Koi Pond Design

It's important to share knowledge and resources in order to make educated decisions in the design, construction, and ongoing maintenance of your koi pond.  

We link to many different resources to provide informative articles and share experiences.  There are many different opinions out there too but generally all koi keepers have the same goals.

When we design and build a koi pond, we consider each site individually, as well as the budget.  So just keep in mind that what makes the perfect pond for someone else may not be the best for your individual application.



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Many thanks to Sacramento Koi for the following information on designing and building Koi ponds.


Koi Pond Design Koi Health Koi Water QualityKoi Parasites Koi Bacterial Infections


No matter how beautiful a koi pond is, if the basics for a successful koi pond are not incorporated during the construction of the pond the owner will never be satisfied with it. Koi ponds are unique to themselves. The requirements for a successful water garden or even a gold fish pond are minimal. On the other hand, because koi fish are fast growing, produce a lot of waste and need very good water quality to flourish, they require a very special pond. A successful koi pond will address these issues, but at the same time it should be as easy as possible to maintain. The following information is provided to help you plan your “Perfect Pond”.

Topics (clicking a topic will take you to that section)

1) How large should I make my pond?
2) Where should I place my pond?
3) Can I grow plants in my pond?
4) Which pond is better, a rubber liner pond or a concrete pond?
5) How important is the shape and contour of the pond?
6) How deep should I make the pond?
7) How important is the filter?
8) How far away from my pond can I install my filter system?
9) Do I need a pre filter?
10) What size pump will I need?
11) What size pipe should I use?
12) How important is it to have a bottom drain?
13) How important is it to have a skimmer?
14) How important is it to have jets?
15) How important is it to have an auto-fill?
16) Do I need to install an ultraviolet light?
17) Should I install under water lights in my pond?
18) Should I install an automatic feeder on my koi pond?

19) How many koi can I put in my pond?
20) What should I look for when selection someone to build my koi pond?
23) The “Advantage Koi Pond Design Plans” for 1,500 to 15,000 Gallon Ponds.

1) How large should I make my pond?  One of the most common mistakes people make with their first pond is that they build it too small. For koi fish, the smallest pond we recommend building is 1500 gallons, which would be approximately 7 feet wide by 8 feet long and 4 feet deep. That may sound huge to many beginners, but most people who already have a koi pond, will agree that if you build a pond much smaller than that, you will not be happy with it. The problem is that koi fish are extremely addictive and it is hard to be content with just a few. Also, keep in mind that you may start out with several 6 inch long koi, but within 3 or 4 years they could grow to 24 inches or more. With few exceptions, most people, after a while, wish they had made their first pond bigger. On the other hand, you can also make your pond too big. Bigger is not always better. The largest pond we recommend building is 15,000 gallons, which would be approximately 17 feet wide by 21 feet long and 6 feet deep. If you build a pond much larger than that you run into several problems. In a very large pond it can become almost impossible to catch the fish if you need to. It can also be very expensive to medicate the pond if that becomes necessary. Additionally, all the water in the pond will need to be filtered at least once every three hours. Running pumps large enough to accomplish this can cost several hundreds of dollars per month. Finally, if you build the pond too large you may not enjoy the koi as much, because in a very large pond the koi are not always visible.

2)  Where should I place my pond?  There are several things to consider. First, koi ponds do better in a shaded area than in full sun. Full sun will work, but a shaded area will generally slow the algae growth down and will prevent the water from possibly getting too hot during the summer months.  If you chose to build in a sunny area it might be practical to think of building some type of arbor, either now or in the future, to give your pond some shade. Unlike a swimming pool, leaves from trees near the pond should not create a problem if the pond is properly designed.*  In many areas local building codes require any pond deeper than 2 feet be within a fenced in area, which could present a problem if you want to build it in your front yard. Once you have chosen a general location for the pond, we recommend you use a garden hose to outline the exact location, size and shape of the pond. This can be extremely helpful in giving you a better idea of exactly how the pond will look. After placing the hose where you plan to build the pond, stand back and examine it from several locations and ask yourself. “Will it be the size pond that I want”? “Will it be as visible as I would like it to be from, say, the back deck, the kitchen window or wherever I would like to be able to see it”?  Keep in mind, this pond will most likely be the central feature of your whole landscaping. Once you have the general outline shape of the pond established you can get a approximate idea of how many gallons it would be by multiplying the (average length) x (average width) x (average depth) x (7.5 gallons per cubic foot). 

