water to bypass the media. Water should flow evenly through the media. The media should be easy to clean - a hard to clean filter generally gets neglected and water quality suffers. Your biofilter needs a lot of oxygen to operate. You can increase oxygen in the biofilter stage by using an air pump or by using a spray bar at the inlet.

The figures below show a variety of common pond and filter arrangements. The figures progress from small and simple to larger and more elaborate (and expensive). Your pond, no matter how small or large, can benefit from the best filtration possible. When planning your pond, be sure to adequately budget for the filter system which can be a significant chunk of your total pond and landscape expense. Your pump and filter should be sized to process the entire volume of your pond approximately once each hour.

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In Pond Pump & Filter - This is the cheapest and simplest system. This type of filter ranges from just some foam or filter padding wrapped around the pump to commercial boxes up to a foot or two long. Pumps included with this type of filter tend to be small and only capable of pumping a few hundred gallons per hour. Small in-pond filters are generally best suited to water gardens with only a few goldfish or very small Koi. These filters generally do not keep debris from accumulating on the pond bottom. Cleaning is an unpleasant chore and so tends to be neglected. The advantage of this filter is low cost and simplicity of installation.

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Submerged Pump & External Filter - Moving the filter out of the pond provides many advantages. First, the filter is much easier to clean and will therefore be cleaned more often. You can also accommodate a much larger filter by placing it along side the pond instead of in the pond.

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Pond With External Pump & Filter, Bottom Drain, Skimmer - This pond incorporates several improvements over the previous. A bottom drain will allow debris to be quickly cleaned from the bottom. The surface skimmer will collect debris before it can sink or collect in a crevice. The in-line pump can move more water while using less electricity and it removes the electrical hazard from the pond. Just about any type of filter can be fitted to this pond.

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Pond With Gravity Feed Multi-Stage Filter - The use of a gravity feed settling chamber allows this filter system to efficiently trap most debris. By collecting debris before the water enters the pump, the debris remains in larger pieces which are more easily filtered from the water. Incorporating multiple filter stages allows the use of different media - each tailored to specific tasks. The first stage (vortex) collects large solids. The second stage collects finer solids as well as performing some biofiltration. The third stage is primarily for biofiltration. A staged filter is also easier to clean. The vortex only needs a quick flush to purge accumulated debris. The second stage requires routine rinsing. The third stage should only require seasonal rinsing. The cone shaped chamber is essential for the vortex stage. The remaining chambers may be of any convenient design.

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Pond With Pressurized Filter and Upper Pool - This pond relies on a settling chamber to collect large debris and a pressurized filter for fine mechanical and biological filtering. A pressurized filter allows the use of media that can trap smaller particles. A pressurized filter can also be back flushed to provide more thorough cleaning. A pressurized filter can also be located remotely where it does not impact the landscaping around the pond. Incorporating an upper pool allows plants to be isolated from the Koi resulting in less potting material being dumped out of the pots. The upper pool can also provide a place for quarantine or for performing water changes.

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UV - While not shown in the figures, any of these ponds can be equipped with a UV filter to control floating algae. When installing a UV filter, plumb it with a second pipe in parallel. Put valves on the output of the UV and the parallel pipe. The valves and parallel pipe will allow you to set the flow through the UV for optimum operation without having to reduce the flow through your main filter. The maximum flow through the UV should be around 25GPM for every 40W of UV. You should have around 40W of UV for every 2000 gallons of pond volume.

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