How to Keep Your Koi Fish Pond Clear

One of the most asked questions I get from people who own Koi ponds, is "how to you keep your Koi pond so clear"? The very first thing that I ask them is how many fish do you have in your pond and how what is the size of your pond. Keeping a pond clear is really a many step process. I have listed a few suggestions below.

First you must keep your fish waste to a minimum using the rule of thumb that one 12 inch Koi per 100 gallons of water. Most people always have more fish than their pond can handle waste. The only other way that you can alleviate this problem is to make sure your pond has a bottom drain system. This means your pump is outside of the pond. A good bottom drain system will increase the flow of water which will cycle your water more per hour.

Another important part of the pond system is your filtration. Without good filtration the waste you pick up by your pump can end up right back in your pond. I am an advocate of bigger is better, and that is also true for your pond. Next time you visit your local pond store look at the pond filters; you will see 500, 750, 1000, meaning gallons of water they can handle. Why not purchase a pond filtration system that will handle 500 gallons more than the water in your pond. However, you always want to match your pump to the filter system you buy.

Now I am going to let you in on a little secret. I use a multi-stage filtration system and in the second to last stage I use lava rock. Lava rock is great for filtering out very small particles that may get by your mesh filters, thus making your pond even clearer! But, that is not my secret; my real secret is alfalfa. If you place a tightly woven amount of alfalfa into your Koi pond, you will be amazed of how it reacts to break down waste. I even have a small ball of alfalfa in my filter box.

Using these few ideas above you should be able to maintain a wonderful environment for your Koi fish. Now you know how to keep your Koi pond clean with healthy fish that you can enjoy for many years to come. This is how I learned about pond maintenance from other people who also want to enjoy their garden pond. Feel free to explore my other resources at my website listed below.

Origins and Different Meanings of Koi Fish Types

Koi fish meaning is the thing that people who own and breed koi fish seek because they want to believe that the koi fish means or symbolize something other than just being ornamental fish. They want to believe that caring for a Koi will bring them more than just satisfaction because it can mean something more.

For people who do not know much about the Koi fish, it is nothing but common wild carp with colored mutations. However, for people in the East, specifically in Japan, the Koi is more than just color mutated common carp. The common carp originated in China and was later on brought to different Asian countries such as Japan and Korea, and now they can be found all over the world. Over the years, since the conception of the Koi (more commonly known as the Nishikigoi in Japan), many beliefs, legends and myths have been told to explain the meaning of the Koi or what it represents.

Indeed there have been many stories that have been told about the Koi. According to Japanese myths and beliefs, the Koi can symbolize masculinity, prosperity or good fortune, perseverance during adversity and strength of purpose. In Chinese, a Koi symbolizes balance and harmony (yin and yang), courage and also good luck.

According to the most popular Japanese story about what the Koi fish symbolizes, if a Koi is able to swim up and against the current of a waterfall, at a point called Dragon Gate on a river called the Yellow River, it will transform into a dragon. Thus, explaining why the Koi fish symbolizes perseverance during adversity. The Koi fish is known to swim upstream, like that of the salmon, this perhaps best explains where this most common story about what it symbolizes have come from.

Masculinity is one of the things that a Koi is said to symbolize in Japanese Culture. Every year the Japanese hold an event they call Boys Day Festival where each son in a family participates in the form of a Koi shaped kite. The bigger the kite, the better. The Japanese consider the carp as one of the most energetic fish because it is constantly moving and motion is seen as a characteristic of that of a boy.

In Japanese culture, the Koi fish also symbolizes Family. A specific color represents a member of the family. For example, the black koi is for the father, the flame red koi is for the mother, the blue and white koi represents the son and the pink and red represents the daughter.

The colors of the Koi also have significant meanings. For example, the platinum or silver colored fish represents success in business and the gold koi represents wealth and prosperity.

Many people have taken up collecting different types of Koi as a hobby and most of them believe that the Koi brings good luck and wealth. This can be because a Koi fish can be very expensive, especially the ones that are deemed to be high quality; these kinds of Koi have perfect color markings.

A Koi can mean a lot of different thing but there are really no concrete meanings. All of these are based merely on myths and different beliefs of people. In the end, it is up to the person to decide what the Koi means for him.

What is an Asagi Koi?

The Japanese is one of those famous people when it comes to breeding ornamental fish. Popular fishes that they keep are gold fish, carp, koi, and other tropical fish which are also popular, not only in Japan, but also around the world. The most common and popular is the koi keeping. At this present day, many people already engage their selves in keeping koi. This is also one reason why experts and breeders keep on producing different varieties of koi. They do the crossbreeding method to produce another different variety.

