Category Archives: Koi and Ponds

Ochiba Shigure – Autumn Leaves on Water by Bryan Bateman

Have you ever seen a soft gray colored koi with gold patterning? If you have, you likely would not forget, because it is very different looking than the brightly colored koi we are used to seeing. This quietly refined and elegant koi is called an Ochiba Shigure, which aptly translates to “autumn leaves on water”. The delicately reticulated scales do indeed give an impression of leaves floating on a calm pond, with the golden-leaved trees reflected on the surface.

Ginrin Ochiba

Ginrin Ochiba

nordic 53cm ochiba

nordic 53cm ochiba

A relative newcomer on the koi scene, having been around only since about the mid-90s, the Ochiba is actually a cross between a gray Soragoi and a golden brown chagoi. These two ancestors have a reputation of being the friendliest of koi, and the Ochiba has happily inherited that trait. Many hobbyists will have one of these types koi in their collection for the purpose of encouraging other, shyer koi to “come out of their shells” and be more sociable. They will be the first to come up to greet you as you approach your pond, and will readily eat from your hand.

For show purposes, they are usually grouped with the “kawarimono” class, which is a catch-all for many of the lesser-known varieties. However, due to their increasing popularity, some shows have a special award for best Ochiba. There are many newer types of Ochiba as well, including a scale-less Doitsu Ochiba, a sparkling ginrin Ochiba, and most recently a metallic doitsu ochiba. Another sub-variety has been a cross between a red and white Kohaku and an Ochiba, giving an attractive gray and red patterned koi.

If you want a friendly new addition to your pond, and you enjoy the understated softness of earth tones that remind one of the colors of fall, Ochiba Shigure might be your koi.

© Bryan Bateman 2009

Ginrin – Diamonds by Bryan Bateman

Many of us when new to the koi hobby are attracted by those “sparkly” little koi that seem to be covered with diamonds. These are known as “ginrin” koi. GinRin is not a variety per se, but a characteristic that can be seen on any scaled koi. The Japanese pronunciation sounds like “geenleen”, but it has been Americanized by most to sound just like it looks, with a hard ‘G’. It translates to “silver scale”, and is sometimes referred to as “KinGinRin”, or “Gold and silver scale”. This is because, when ginrin appears on a red fish such as a kohaku, it sometimes has a gold appearance. This silver effect is due to the presence in the scale of a chromatophore called guanine, which was first noticed in a random spawning in Japan in 1929.

Ginrin Kohaku

Ginrin Kohaku

Ginrin Showa

Ginrin Showa

Ginrin Ochiba

Ginrin Ochiba

There are actually four distinct types of GinRin scales. The most common is known as “diamond gin”, and appears much like cracked glass over the entire scale. A highly valued type, and hard to find in this country, is called “Beta Gin”, which is characterized by the entire scale being covered with silver, much like a mirror. A third type is “kada gin”, or “edge gin”, which is exactly as it sounds – each scale is edged in silver. The last, and by far rarest, is pearl gin. On this type, the gin appears only in the center of the scale, and truly looks as though someone carefully mounted a diamond on each scale.

When selecting a young ginrin koi, look for those with at least three rows of ginrin scales on either side of the dorsal fin. These scales should be evenly lined up in neat rows and of consistent shine. I can remember when I was new to the hobby and looking at a young ginrin with jumbled ginrin scales. The dealer told me not to worry, that they will line up as the fish grows. Didn’t happen, and never will!

Appreciation of ginrin can be a very personal and subjective point. Some hobbyists feel that it is a distraction, particularly in patterned koi. It can certainly be a beautiful enhancement to one-colored koi such as cha-goi and yamabuki ogon. Whatever your preferences, any collection will benefit from the presence of one or more of these “living jewels.”

© Bryan Bateman 2012

Tancho – The Crane by Bryan Bateman

A tancho is any koi with red located only on the head. If it has red anywhere on the body other than the head, it is no longer considered a tancho. Named for the Tancho Crane, and very popular in Japan due to the similarity of this type of marking to the Japanese flag, tanchos have their own class in koi shows. This class generally includes tancho kohaku, tancho sanke, and tancho showa, but may include other types of tancho as well, such as tancho goshiki, tancho beni kumonryu, or tancho ochiba. The inclusion of these other types of tancho is determined by each club and show chairman.