*One note of caution: Pine trees are the one exception. Pine needles tend to create a real mess in a koi pond. Unlike leaves, needles can travel through the skimmer basket and the leaf basket on the pump and end up in your pump impeller. If possible, do not build a koi pond near a pine tree. Redwood trees, although messy, are not near the problem pine trees are.

3)  Can I grow plants in my pond?  If you really want to grow plants in your koi pond you can, but they really complicate things. Here is why:

  • If you place shelves in the pond to support the plants and the shelves are less than 2 feet deep, you risk the chance of loosing your koi to predators. Even if the shelves are deeper than 2 feet below the water level you may still have a problem.  If when you place a potted plant on the shelf and the top of the pot is less than 2 feet from the pond surface a blue heroin may wait until a fish swims over the pot and then strike, pinning the fish against the plant pot.

  • Most water plants do not like water movement so you cannot use jets in the pond. Therefore,  most of the leaves that fall in the pond will sink to the bottom before they reach the skimmer and may have to be netted out by hand.

  • Often times new plants will have parasites on them so you will need to treat them with  potassium permanganate before you introduce them to the pond.

  •  If parasites do get into your pond you will need to treat the whole pond. Most chemicals used to treat for parasites in koi ponds are toxic to plants. This means you will need to remove all the plants while you treat the pond. Additionally, you will need to treat the plants separately before you return them to the pond.

  • One of the most effective ways to combat string algae in a koi pond is to increase the salt level in the pond to .4%. This is not an option when you have plants in the pond because, most plants cannot tolerate salt and will die.

  • Once koi get to be 12 inches or larger they begin to eat most plants.

  • Most pond plants begin to die back in the fall and create a real mess in the pond.

  • Koi can hide under the pond plants and this can create a potential problem. If a koi gets sick and begins to isolate itself, you may not notice it until it is too late. Plus, if you need to catch a koi for any reason it can be a real challenge catching them among all the plants

Some people will argue that you must have plants in the pond because the plants are necessary to consume the nitrates that build up in the pond. That would be true if it weren’t for all the algae that naturally forms in a pond. A healthy pond will normally develop a ¾ inch layer of green algae on all the inside walls of the pond. This algae, which feeds on nitrates just like pond plants do, is usually more than sufficient to keep the nitrates at a safe level.

A pond with plants in it can be very attractive, but so can a well landscaped pond which has beautiful plants surrounding it, yet with none actually in the pond. Tom Holder (owner of Koi Care Kennel) built this pond with the Advantage System on it and with no plants in the pond. He has a healthy pond that is both beautiful and very easy to maintain.

4)  Which pond is better, a rubber liner pond or a concrete pond? They both have their own advantages. A concrete pond, when designed and built properly, is more permanent. ( You must make sure it is designed and plumbed properly because it is almost impossible to make changes later.) The shape and contours can be very smooth and even. The biggest disadvantage of a concrete pond is that because of all the exposed concrete the ph tends to be higher than ideal for at least the first three years. This can easily be overcome by letting the concrete cure and then coating the pond surface up to the water line with a rubber base paint or epoxy. A 45 mil rubber liner pond  is not as permanent, which can actually be a benefit. If the pond has some design flaws that you need to change or you need to remove the pond, a rubber liner is much easier to work with. A real advantage is that liner ponds tend to maintain a more neutral ph. The rubber liner creates a very soft surface for the koi. Even when a liner pond is installed properly you will have a number of miner folds in the liner. Once the pond is filled with water these folds become barely visible.  Rock work around the edge of a liner pond can be a challenge if you don’t want the liner to show. The reason is because the rock work will need to extend down into the water and the mortar for the rock work will not stick to the liner. ( To solve this problem see “Advantage Pond Design Plans” under “Rock Work”.) The problem of cutting a hole in a liner for the bottom drains, jets, etc. is easily overcome with the proper drains and bulkhead fittings. When installed properly a liner pond can easily be leak free for many years.