Now, if have you eaten or entered in a Japanese restaurant, you will always see that there are aquariums or ponds with different varieties of koi fish or carps. If they don't have aquariums, they have paintings and pictures of these fishes. Have you ever wonder why they have it? The answer is simple, it adds up to the decoration of the restaurant and at the same time it catches the eyes of the customers because of its beautiful colors. Another important factor why they have this is because they believe that it brings good luck to their business. They have symbolic meaning for this fish -- koi are symbol of love, friendship, and courage.

If you think that keeping koi fish will be easy, then I'm telling you it's somewhat challenging. As mentioned above, it comes in different varieties. Their variety varies with the color that they have in their body. One example is the Asagi koi which comes in blue or blue gray color with red lining on its side, belly and fins. This breed is one of the most common breeds that most keepers have.

Aside from Asagi koi, there are also other koi varieties like the Kohaku (one of the most common), Taisho Sanke, Bekko, Goromo, Matsuba Tancho, and Kawarimono (this breed is known to be unidentifiable when it comes to variety). It doesn't matter what variety you have, what I can assure you is no matter what you have, you will for sure enjoy keeping it. They can serve as your stress reliever.

Koi Pond Algae - How to Prevent Or Remove it For Good!

Before even constructing your garden fond fish, you must come up with a thorough planning and study on how to make adequately a pond and sensibly take care of your koi fish. Consider some points on how to go about some of the important details like how to construct effectively garden koi fish pond, what aquatic plant to grow, how to take care of your koi fish collection and many more.

Let me show you an adequate step on how to deal with in preventing and removing some of the most common concerns of removing koi pond algae. First, focus on the manner on which you construct your koi fish pond. This is very important to detect if your pond is prone to algae growth or not. Though algae normally exist on ponds, it should not be allowed to grow excessively or it will cause immense problems.

Ponds should be constructed in a way that is easy to clean and remove falling debris on sides, top of water and even in depth debris that settled down at the bottom of the pond. To resolve this concern, creating a slope going to one side so that all debris would settle in one place only is appropriate. It creates accessibility and convenience when cleaning. Make variations to the depths of your garden pond fish, perhaps you can have a 35-40% deepest area and another 25 to 30% second level and the rest leaves to the first level. You can have the depth at 1 1/2 to 2 feet.

Second is, try to choose or grow aquatic plants. Algae grows rapidly in waters with high nutrient value. With the presence of aquatic plants and other floating plants like water lilies, lettuce and others you can reduce nutrients. Moreover they can prevent sunlight from penetrating the pond thus reduce growth of algae.

Third, is to clean frequently your koi fish pond especially decaying leaves and debris which highly increases nutrition to algae if not given attention to. Manually remove this debris or use a skimmer in biological pond filters. In order also to minimize falling debris avoid planting trees that excessively gives out excessive debris. However, do not go greedy about not to plant trees near the garden pond. Remember their vital role on giving shelter to your koi and limiting sunlight to your koi fish pond.

Fourth, is to make use of Ultraviolet sterilizers. This is use to damage DNA structure suspended algae which make them clamp together, thus easier to clean. You may use chemical filters in removing it. These UV sterilizers get rid only to those harmful bacteria and micro-organisms making your water crystal clear again. This method is safe and immensely effective, and not to worry because it does not affect string algae in your koi pond.

Fifth, I greatly recommend the use of beneficial bacteria. Regular use can tremendously help in natural algae control which is true to all algae types. Beneficial bacteria can also help reduce water order and improve health of fish. To aid in the growth of this bacterium is by putting in or using rocks and stones as part of your decorative design of your koi pond fish. Having many rocks and stones will definitely aid in the growth of beneficial bacteria.

With these simple ideas I hope it will conspicuously help you in dealing with koi pond algae or better yet prevent rapid growth of algae in your koi fish pond.

Japanese Koi Fish

Koi fish were developed from common carp in ancient China in Jin Dynasty, and were later transferred to Korea and Japan, and are still popular there because they are a symbol of love and friendship. A variety of colors and color patterns have since been developed. Common colors include white, black, red, yellow, blue, and cream. The most popular category of koi is the Gosanke, which is made up of the Kohaku, Taisho Sanshoku, and Showa Sanshoku varieties.