Tancho Goshiki

Tancho Goshiki

Tancho Kohaku

Tancho Kohaku

Tancho Showa

Tancho Showa

The tancho marking may have many shapes, however a round shape is considered ideal. The size of this mark should be as large as possible without going past the eyes, back onto the beginning of the scales, or too far forward on the forehead, and it should be centered. Other shapes sometimes seen are square, cross-shaped, or irregular flowery-type shapes. Any of these are acceptable on a tancho as long as they are uniformly shaped, are centered on the head, and have a pleasing look to the eye.

Purchasing a young tancho can be risky as they frequently will lose the tancho mark as they mature. It is best to buy them at two or three years of age, as the mark will generally be stable by this time. You want to look for a tancho marking that appears thick, with no windows or light areas, and with clean, sharp edges. In the case of tancho sanke or tancho showa, look for a pleasing, well-balanced sumi (black) placement to complement the red marking. My favorite is tancho showa, especially the ones with black partially covering the tancho mark – giving the appearance of clouds passing in front of a full harvest moon.

© Bryan Bateman 2012

Yamabuki Ogon by Bryan Bateman



Yamabuki Ogon
 

The history of the development of metallic koi is an interesting one. About 90 years ago, a Japanese hobbyist by the name of Sawata Aoki had a dream to create a special type of koi. When he heard that a young boy had found a wild carp in a river which had golden stripes on it, he walked many miles to see this carp, and convinced the boy to sell it to him. He carried his new treasure home and spent the next 25 years patiently breeding and selecting the brightest and shiniest offspring until, in 1946, he finally achieved his dream – the first metallic koi. This koi soon came to be called a Yamabuki Ogon, and is the original ancestor of all metallic koi that we have available to us today.

 

Today Yamabuki Ogons are one of the most popular of varieties. Although extremely expensive when first made available to Japanese collectors, they can now be had at prices well within the budget of most hobbyists. They are hardy, grow quite large, and are generally the friendliest of koi. Their bright shiny yellow color will attract your eye especially as the sun strikes them.


When selecting young Yamabuki Ogons, look first for a healthy, energetic koi with a solid body shape (not too skinny or too fat). Next in importance is the sheen. Look at the pectoral fins, along the back, and on the head. These areas should be highly reflective as the light hits them. The head should be “clean” – no dark smudges or spots of orange or red. The color can range from a pale to a darker yellow color. Generally as they grow the shade will darken somewhat. Look closely at the scales to make sure there are no orange spots or scales that are out of alignment – the color should be even and the scales arranged in neat rows front to back.

© Bryan Bateman 2014

The Elusive Beni Kujaku by Bryan Bateman

One of the more interesting and attractive developments in recent years has been the modification and improvement of a popular variety known as the Kujaku (“peacock” in Japanese) The first Kujaku was created in 1960 by crossing a matsuba ogon and a hariwaki. The result was a metallic koi with reticulated scales and a pattern of yellow, orange, or various shades of red on a white background. The Kujaku became an instant hit with collectors. For show purposes, Kujaku is placed in the Hikarimoyo class, competing against other patterned metallics including hariwaki, kikusui, yamatonishiki (metallic sanke), and metallic bekko. Due to the added refinement of the reticulated scales, the Kujaku has a definite advantage over the other members of this class, and is most often selected as “best in class” for hikarimoyo.

Beni Kujaku

Beni Kujaku

Occasionally a Kujaku would be seen with a deep rich red pattern, but it was a rarity as the hariwaki lineage most often results in yellow to orange shades. Recognizing a demand for the red (beni) Kujaku, breeders embarked on the goal of developing a Kujaku with consistently red coloration. A breeder in Niigata, Japan, by the name of Koneko, became the first to achieve this. He reputedly crossed a traditional Kujaku with either a metallic Kohaku or a red Kikusui, and the result has been a new line of beni Kujaku which have become the standard of the breed.