5) How important is the shape and bottom contour of the pond? The shape of the pond is much more important than most people realize. Many times people will get very creative with the pond shape so that it rambles all around the landscape and ends up looking like a piece of a puzzle. Only after the pond is built and filled with water dose the problem become apparent. You can’t keep it clean. If the pond is shaped so that it has dead areas where the water is not moving, leaves and debris will collect there and eventually sink. Additionally, the bottom contour of the pond is equally important. Flat bottom ponds require constant vacuuming to keep them clean. If you are retired and have two hours each day to clean your pond you can build it any shape you wish. On the other hand, if you want to build a pond that is almost “self cleaning” pay close attention to both the shape of the pond and the inside contour leading from the edges of the pond all the way to the bottom drains. We can’t express enough how important the contour of a koi pond is. A well designed pond shape and contour can save you many hours of back breaking work and help provide a healthier environment for the koi. See the “Advantage Koi Pond Plans” for more details on pond shape and bottom contour.

6) How deep should I make the pond? A serious koi pond should be at least 3 feet deep and no areas should be shallower than 2 feet. Any areas shallower than 2 feet is an open invitation to dinner for both blue herons and raccoons. If you don’t think you have predators in your neighborhood just build a shallow pond and watch what happens! Even a single safety step to help you get out of the pond, that is less than 2 feet deep, can cost you most of your fish. Also, all sides should go almost straight down, not tapered. “Aquascape” type ponds where the sides of the pond gently taper in toward the bottom will not work for koi. Even if you build a “deep area” for the fish with a cave in it, for them to hide in, you are still not safe. Blue herons will wade out into the water, stand perfectly still, and simply wait for the koi to come out and then strike. Do not place shelves for plants in the pond. You can hang potted plants over the side with wires to support them. That way if you start having problems you can simply remove them. If you decide to ignore this advice you will probably ( after loosing your favorite fish) end up covering your pond with a net or in one case I saw ½ inch rebar used to keep out raccoons. Most people would agree that a beautiful pond is somewhat ruined when it has to be covered with something to protect the fish. A deep pond with steep sides is the best defense against predators. Koi fish get their exercise by swimming up and down in a pond rather than horizontally. Therefore, if you plan on growing “jumbo koi” you will need to build the pond at least 6 feet deep.

7) How important is the filter? The filter is the heart of your koi pond. The filter is what keeps the water clear and healthy for the fish. Many ponds have failed because the owners spent all their money on a beautiful pond and tried to save money on their filter. The filter serves two purposes. One, it serves as a mechanical filter removing fish waste and anything else in the pond that would cloud the water. Two, it serves as a biological filter by converting the ammonia produced by the fish into nitrites and eventually into nitrates which, in general, are harmless to the fish. Some filters can be very high maintenance requiring constant attention while others can be very easy to maintain. Rule number one, when it comes to filters, “You can never have too big a filter.” When choosing a filter, selecting a filter that is slightly oversized for your pond can be a very wise investment

8)  How far away from the pond can I install the filter system?   The Advantage Bead Filters have the advantage of being a pressurized system. That means the filters can be installed some distance from the pond making it easier to hide. For long runs from 50 feet to 300 feet, the diameter size of the pipe traveling to and from the filter may need to be increased, up to 3 inches, depending on the size of the pond.

9) Do I need a pre-filter?  A pre filter is designed to collect solid material such as leaves, fish waste and string algae before they get to your filter. In some small ponds, the pump and skimmer baskets may be sufficient. The larger the pond, the more debris it will produce, therefore, the more important they become. Pre filters are especially important if you have a filter that is hard to clean such as a gravel type filter, because you usually are only cleaning them once or twice a year. The more waste you can keep out of them, the less often you will have to clean them. Pre filters are not as important with a good bead filter because you can easily remove the waste from the filter whenever necessary.