Koi fish make beautiful gifts if you know someone with a Koi pond. Even if they have other Japanese Koi fish the addition would be welcomed. Japanese koi fish are ranked on four factors with the first being the the body shape of the koi is the most important. This helps determine if it will grow to at least 30 inches. The second is its luster and you look for shiny luster over the entire body. The third factor is the depth of colour on the koi, which is referred to as its coat of paint. The last factor you look for is the pattern on the fish. In order to enter your koi fish in competition your koi fish must meet the criteria of patterns to enter. No two are alike which is nice they are almost like a painting each a piece of art.

Japanese koi fish are very expensive so you can imagine the care that goes into taking care of these fish. The process of the Japanese breeding is called the rearing technique. Some techniques have been improved upon in the states even to the point of improving the filtration system which has helped the fish and their health. Since these two areas vary greatly from breeder to breeder in Japan (there are many levels of filtration), the improvements with the breeders in the states are much improved in these two areas that are relative to the degree of sophistication of the particular Japanese breeder. You want to be able to trust your purchase and ensure the quality of the fish. By seeing the enhancements that the breeders have made to improve the living conditions you are more apt to receive a higher quality fish that will be with you for a long time.

Koi Carp Diseases

There are several diseases that Koi fish can suffer from and many of them are related directly to fluctuations in temperatures and extreme weather changes. Koi fish are very susceptible to the cold and tend to fall very ill if exposed to the cold for too long. Broadly speaking Koi Carp disease causes can be classified into five major categories - bacterial, fungal, viral, internal parasites and external parasites. Apart from this there are several environmental factors that can disturb a Koi fish's lifestyle and health like too much exposure to the sun and sub zero temperatures. Koi fish are generally very strong fish and it does not take much effort to keep these fish as pets. Some diseases among Koi fish take care of themselves but others may cause a lot of issues for the fish and can even be fatal.

A disease known as Ichthyophthirius multifilis causes white spot like formations on the body of the fish. This disease is not visible to the naked eye but can be seen clearly under a microscope. This disease usually takes over when the immunity of the fish is weak and the surrounding pond temperature is low. This disease can be fatal but only to smaller fish as the adult fish can fight it off. As far as treatment in concerned, the best way to do away with this disease is to raise the temperature in the pond.

The velvet disease though not very common in Koi can be a source of great discomfort for the fish. It is caused by an external parasite called as Oodinium which basically attaches itself to the outside of the fish ad begins to spread its tentacles until it covers a major part of the skin of the fish. After that it begins to kill off the cells it is nearest to eating away the nutrients from inside. Once that is done, it leaves the fish and begins to multiply, releasing more parasites into the water which have to seek out their own hosts. An entire fish pond can get sick with this type of disease in no time. The most apparent symptom of this kind of disease is a gold dust like formation on the skin of the fish. In many cases this disease causes very tiny puss filled pockets on the skin of the fish that can only be seen through a microscope. These puss pockets cause itchiness and therefore the fish are seen rubbing themselves against objects in the pond.

Koi fish are attacked by worms as well and a very commonly found one is the Lernea elegans which can be a very big problem for the Koi. These worms attach themselves to the belly of the fish and stay there for about a fortnight causing a lot of damage. The worst thing about these worms is that they reproduce rapidly and also leave the fish with bad gashed in the areas they have infected. Fish that are attacked by these worms have to then cope with the wounds on their bodies getting infected by other bacteria and fungi. Once these worms are spotted, immediate action is necessary otherwise the fish will develop multiple problems at one time.

Another type of external parasite are the Argulus lice. They are much easier to spot because of their green color and therefore can be nipped in the bud. The problem with these lice is that they attach themselves to the fins and the sides of the fish and begin sucking out their nutritional needs. While they are attached, the skin of the fish can undergo quite a bit of physical trauma leading to ulceration and infection.

What You Need to Know About Koi Pond Filtration

The filter is the heart of your Koi pond. Koi pond filtration is the single most important function performed in your pond! It is what keeps the water clear and healthy for your fish.
One surefire method for having a Koi pond that fails is to spend all your hard earned money on installing a beautiful pond and then trying to save money on your filter.