When selecting a young Kujaku for your collection, look for a koi with excellent metallic sheen. Also, check for even, sharp reticulation on all scales. On a tosai (one-year-old koi) this reticulation may not be “up”, so if you are not sure of the breeder it may be best to purchase Kujaku at two years old, when the reticulation is more likely to be developed. The head should be clean and white with no smudging or black markings, and the fins should be a lustrous silvery color. As always, look for a healthy koi that appears to be curious and actively swimming with its tank mates. The pattern on a Kujaku should resemble that of a Kohaku. In other words, pleasing to the eye and balanced from head to tail and side to side. A simple two or three-step pattern seems to work very well with the reticulation. A busy pattern can look too chaotic when coupled with the reticulation.
It can be a challenge finding the “right” Kujaku for your tastes, but when you finally find that elusive red Kujaku, you should consider adding it to your collection.

© Bryan Bateman 2014

THE INS AND OUTS OF KOI POND BUILDING by Mike White, White Water Filters PART 1: Planning

PART 1: Planning

Are you thinking about building or having a koi pond built? In this series of articles I will discuss how to build a koi pond. Why is it important for you to read this article prior to “digging in”? Because quite frankly there are many people in the pond industry that are telling people things that are not true, just to sell their products. Or, they installed a system themselves and feel it is the best.

Why should you take the time to read what I have to say? I have been involved with the koi hobby for over 25 years. I see more than 100 different ponds every year. I sell, install and maintain many different types of pond and koi products. I have worked with both old technology and cutting edge technology. I have written articles for various pond related publications and have conducted seminars. And I will be the first to tell you that there is no such thing as a “perfect” system.

What make a koi pond different from any other pond? The first thing is that this is a pond designed to house large fish, a type of carp, koi. In a large area they can easily be raised to a size in excess of two feet long and may grow to 3 feet long. That is a big fish. A fish this size needs room to swim and grow. But an even larger concern is that this fish uses very little of what it eats. More than 90% of the fish’s intake is expelled as waste.

A koi pond seldom has many plants in it as larger koi will eat almost any plants that grow on or below the water’s surface.

Koi are often costly and because of their bright colors, koi are susceptible to predators. In this area the primary predator of koi is heron, but raccoons can also present a problem. In addition, some times the design of the pond can cause damage to these “living jewels”.

Before you build your pond there are a lot of decisions that need to be made. Your first decision is what are you going to keep in your pond. Since you are building a koi pond, that decision has been made.

Next, you should determine the size and location of the pond. Let me give you a few pointers on this topic. First, water will naturally draw people to that area of your yard. By this I mean that if you don’t build it near your outdoor living area you will end up with a new outdoor living area – near the pond. Secondly, it should be close to and easily observed from your house. I guarantee that even while in your house you will look out to see the pond all the time. The closer, the better!

As for size, most people will tell you that you can’t make it too large. That isn’t necessarily true. If it is too large, it will be hard to see the fish or catch them when necessary. Your pond should be built so that all areas of the pond are within reach of a koi net extended to no more than fourteen feet. What this means is that you should be able to walk down one side of the pond or across a bridge and be able to reach every area of the pond. If you can’t do this, it means that you will have to use a seine net or have a helper every time you want to catch a fish in the pond. Yes, I know there are experienced pond keepers who break this design rule and can catch the fish. But it takes a great deal of experience to be able to do this. Or you are going to say, I don’t plan on having to catch any fish but that view is unrealistic.

If at all possible, the pond should not be in direct sunlight all day. Ideally, no more than four to six hours of direct sunlight should be on your pond during the summer. In the best arrangement, shade should be provided by a building or structure, but this isn’t always possible. If trees provide your shade, there will be a problem of debris from the trees getting into the pond. If it is not possible to avoid this situation, don’t worry about it. I am talking about ideal circumstances. I am always going to present the ideal ponds, but in building a pond there are always trade-offs from the ideal.

In future issues I will discuss pond design, skimmers, bottom drains, pumps, filtration, ultra-violet lights, ozone, aeration, plumbing and other pond equipment. Not everyone can build their ideal pond at the outset so I will also talk about pond building in stages based upon budgets.

©2004 all rights reserved to Mike White

THE INS AND OUTS OF KOI POND BUILDING by Mike White, White Water Filters PART 2: Design

PART 2: Design

In this series of articles I will not endorse any brands or manufacturers. I may talk about different manufacturers but if I don’t mention a particular company it in no way implies that I feel a product is inferior or doesn’t measure up. I will tell you what I would look for in a product. If a product meets the criteria I use, does not imply that it is the best, only that it meets the specifications I am looking for. All opinions expressed are my own.

