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Please take a moment to review the following articles that have been written by our club's Koi Health Assistants, Don Harrawood and Ken Austin.  Other articles are credited to others as indicated.


Are you using zeolite in your pond? If you are, pay attention to this:

Zeolite clay is very effective in removing ammonia from pond water. Zeolite can be purchased at many aquatic products stores; however, they seldom tell you of the dangers of using zeolite.

In the pond, zeolite removes ammonia through ion exchange. It releases sodium chloride (salt) into the water and absorbs toxic ammonia. The danger here is if the pond owner adds salt to treat for parasites without removing the zeolite, the salt then is absorbed by the zeolite causing it to release all the ammonia that it has absorbed. This spike of ammonia can be enough to be very toxic to fish. Don’t forget to remove zeolite from your pond before adding salt. Some pond owners have lost their entire collection of koi by adding salt while using zeolite.

Zeolite can be "re-charged" by removing it from the pond and placing it into a container containing 3.5% to 4.0% salt water (3.5 to 4.0 pounds salt per10 gallons water). After 24 hours, rinse well and return it to the pond where it will again release sodium chloride and absorb toxic ammonia.

Don Harrawood

Koi Health Advisor


Ultraviolet Lamps

Ultraviolet lamps attached to a pond’s water circulation system is the best safeguard against "green water" algae. This safeguard, however, is limited to the effectiveness of the UV light itself. It should be of proper size, installed properly in the pond system, and maintained (bulb changes) to be effective.

How long has your ultraviolet lamp been in service? Please be aware that UV lamps have a rated effectiveness of one year. Even though the lamp is still glowing after a year, it has greatly reduced in effectiveness. After a year’s service, the lamp should be replaced with a new one. Green water is not very prevalent during the colder months, so you can stretch lamp life to two years by turning your lamp off in October and back on in April. If your water is starting to turn green, and you have a working U.V., it is time to replace the old lamp.



Sand filters are great for swimming pools, but not so great for a koi pond. Why is this? As the fish waste in the water is filtered through the top layer of sand inside the filter, it is kinda like glue and it forms a crust on the surface of the sand bed. If the filter is not backwashed very frequently, the crust gets so thick that the sand filter will not backwash well. What happens during the backwash cycle then is that water pressure punches a hole through the crust of the sand bed and the backwash water runs through the hole and is wasted. The sand is not fluffed and washed as it is supposed to be. At this point, in order to make the filter work properly again, the filter must be opened up and the sand cleaned by hand. This is a time consuming and rather tedious job.

Some pond supply companies now have offered a solution to this problem. We are seeing new media on the market that replaces the sand and does a marvelous job. We have seen sinking beads, various kinds of plastic media, and light weight materials to replace the sand. Probably the material most recommended to replace sand is a plastic tubular material called Bio-Tube Aquamedia. This material can be purchased locally from a supplier that handles Aqua Ultra-media. The Bio-Tube media from Aqua is tubular cylindrical plastic media with a "Y" shaped web inside the diameter. The area inside the media is designed to support bacteria, and to protect bacteria colonies from being removed during the tumbling process of backwashing. Its use results in low pressure loss of the system and a very high bio-film surface. This material then becomes a good filtration and biological filter media.

If you have sand in your koi filter, it is recommended that you consider the Bio-Tube media in place of sand. With this media your filter will not clog up, it does an excellent job of filtration, and backwashing the filter is a snap.

                      Media available at

Nash Gardens in El Paso, TX

Don Harrawood

KoiHealth Advisor



      Check pond salt content (starting salinity)

      Add a known amount of salt (make sure it is dissolved and evenly disbursed over time).

    Pounds salt added times 12 divided by ending % salinity minus starting % salinity (in percent) equals gallons pond water including filters.


    A pond was checked and found to have a salinity of 0.10 percent.

    40 pounds of crystal salt was added (dissolved and disbursed thoroughly)

    A new salinity check showed 0.23 percent. Using the formula:

    # salt x 12 ¸ Change in % salinity = gallons

    40# salt x 12 = 480, 480 ¸ (0.23 – 0.10) = 480 ¸ 0.13 = 3692 gallons



    Pond Volume (Gallons) = (pounds salt added X 12) divided by Change in % Salinity

    Change in % Salinity = (Pounds salt added X 12) divided by Pond Volume (gallons)

    Pounds salt to add = Gallons X (desired % change in salinity) divided by 12


    In order to get accurate checks of salinity, it is recommended to use a salinity meter graduated in percent salinity.


What Determines a "Quality" koi?

Some breeders sell koi in three or four different categories; these categories are pond run, selects, premium, and show quality. Other breeders sell koi in only two classifications, these are premium and show quality. Everything that does not meet this breeder’s standards is destroyed, resulting in about a 10 percent yield. The various classifications are determined through a constant culling process, done at regular intervals, where each koi is inspected for quality features and for future possibilities.

Young koi are very difficult for the layman to determine whether it will be a good or bad choice, since the pattern on young koi change with age, maybe several times. As koi grow older, their physical shape, pattern and coloration tend to become more predictable. Koi judges look for definite characteristics when judging the koi for quality. Some of these characteristics are:

      Body Shape and Conformation – A fully developed female will possess a fuller, rounded body than the male. The male will have a slender and tapered body.

      Color – The quality of the color in a koi is important. The colors should be very bright and distinct with well defined separation lines between colors.

      Pattern – The color patterns should be well balanced across the body of the koi.

      Fins – The fins should be well balanced with each other, with no splits or tears. No tears or splits in the tail.