A Koi pond filter serves two purposes. First, it serves as a mechanical filter that removes the organic waste produced by your fish along with anything else in the pond that would cloud the water.
Secondly, it serves as a biological filter by converting the ammonia produced by the fish into nitrites and eventually into nitrates which are less harmful to your Koi. Some filters are very high maintenance and require constant attention while others are quite easy to maintain.
The first thing you need to know when it comes to Koi pond filtration is that you can never have too big a filter. When selecting a filter, choosing one that is slightly large for your pond can turn out to be a very wise investment!
For any pond over 1000 gallons it is wise to use a pressurized biological sand or bead filter that can be back washed. There are pros and cons to each.
During the backwash portion of the operation sand, since it is heavier than water, falls to the bottom of the tank instead of flowing out through the valve with the waste. Plastic beads,since they are lighter than water, float to the top. As they are smaller than the valve-strainer's holes, they get washed out through the valve into the waste stream. More and more beads are lost during each backwash operation.
Bead filters also have limited efficiency. Smaller beads have more surface area for good bacteria colonization, but tend to get flushed out during the backwash procedure. This doesn't happen to the larger sized beads, but they have less surface area and thus are unable to filter as efficiently.
By under-loading the sand filters, and backwashing them more frequently with higher pressures and flow rates, you can take advantage of the greater food processing surface areas, while eliminating the chance of plugging. Many manufacturers recommendations for loading sand tend to be too high.
This causes the sand to plug the filter which is the main drawback of sand as a filtration medium.
Up-flow and gravity flow filters need to be cleaned regularly and it is a filthy job. The filter media is packed with rotting organic matter and foul odored fish waste.
As you clean and handle all the various parts of these filters you will find small, white feces-eating worms crawling on your hands and arms. Add to this the ambiance of the offensive odor described above and you don't exactly have nirvana!
The up-flow and gravity flow filters, though inexpensive to make, cost a fortune to purchase. So, in addition to paying a premium price to buy one, you are also spending so much time and labor that you might as well have paid at least twice the price!
If you use a pressurized filter, all it takes is the turn of a handle for 2 to 3 minutes and the filter is clean. Almost like magic! This saves lots of time, inconvenience, labor, mess, and wear and tear on your Koi. It uses slightly more electricity to operate a pressurized pump, but the savings in labor more than make up for it in most pond owner's eyes!
You can also use the waste water for your plants. It is packed with nitrogen and works even better than many of the fertilizers created especially for this purpose!
As you can see,to find the type that is right for you, you have several decisions to make about Koi pond filtration.

Having Your Own Koi Fish Garden

Building and maintaining your own koi pond can be a rewarding experience for those that do it correctly. To add even more enjoyment, you can transform your koi pond into a full fledged koi garden. There are three main parts to a koi garden. They are a Koi Pond, Koi Fish, and Plant life.

A good koi pond will give your fish plenty of room to grow and flourish. A great depth for a koi pond is around four feet deep, because it gives the koi enough room to grow and find protection from predators, such cats, raccoons, and some birds. Also, a larger pond gives you the benefit of adding more Koi later on as you see fit. Koi ponds should be shaded, with very little direct sunlight during the day. Placing a koi pond under a tree is great protection from light and most birds, you will have leaves falling into the pond which can be a nuisance. Also, be wary of lawn chemicals, such as pesticides, as even a little bit can devastate an entire community of koi.

The other part off a koi garden is plants. But sadly, koi fish and plants don't always coexist together successfully. Koi fish are known for knocking over plants, and also digging them up if they are planted in the pond. Koi fish will dig around and actually uproot the plants if they have easy access to them. Adding small pea rock around the base of the plants and then placing several larger rocks on top of the smaller ones will help keep them safe from curious koi fish. Also, closely knitted netting placed around the plants will keep them away safely and effectively.

Taking into account the plants and how you secure them will ensure your newly created koi garden is a success and can be enjoyed for many years.

Black Koi For Contrast

Koi are one of the most prized of pond fish and a large part of the reason for this is the dazzling array of colors and patterns they can appear in. Besides this they are very hardy fish and can be very long-lived. Average life span is around thirty years but a couple are reputed to have lived two-hundred years. Koi fry emerge from the egg around a week after spawning takes place, however color doesn't set until around twelve weeks of age.

The number of patterns and colors Koi can display is confusing at first, yet most come down to some combination of red and white. Black has remained elusive, so the few varieties of koi with black in their coloring have come to be regarded as a separate group known as black koi.

The only variety of koi that appears entirely black is the magoi strain. It is actually a very dark bronze color but seems to be black when viewed from above. Because they are so unusual there is some dispute about whether they should really be counted as koi. They have an extra characteristic that makes them very valuable, however, and that is size. Magoi fish grow bigger than other varieties of koi so there is a trend now to interbreed them with other strains to produce very large fish for big ponds.