This part will discuss pond design. The first item is the shape of the pond. In the first article I talked about the sized of the pond. The ideal shape is a perfect oval, however most people don’t construct a pond in a perfect oval. Why is the perfect oval ideal? This shape provides the best possible water circulation in the pond. The cross section of the pond should reveal a bowl shape. The bowl shape provides a good way to get the debris to the bottom drain. Once again, I am speaking of the “ideal” shape.

Now that we know what the ideal shape is and why it is considered such, you can work on determining the compromises you are willing to make to result in the aesthetic design you want.

There is more to pond design than size and shape. There are various pieces of equipment on the pond, circulation of the water and filtration equipment to be used.

Circulation of the pond is how the water moves through the pond. Our koi ponds are not stagnant pools but closed systems of circulating water. Water circulation can come from many sources, such as waterfalls, streams, jets, and return pipes. All the moving water is a result of water being moved by pumps.

Ideally the pumps should move the entire volume of water once per hour. In addition, “ideal” circulation would mean every drop of water in the pond is in constant motion. Most ponds accomplish water circulation through the use of waterfalls. If we are talking of the ideal way of moving water, this is actually the least preferable. Waterfalls can drastically affect the temperature of the water and bring large amounts of debris in. Waterfalls also attract birds, bringing additional undesirable elements into the pond in terms of parasites, waste, etc.

Water circulation can also be achieved through the use of air injected into the water. Air is the most efficient way to move water.

I have yet to see a pond with ideal circulation. Most ponds have very poor circulation and this can be a major cause of problems. The movement of water is very difficult to see at best or impossible. The use of a dye or colorant can help illustrate how the surface of the pond circulates. The reason I say “surface” is because when the water has colorant in it, it makes it hard to see through the surface to the water lower down.

Next I would like to address devices that allow water to be moved outside the pond. The first of these is a skimmer. The purpose of a skimmer is to remove surface debris. The first skimmers used on ponds were swimming pool skimmers. About 25 years ago a company called Aquascape Designs incorporated the design of swimming pool skimmers into a larger container. With the use of a net instead of a basket, more debris was allowed to collect before the skimmer became full. Approximately 16 years ago Pond Supplies of America radically changed this design. Instead of using a swimming pool weir, they used a device they call a bellows. A weir is supposed to take the water just off the surface of the pond. A swimming pool weir is designed to allow water to enter the skimmer not only from the surface but also to a depth of about 5 inches. This decreases the efficiency of the weir. Pond Supplies of America designed their bellows so that only the surface water is taken into the skimmer, improving the efficiency of the skimmer. Since that time, there has been an explosion of skimmers on the market; some good and some not so good.

When looking for a skimmer one should inspect how the skimmer is built. A skimmer is typically buried in the ground. The pressure of the dirt around it tends to deform the skimmer unless it is built strong enough to withstand this pressure. When the skimmer is deformed (misshapen), it cannot operate properly. Most modern skimmers have a net or basket to catch large debris and then a polyester pad to catch finer debris. These units provide mechanical, not biological, filtration. This means they mechanically remove debris from the water. Don’t worry about using chlorinated water to clean the net, basket or pad. Expect to have clean these items. The better they are working, the more often they will need to be cleaned. Recently brushes have been added to skimmer design to catch more debris. The vast majority of debris in a pond comes from outside sources such as leaves, seeds and pollution in the air. Of course I am talking about outdoor ponds as most ponds are located outdoors.

In the next article I will discuss other devices that move water outside the pond, pumps, and returning water to the pond.

©2004 all rights reserved to Mike White

THE INS AND OUTS OF KOI POND BUILDING by Mike White, White Water Filters PART 3: Circulation

PART 3: Circulation

In the last installment we discussed circulation a great deal. The reason circulation is an important topic is that everything that lives in the pond depends upon circulation or lack of circulation. Water circulation takes place both in the pond and outside the pond. To circulate water outside the pond it requires a force on the water to get it to move. This force commonly is either gravity, a pump or air.