     There are basically 3 types of pre filters:

  • A simple holding tank, made of concrete or fiberglass, with rows of brushes or mat material suspended in it to capture debris before it gets to the pump. A typical tank  may be 5 feet square and 2 to 3 feet deep. This type of pre filter will require you to regularly remove and clean the brushes or mat material

  • Vortex pre filters are shaped like a big round tub that is tapered at the bottom. Water enters from the side at an angel which causes the water to rotate in the tub. This causes any debris to drift to the outer wall and then sink to the bottom of the tank where it can be drained out when needed. Clean water exits from a pipe in the center. Vortex filters may require a large hole to set in and in some situations, a sump pump to drain them. 

  • The “Advantage Collector Box” is a fiberglass box with a large rigid net in it. The large model has 4 openings, each with a slide valve that allow you to select up to 4 different sources from where the water is to be drawn from. The medium model has 3 openings. With the valves you can easily regulate the flow from each source and on occasion, flush one line at a time to reduce the chance of debris collecting in the pipes. It requires the least amount of space and is probably the easiest to clean. It is designed for ponds 6,000 gallons and larger.

10) What size pump will I need?   In selecting a pump you have one simple goal in mind. To move the proper amount of water for the least amount of money. The hard part is to estimate how much water you need to move. Here are some things to consider. Ideally, you want to send all your pond water through the filter at least once every 2 to 3 hours. We also recommend sending water through some jets on the sides of your pond. (see #14 How important is it to have jets?). Are you going to have a water fall? If so, how high will it be? What kind of filter will you be using? Is it important that the pump be quiet? All these factors have to be considered before you select a pump. Make sure you purchase an efficient pump built for koi ponds. Your pump will be running 24 hours a day. An inefficient pool type pump can cost you an extra $100.00 a month in electricity.

11) What size pipe should I use?  Pipe size is extremely important on koi ponds. Pool builders will often use smaller diameter pipe when building a swimming pool because it is cheaper and easier to work with. They can easily overcome the restriction caused by the smaller pipe by using large high pressure pool pumps. This is acceptable because they usually only run these pumps 4 to 6 hours a day. Koi ponds, on the other hand, must move large volumes of water 24 hours a day. The smaller you make your pipe, the more pressure it will require to move water through it. Pumps are rated by how much water ( gallons per minute) they can move at a certain amount of head pressure. 1 foot of head pressure is the amount of pressure required to push water up vertically 1 foot. Example: To move 20 gallons of water per minute through 50 feet of 1 inch pipe would require 11.4 feet of head pressure. If you increased your pipe size from 1 inch to 2 inch your head pressure would drop to .4 feet of head. The lower you keep your head pressure, the smaller, more efficient pump you can use. This can save you a lot of money over the years.

12) How important is it to have a bottom drain?   Another common mistake that is almost impossible to correct after the pond is built is failure to install a bottom drain. Bottom drains are a must for a successful koi pond. To maintain proper water quality you need to get the fish waste into the filter so it can be removed from the system. Without a bottom drain, the best filter in the world cannot do it’s job properly. Some ponds may require several bottom drains. That shows how important they are to a successful pond. Some manufacturers would have you believe that a bottom drain is not required. By simply placing rocks on the bottom of the pond and allow beneficial bacteria to grow in the rocks you will duplicate what you find in nature and everything will be just fine. The problem with that reasoning is that in nature you often have a constant supply of fresh water entering the river or lake and the fish population is usually about one fish per 30,000 gallons whereas, in a koi pond you are constantly recycling the same water over and over again and the fish population averages about one fish per 150 gallons. Unless you only put one koi in your pond and change the water constantly you can’t duplicate nature. What works in nature will not work in a koi pond. Also, as leaves collect and begin to decay amongst the rocks, they produce tannin acid which, though it doesn't bother the fish, will turn the water a brown dirty looking root beer color. The only way to get clear water again is to drain the pond and power wash the rotting leaves from between the rocks. This is a major job which, at best, provides only a temporary fix until the leaves again collect in the rocks. Additionally, this whole cleaning process is extremely stressful to any koi in the pond since they will need to be netted up and stored while the pond is cleaned and will then be placed back into a pond that has experienced a 100% water change and the whole ecological balance of the pond has been changed. This whole experience can be avoided by simply leaving out the rocks, installing a bottom drain and contouring the bottom, so that any fish waste or leaves that end up on the bottom of the pond will work their way to the drain and be removed. 