One type of black koi which has been around for a long time is the crow, called Karasu in Japanese. It can occasionally have black fins and a black body. More typically only the fins are black, while the body is white or orange.

The most popular black koi variety was only developed around 1980. It is called the dragon, Kumonryu. The main characteristic of these fish is a light body with a jet black pattern on it. This pattern is unstable and can change shape or disappear altogether in response to changing conditions of temperature or other factors in their environment. Sometimes the black coloration can appear totally stable. Other fish can change from one pattern to another in just a few weeks. One weakness this breed displays at times is irregularities in the the tail and pectoral fins.

Another koi variety noted for changing its pattern is the matsukawabake. They are almost always white or light gray, with black areas on the flanks and the top of the body. The edges of these black areas should be wavy to qualify as a true Matsukawabake.

Color is one of the biggest reasons for keeping Koi. The ever-changing swirl of red, white and black can be breathtaking, especially at feeding time when the fish all appear at the same place.

Koi Ponds

A koi pond can be a wonderful landscaping feature capable of turning the average backyard into a relaxing oasis. The possibilities for design are only limited by the amount of available space and the imagination of the homeowner. Items like aquatic plants, waterfalls, and a host of other common pond features can be combined to create a one of a kind, backyard paradise.

Unlike goldfish, koi can grow to be quite large. It is recommended that these fish be kept in groups of at least 3-4, as they don't do as well as solitary creatures. For these two reasons, a koi pond should be much larger than those designed for goldfish. To properly house this species, a pond should be at least 4-5 feet deep, maybe deeper if you live in areas that are prone to harsher winters. Building a pond that is too small is a common mistake that should be avoided.

The location of a koi pond is an important consideration that should be addressed before anything else. These fish generally should not be kept in a pond that is in constant, direct sunlight, as this can be detrimental. Therefore, finding a location with adequate shading is important. If you plan on maintaining aquatic plants as well, this shading should be balanced with enough sunlight for the plants to survive.

When planning a location for a koi pond, eliminating water runoff into the pond is essential. Water runoff from the average backyard will often contain fertilizer chemicals that can do a great deal of damage to your fish. Designing a pond often requires that landscaping modifications be made in order to keep this runoff from affecting the life in your pond.

Maintaining a koi pond often requires pumps and a filtration system. These are designed to reduce common contaminates like algae and bacteria. They also help to aerate the water, ensuring that there is adequate oxygen for both plants and fish. In addition, these pumps are often used to create artificial waterfalls, which add a nice touch to the average pond.

Installing a koi pond in your yard is a great home improvement project that can be done relatively easily. However, it is important to do some research ahead of time to make sure that you have the time and resources to properly build and maintain your pond. Doing so will ensure a lifetime of peaceful serenity.

Seasonal Tips For Feeding Your Koi

Because koi are cold-blooded their metabolism is heavily influenced by the changing of the water temperature during the different seasons. Feeding koi too much food during cold winter months or too little during summer months can become a health hazard. It is vital that you understand how the temperature will affect the koi so you can adjust your feedings accordingly.

A pond thermometer is a great way to provide accurate readings of your pond water throughout the year. Because of the changes in the metabolism of your koi their digestion will become very slow during very cold months, when they produce little if any enzymes that enable them to digest their food. During warmer temperatures their metabolism speeds up, activity increases and growth occurs. This is when they will require daily feedings.

Each season also requires a different type of food. It is important to adjust the protein and carbohydrate content of their diet as well as the amount of food they eat. Some koi are more active than others so you will have to adjust the type of food and the amount of food to your particular type of koi. Another consideration is will be for koi that are smaller and still growing verses koi that has reached their maximum growth potential.

Summer Koi Feedings

During summer months when water temperatures are at their warmest, your koi will be very active. This is a time when they have the most potential for growth. It is also a time when they will need to be gaining some extra weight for the winter months when feeding is minimal.

Feeding your koi very small meals throughout the day will produce better results than feeding one big daily meal. Feeding small meals several times daily will help in the taming of your koi to eat right from your palms. Another benefit of taming your koi is the ability for you to check them over and if needed remove them from the pond should they become unhealthy and need some type of treatment or quarantine.

Spring Koi Feedings

During spring when the water temperatures are between 45° and 55°F koi do well on a low-protein diet because their digestive enzymes are not at their optimum. As temperatures raise from winter, their metabolism increases, however, it is not an instant change. If your koi have not been eating for weeks or very little food, you will need to slowly increase their food. Feeding too much too fast can create digestion problems. Vegetable-based food with protein are the most common foods offered during the time when they have a slower metabolism.