Gravity and pumps are commonly used to circulate water outside a pond and are usually used in conjunction with each other. A pump is used to either lift water above the level of the pond so that gravity can be used to move it back to the pond. Or a pump sucks water out of a container attached to the pond, such as a skimmer or vortex settling chamber, and gravity returns water to the container to replace the water that has been removed.

Now I would like to discuss pumps. Pumps are usually classified as one of two types; submersible and external. Submersible pumps are designed to run submersed in water. If they run out of water, they will over heat. They are usually located in the skimmer or in the pond. Most submersible pumps are filled with oil to transfer the heat from the motor to the water. They usually have a life span of less than four years if used in a pond. It is usually not recommended to rebuild submersible pumps. Submersible pumps are easier to install and less costly. For these reasons, submersible pumps are used in ponds.

External pumps are located outside the pond and are cooled by the air. If an external pump is submersed in water it will short out the motor. External pumps use air for cooling. They usually have a life span of 7 to 10 years and normally can be rebuilt with no problem. External pumps are generally more energy efficient.

Regardless of the pump used, it should be matched to the application. Another concern is the amount of energy consumed as the typical pond in this area runs about 8 months a year, 24 hours a day and seven days per week. What sounds like a good deal when you buy the pump could end up not being the case.

How do you determine what is the best pump for your application? This is not a simple matter. First you must determine exactly what the application is and how much water will be required. Then the static and dynamic head pressure the system will have must be calculated. This can then be matched to the pump curve and that will determine which pump will work in your application.

Another means of circulating water is the use of gravity. Gravity is a constant force that pulls toward the center of the earth. Since water is a fluid, gravity is always going to try and pull the water to the lowest point it can flow to until it is contained. Once water is higher than the pond, as long as there is a path for the water to flow back to the pond, it will flow there. This is how a skimmer works or how a waterfall works. If you are using gravity to move water through a pipe, the sizing of the pipe becomes critical. In this case you should consult with an expert to make sure the diameter of the pipe is the correct size. Gravity is the cheapest way to move water but may not be the most efficient.

Using air to move water is a very efficient method if moving the water to a very limited height. The devices used are called air lift tubes. An air stone is placed in a body of water and then a pipe is placed over the air stone. The air going up the pipe moves water with the air out of the pipe. This can move a lot of water.

Why would water be circulated outside the pond? Some possible reasons could be to run a waterfall, stream, or filter.

I have discussed water circulation and equipment extensively for one reason; the better the circulation, the better the pond is going to operate. The poorer the circulation, the more problems there will be with the pond.

In the next installment I will discuss filtration.

©2004 all rights reserved to Mike White

THE INS AND OUTS OF KOI POND BUILDING by Mike White, White Water Filters Part 4: Mechanical and Chemical Filtration

Part 4: Mechanical and Chemical Filtration

In this article we are going to discuss filtration. Filtration is broken down into 3 different types; mechanical, chemical and biological. I will be discussing each type in detail. This article will cover mechanical and chemical filtration with biological filtration to be covered in the next article.

To begin, we will cover mechanical filtration. Stated simply, mechanical filtration removes debris or compounds from the pond through a mechanical device. The device could be as simple as a net or as complicated as a foam fractionator. Every mechanical filter has a specific purpose. When looking at mechanical filtration it is important to first identify what you are trying to accomplish and then choose the correct product for the solution.

Most commonly on a pond we see a skimmer; which is a mechanical filter used to remove floating debris from the surface of the pond. Within the skimmer there are usually two different devices. First a weir designed to take water from the surface. Next a net or basket is used to collect debris. When looking at mechanical filters, we need to analyze how well it will do what it is intended to do. Using our skimmer example, let’s break down how it is supposed to work and determine what to look for in a skimmer.

The first thing a skimmer is supposed to do is remove debris from the surface using a weir type device. Water is intended to enter the skimmer by going over the top of the weir that floats so that only a thin layer of water goes over the top. Therefore, any water that enters the skimmer opening by not going over the top is a waste. In this way we can get a good idea of how well it will work by looking at its construction.