13) How important is it to have a skimmer? A skimmer can make the difference between enjoying a pond and beginning to resent it after a while. A properly functioning skimmer will collect the leaves and anything else that lands on the surface of your pond into a net or basket, where it can be easily disposed of. Without a skimmer, you are sentenced to a life of constantly cleaning leaves and debris from your pond. They are a real bargain when you consider the minimal expense they add to your pond. Note: Even if you plan to build your pond inside your house, where there would be no leaves, you should still install a skimmer because in addition to leaves, they skim off the “dissolved organic compounds” (DOC). Dissolved organic compounds will form in any pond and if not removed will causes an unsightly film and bubbles on the surface of the pond. A skimmer removes this film by constantly skimming off the top surface of the pond.

14) How important is it to have jets?   Jets are very often overlooked by beginners when building a pond. Anyone who has ever had properly installed jets in their pond would never consider building a pond without them. Jets have several wonderful benefits. They provide exercise for the fish because they love to swim in the current. By installing the proper type of jets, in the right location and depth in a pond, they can be used to direct leaves toward the skimmer making the skimmer much more effective. In addition, as the water from the jets breaks the surface of the pond it picks up considerable amounts of oxygen thus increasing the overall oxygen level of the pond.


15) How important is it to have an auto-fill?  An auto-fill is one of those features that if you install one you will love it. It makes maintaining a pond much easier. An auto-fill does just what the name implies. It will automatically keep the pond water at the same level all the time. As water evaporates, it will automatically replace it. They are especially useful if you have a bead filter, because each time you backwash the filter the auto fill will replace any water used during the process. Too often you hear of someone turning on the hose to add water and then forgetting to turn it off only to later find all their koi dead. This is because whenever you replace more than 10% of your pond water at any one time, with city water, you need to add a dechlorinater to neutralize the chlorine in the water which is toxic to fish. With an auto-fill you don’t run the risk of forgetting to turn off the water. Under normal use it is generally not necessary to add dechlorinator to the pond each time the auto-fill comes on because it is only replacing such a small percentage of water. Again, the exception would be if you were replacing more than 10% of the pond water at any one time.

16) Do I need to install an ultraviolet light?  New ponds are especially prone to algae blooms until the whole ecological system of the pond matures which may take several years. Ultraviolet lights are designed to kill any algae floating in the water. Algae blooms in ponds can turn a perfectly clear pond into a thick pea soup looking pond in a short period of time. The way ultraviolet lights work is when the algae in the water passes through the unit it is exposed to a very bright ultraviolet light. This energy from the light destroys the DNA in the algae which in turn causes it to eventually die. As the algae cells die they will begin to stick together so that they can be filtered out of the water. Selecting the proper size light is very important. If the light is not big enough for the pond that it is installed on you will notice almost no effect. Additionally, if the water flow through the light is too fast it will also reduce the efficiency of the light to where it has little effect. Ultraviolet lights are not effective against string type algae because it attaches to the pond and does not flow through the light.

17)  Should I install under water lights in my pond?  Under water lights installed in a pond extends the enjoyment of the pond beyond the daylight hours. The pond takes on a completely different look at night with lights in it. At night, because there is no glare from sunlight on the pond surface, the koi become more visible than ever. The only complaints we ever hear about pond lights is that “I wish we had installed more lights when we built the pond”. We usually recommend installing several or more lights in a pond, depending on the size of the pond. Generally, the purpose of adding lights to a koi pond is to light up the koi not just the pond When you only add one light to a pond you often times end up with one stream of light shining across the pond while much of the pond is still in the shadows. With several lights coming from different angles the whole pond lights up and thus the koi become very visible.