Feeding Koi During Winter Months

When the temperatures drops below . One way is to take your koi out of your pond and bring them into the garage or someplace where the water temperatures will not be dropping so low it could cause problems. The other way to help your koi cope is to stop feeding them altogether or to feed very minimally.

Rather than stating a set rule here it is best for you to talk to your koi dealer as to the type of koi you have and their feeding and wintering needs. Some koi require more oxygen then others as well as other differences that should be individually addressed.

Bad Feeding Habits for Koi

Some people enjoy feeding their koi fresh foods like sweet corn, peas, lettuce and brown bread. While these items may be ok from time to time, they can become a problem as they do not provide a balanced diet and in some cases can be very hard to digest. In addition, these types of food meals can create excessive waste and create cloudy water in your pond.

If your pond is adequately filtered with the water quality being stable, feeding your koi little treats such as those listed above should not prove to be a problem. One way to overcome the excessive waste would be to make sure the excess food is removed from the pond before it can rot and making these sorts of meals more as rare occasional treats presented during active summer months when koi digestion is at it's peek.

Maintaining a good habitual watch on your pond water temperature will insure proper food adjustments as temperatures change from one season to the next. Help your koi live a long and healthy life by educating yourself and learning from others rather than learning painful lessons from inexperience and a lack of proper education.

Maintaining the Health of Your Koi

When you built your pond, you probably spent a lot of time planning its design. You made sure every plumbing piece was in place. You carefully selected your filter and your pump. Everything seems perfect. While everything mechanical is in place, did you know that you need to plan your fish just as carefully as everything else?

Many experienced fish keepers will tell you that the best way to guarantee long-lived healthy fish is to buy top quality stock from local reputable breeders. This ensures you have fish that have not been overly stressed by transport, carefully bred for quality and grown on the best food.

If you aren't lucky enough to have a local koi breeder, or you've already bought your koi, not all is lost! In fact, most purchased koi are from national-level breeders, have been transported and do not have confirmed breeding standards. This doesn't mean you can't have great fish. It just means you need to be extra careful to quarantine and feed high quality food for continued growth.

Quarantining your koi fish is absolutely necessary for koi health. Every time you obtain a new fish (regardless of source), you need to quarantine your new koi for at least 4 weeks before adding it to your existing stock. If you don't properly quarantine, you risk introducing foreign bacteria and viruses into your stock. There are some fish illnesses, such as bacterial infections, flukes and worms that can kill your stock in one week after introduction.

Proper quarantine means no mixed water, food or contact between your existing stock and your new fish. When quarantining, you need to watch out for signs of stress in your new fish. Signs of stress and illness include a lack of appetite, discoloration on the scales/eyes, torn fins and lethargy. If you notice any such signs, there are several treatment options.

If your fish has torn fins or external lesions, you should treat with antibiotics administered with the fish food. If your fish isn't eating after several days, you may have internal parasites. Praziquantel (a.k.a. PraziPro) or metronidazole are very effective safe treatments for internal parasites, including gill flukes and worms. We recommend NOT using Potassium Permanganate unless you have exhausted all other options. Potassium Permanganate should never be used on fish with external lesions as it will burn their internal tissues.

After you've quarantined your new koi, and all goes well, you can add them to your pond! Depending on your bio-load and the number of fish you add, you may need to up your water changes. Already you should be changing at least 30% of your pond water a week to keep your pH stable and nitrates low. Adding more fish adds more waste to your filter, and it may take some time for new nitrifying bacteria to build up. Water changes keeps nitrites low if you've recently added a lot of new fish.

On top of water changes, you should regularly add salt to your pond. This isn't table salt or anything like that. We're talking about salt that's iodine-free and designed for aquarium and pond use. When you add salt to your pond, your koi will build up a thicker slime coat that supports a strong immune system. Pond salt also helps respiration in koi, and is effective in killing many common parasites. You should add 2 - 2.5 cups of pond salt per 100 gallons. You should only add more salt when you perform a water change (it does not evaporate).

For your koi, you should vary their diet instead of feeding the same pellet every day. This ensures they get enough nutrients from a variety of sources. If you have very young koi, it doesn't hurt to feed them a hearty supply of beefheart so they grow well. Also, it's okay and encouraged for your koi to eat some plants. This gives them plant fiber which helps prevent bloat.