Most skimmers use a door that is hinged at the bottom. Yes, water will go over the top as long as the amount of water being pulled in is more than the amount of water going under the door and along the sides of the door. If the skimmer has an 8 inch weir with a ¼ inch gap around the door, the area of the gap would be approximately 5 square inches. That is almost the same amount of area as a 2 inch pipe. This is with the door shut, but as the door opens, the gaps on the sides get larger and less water is drawn from the surface. With the door shut as much as 1000 gph can go around the door before it starts to take water from the surface of the pond.

The second part of the skimmer is the net or basket that catches debris. The first thing to look at is whether the net or basket is going to catch all the debris entering the skimmer or can some of the debris get past without being caught. Also make sure the holes in the net or basket are the correct size to catch the debris you are trying to remove from the pond.

Every pond should have at least one mechanical filter and usually more than one. Not every mechanical filter is easily examined to determine if they will indeed perform the work they are intended to perform. A good example is a foam fractionator or protein skimmer. Their purpose is to remove dissolved organic materials from the water. One problem is that you can’t see these materials so how do you determine if the device is going to work? Even though you can’t see them, you can see the effect they have on the pond water. The dissolved organic materials will cause bubbles on the surface of the pond to take longer before they break. With this knowledge we can determine how well the foam fractionator is working.

Next let’s cover chemical filtration. Chemical filtration is accomplished by adding a chemical to the water to remove some substance from the water or tie it up so that it is no longer harmful. Chemical filtration has a limited use in that once the chemical is used up it no longer has an effect on the water. Chemicals used for this type of filtration can range from dechlor to ozone.

As with any filter you should first determine what you are trying to remove from the water. You then select a chemical to address that problem. In some cases it is important to know the volume of water you are trying to treat or the amount of the substance you are trying to remove. Sometimes if too much of a specific chemical is added it might poison the pond life. It is also important to know that in some cases once a chemical is added to the pond water, it stays in the water until it is removed or used up. Many chemicals do not dissipate in the water and they don’t evaporate. Because of this, when you add different chemicals in the future you may have a chemical reaction between the two that could result in undesirable or harmful conditions. Removing one chemical from the pond is not easy. It can be removed by water changes but to remove 99% of the chemical by water changes would take a change of 8.9 times the volume of the pond. For example, if you changed 5% of the pond volume once a week it would take 178 weeks to get 99% out. That is approximately 3 and a half years! The same would hold true for medications.

A word of advice; be careful of anything that you put in your pond because it might be there for a long time. Of course there are some chemicals that disappear fairly quickly. Ozone is one of these. It has a half life of 4 minutes in ideal conditions and much less in any other conditions. What, you ask, is ozone and what does it have to do with a pond?

As ozone is one of the newer ideas being used in the pond world I will explain it as simply as I can. Oxygen normally forms molecules as two atoms of oxygen (O2) but ozone is one molecule of oxygen with three atoms of oxygen (O3). Because the third atom of oxygen, ozone is always trying to get rid of that third atom. Because of this it is a very powerful oxidizer. In fact it is the second most powerful oxidizer known to man. How does that apply to a pond? It means that it can oxidize any organics in the pond. In fact it can be so efficient at oxidizing nitrite to nitrate that the bacteria that would normally take care of this can die off due to a lack of nitrite for them to eat. A word of caution, ozone can be a very dangerous compound and should not be used unless you know what you are doing.

As stated earlier, the next article will cover biological filtration.

©2004 all rights reserved to Mike White

THE INS AND OUTS OF KOI POND BUILDING by Mike White, White Water Filters Part 5: Biological Filtration

Part 5: Biological Filtration

In the last article we discussed chemical and mechanical filtration. In this article I will cover biological filtration.

What is the purpose of a biological filter? It is the removal of toxic compounds by means of living organisms. The typical toxic compound would be ammonia and a living organism would be a bacterium. Doesn’t bacteria grow everywhere in a pond? Then why do we need a filter? The answer is that the pond does not necessarily need a biological filter in addition to the bacteria that is in the pond. In looking at nature, we realize that natural ponds and lakes do not have biological filtration in addition to the bacteria in the natural body of water.

So why are there so many biological filters on the market? Because there is one major difference between a natural body of water and most koi ponds. A natural body of water has very few fish in comparison to most koi ponds. For this reason, a koi pond needs to have a biological filter added to it.