18)  Should I install an automatic feeder on my koi pond?  Automatic feeders have their place. If you have a large pond and you want your koi to grow as fast as possible, then install an automatic feeder and feed them a high protein food 5 times a day during the whole summer. On the other hand, if you just want something to relieve you of the responsibility of feeding your koi daily I would encourage you to save your money and find the time to do it yourself even if it is only once a day. By feeding your koi on a daily basis you will become familiar with how they respond to the food. This is invaluable! The first time you feed them and you notice one or more of them responding differently, you know something is wrong. It could be something as simple as your water chemistry is off or something more serious such as parasites. Whatever it is, you will be able to get a jump on it before it becomes a real problem. When you go on vacation just ask your neighbor if he or she would mind coming over once a day and throwing some food in the pond. Most neighbors would jump at the chance. The real advantage of your neighbor feeding you koi while you are on vacation rather than some machine, is that if there is a problem they can call someone.

19)  How many koi can I put in my pond?  This is a good question and a hard one to answer. There is an optimum number of koi for each pond. The problem is, that number keeps changing. A well built 1500 gallon pond will easily sustain 30 koi 6 inches long. Two years later when those same 30 koi are now all 18 inches long you have a real problem, because your pond is now over stocked. Because people tend to overstock their ponds, all the Advantage Koi Pond System Kits, were designed to have an oversized filter on them. This means that the limiting factor for how many koi you can keep in your pond will not be limited by the filtering system.  Rather, the limiting factor will be how crowded the koi look in the pond. Even with perfect water quality when the koi become too crowded their immune system begins to slow down and they begin to have problems. The best way to judge how many koi to keep in a pond with the Advantage System is simply to examine how crowded they look.  If they can’t swim in a relaxed fashion it is time to remove some even though the water quality tests fine.

20) What should I look for when selecting someone to build my koi pond?  Do not make the costly mistake of assuming that your landscaper or contractor knows how to build a koi pond correctly. You need to do your homework and give some serious thought as to how you want your koi pond to turn out. Review the previous questions and make notes as to what is important to you and what is not. How big do you want the pond to be? How important is it to you that the pond be easy to maintain? How much do you want to spend on the pond? You need to have clear in your mind what kind of pond you want. Then, when selecting someone to build your pond, interview them concerning their workmanship and experience. If you can find someone who specializes in building koi ponds, that might be helpful. The reason I say it might be helpful is because sometimes people who only build koi ponds have one set way of building them and are not open to changes. With today’s new technology you can create a pond that will not only give you better water quality, but one that will be so much easier to maintain than what was offered just 8 years ago. Unless you and your builder can agree, beforehand, on exactly how you want your pond to be built, the whole experience could be a disaster. For example: One customer contracted to have a formal shaped 3,000 gallon pond built “exactly” according to the “Advantage Koi Pond Design Plans” for a 3,000 gallon pond. He was a very busy doctor who needed a pond that was as easy to maintain as possible. The contractor continued to assure him, as he was building the pond, that he was following the plans exactly. When the pond was finally completed it was beautiful to look at with it’s slate waterfall and edges. At night, the lights he installed help create a wonderful sight. The problem was that there was no gradual contour leading from the sides of the pond to the bottom drain. The contractor had completely ignored the recommended bottom contour so the waste would be removed automatically and instead made the whole bottom flat. The result is that, now the owner has to, on a weekly basis, vacuum the bottom of his pond to keep it free of debris. Needless to say, the owner is furious with the contractor. The lesson from this example is that you really need to get involved in the design of your pond. Don’t leave it all up to your contractor. Listen to his advice but it is up to you to make sure it is being built correctly. If you need a second opinion, feel free to give us a call at Sacramento Koi.


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