What is a biological filter? It is a device that provides additional area to grow bacteria on. Bacteria will grow on almost any surface. Bacteria are microscopic organisms and therefore a great number of them can live in a very small area.

To understand how the biological process works in a pond with a biological filter we need to understand the nitrification cycle. Ammonia is converted to nitrite by one type of bacteria and then another type of bacteria converts the nitrite to nitrate. Both ammonia and nitrite in small amounts can be harmful to fish. In large quantities, nitrate can be harmful, but usually is somewhat less harmful in small quantities. To complete the process there are two different bacteria involved. The bacteria that converts ammonia to nitrite is very hardy and can easily live in any kind of filter that will support life. The bacteria that converts nitrite to nitrate is easily killed off and takes a quiet environment to survive. Because of this, this bacteria may not be able to live in a lot of filters.

Next we need to take a short course in chemistry. Chemically ammonia is NH4. This is then converted to nitrite which is NO2. This is converted to nitrate which is NO3. By looking at this process we see that hydrogen atoms are released and oxygen atoms are used to convert ammonia to other compounds. Why do we need to know about this chemical process? By understanding how a biological filter works, we can determine how well a filter will work.

Let’s talk about how a biological filter works. The bacteria that is used in this process attaches itself to a solid surface. The bacteria is not free swimming. The food this bacteria lives on must be brought to it in order for it to survive. In an aquatic environment this means that the water must move the ammonia to the bacteria. In our chemistry lessen we learned that for the conversion of ammonia to nitrite and nitrate, oxygen is needed. The oxygen has to come from the water or the air depending upon the filter. This results in a great deal of the oxygen in the pond being used up by the biological process.

Knowing what happens in a biological filter, it is now easy to understand how a biological filter works. Stating it simply, what is needed to make a good biological filter is a media that has a great deal of surface area for the bacteria to grow on and water circulation to the entire surface area of the media. Of course if this was all that was required it would be easy to make the perfect filter. Unfortunately it is not quite that simple. The real problem stems from a topic I discussed in an earlier article. Water always follows the path of least resistance. Because a lot of surface area is needed to grow bacteria, quite a few filters try to send the water through the media to get more surface area. The problem is that when the media starts to grow the bacteria needed, it tends to clog up and the water goes around the media. Even if the surface of the media looks smooth, if we were to look at it under a microscope we would see that it is actually rough. This provides the bacteria a lot more surface area to grow on. These tend to clog up very quickly, thus losing a large share of the surface area. These are just two reasons that biological filters start to break down.

Not too long ago the Japanese believed that a biological filter had to be 1/3 the size of the pond. The English thought that it had to be 15% of the pond volume. In reality there are not too many ponds in this country where the biological filter is 1/3 the volume of the pond. Explaining this further, if the pond volume is 3000 gallons, then the filter would be 1000 gallons. That sounds awfully large. So why did the Japanese want a filter that large? They determined number by trial and error and found this formula worked the best. At the time they were using stone as their filter media. Stone has a very small surface area for the volume that it takes up. It also tends to clog up easily. For both these reasons a large filter was necessary and it worked wonderfully. At the time it was believed that the water going through a filter had to stay in the filter for 20 minutes. Based upon this, the entire volume of the pond would need to go through the filter every hour.

Why did a filter this simple work this well? First it is now known the water going through the filter doesn’t have to stay in contact with the bacteria. In fact, bacteria grab the toxic compounds as soon as they come in contact with each other. By keeping the turnover rate through the filter ton once per hour it kept the ammonia and nitrite levels extremely low in the pond. Because the flow going through the filter was moving at a slow speed, it provided an environment conducive to the bacteria’s conversion of nitrites to nitrates. A filter with faster moving water tends to kill the bacteria.

Finally this filter was so oversized that when parts of it clogged up there was still plenty of filter left to handle the load. This allows bacteria and enzymes the necessary time to eat up the clog, thus enabling the formerly clogged portion of the filter to begin functioning again. Thus this filter becomes self cleaning.

Now before you all start drawing up plans to make a filter like those of the Japanese, there are drawbacks. This type of filter has the potential to become a breeding ground for all types of toxic compounds and nasty critters.

Now that we have some basic knowledge of biological filtration, in the next issue we will take a look at various types of filters on the market. We will review their good and bad points.

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