      Scars – Needless to say, scars on the body as a result of ulcers or physical injury can take away from a koi’s value. Other defects, such as crooked mouth, crooked spine, and missing scales are also negatives.

Quality koi generally come from quality breeders who are very selective in their breeding process; however, in general a "quality koi" is one that meets the buyer/owner’s approval. A koi’s true value is determined by the amount that a buyer is willing to pay.

Poisonous Plants 

What most new ponders may not realize is that many plants can be harmful or even fatal for their fish and water life. Here is a partial list     of plants that can be harmful and should not be planted near your pond.

Azalea (leaves)
Baneberry (berries & roots)
Black Locust (bark,sprouts & foliage)
Boxwood (leaves & stems
Buckthorn (fruit & bark)
Buttercup (sap & bulbs)
Calla Lily (leaves)
Caster Bean (beans & leaves)
Cherry Tree (bark, twigs, leaves & pits)
Daffodil (bulbs)
Daphine (berries)
Delphinium (all parts)
Elephant Ear (Leaves and flowers)
Eggplant (All parts except for the fruit)

English Ivy (berries & leaves)
False Henbane (all parts)
Foxglove (leaves & seeds)
Golden Chain (all parts)
Henbane (seeds)
Holly (berries)
Horse Chestnut (nuts & twigs)
Hyacinth (bulbs)
Hydrangea (flower buds)
Jack-In-The-Box (All parts)
Iris-Blue Flag (bulbs)
Lima Bean (uncooked bean)
Jimsonweed ((leaves & seeds)
Juniper (needles, stems & berries)
Larkspur (all parts)
Laurel (all parts)
Lily of the Valley (all parts)
Lobelia (all parts)
Locoweed (all parts)
Mayapple (all parts except the fruit)
Mistletoe (berries)
Mock Orange (fruits)
Monkshood (leaves & roots)
Morning Glory (all parts)
Narcissus ((bulbs)
Nightshade (berries & leaves)
Oak (acorns & foliage)
Oleander (leaves, branches, blossems)
Philodendron (leaves & stem)
Poinsetta (leaves & flowers)
Potato (eyes & new shoots)
Privet (all parts & berries)
Rhododendrom (all parts)
Rhubarb (leaves)
Skunk Cabbage (all parts)
Sweet Peas (seed & fruit)
Virginia Creeper (sap)
Wisteria (all parts)
Yew (needles & seed)



A Few Facts About Koi

      Their maximum life span is about 200 years in exceptional cases. Normal life span is more like 25 to 35 years if cared for properly.

      Their maximum length is about 3 feet depending upon blood line and proper care.

      Koi have no stomach, but have a straight gut. In warm water, koi will digest their food in about 4 hours. For maximum growth, they should be fed what they will eat at 4 hour intervals.

      Koi will eat many things; however it is best to feed them a well balanced koi food, containing at least 30% protein.

      The value of a koi mostly depends upon size, pattern, and color. Realistically, a koi is only worth what someone is willing to pay.

      Koi can withstand a wide range of temperatures and pH values; however a rapid change in either value can cause undue stress and many times will cause death. (Water temperatures from 45º F to 90º F, and pH from 6.5 to 9.0)

      Koi ponds should have areas that are at least 3 feet deep for koi to hibernate in winter, and should have some shade so they will not sunburn (in very shallow water) in summer.

      Koi are "schooling" type fish that desire to be with other koi. To keep your koi content, always have more than one koi in your pond or tank.

      Koi continually excrete ammonia into their surrounding water. If the ammonia level is allowed to become excessive, koi can no longer excrete their waste ammonia and can die from ammonia poisoning. Do not over crowd your pond with fish, and do not over feed. Either condition will add ammonia to the water. A good biological converter will absorb the ammonia and keep your fish healthy.

      Koi get oxygen from the water through absorption in their gills, where oxygen is absorbed directly into their blood stream. Pond water should be kept well oxygenated all year by waterfalls or other forms of aeration.

      Koi Produce thousands of eggs during spawning season. Male fish fertilize the eggs by spraying the eggs with milt. If the eggs are laid in an open area, they are quickly eaten by the other koi. Baby koi will hatch in 3 – 7 days depending upon water temperature. Less than 50 percent will survive.

      Koi get along well with other species of fish, as long as the other fish are not aggressive. Koi will eat their young until the fry show some color on their bodies.

      After transporting koi to another location, float their water bag in the new pond or tank about 30 minutes to equalize water temperature before releasing them. Do not pour water from the bag into the pond or tank. This is a bad practice and can spread disease and/or parasites.

      Most koi have some parasites. Most parasites are microscopic and cannot be seen without the aid of a microscope. A trained specialist can examine your fish and determine if your pond or fish should be treated to eradicate parasites.

      Know the water volume of your pond. Koi can be placed under undue stress and sometimes die because the pond owner over dosed their pond with medication algaecides, or other additives. It is important to know the pond water volume when applying these additives. Proper concentrations will generally not cause undue stress to the fish.

Don Harrawood



Green water and string algae are different forms of algae. Both can cause considerable problems for ponds through out the year. Green water differs from string algae in that it cannot be physically removed from the pond; whereas string algae is stringy or hair like, and can be physically removed.

What Causes Green Water?

Green water is caused by the presence of millions of microscopic algae particles, each consisting of one cell. This algae occurs naturally in almost all bodies of water, and can be a problem in ponds during the spring and summer months. In order to grow, algae requires light and nutrients. An excess of either can result in heavy growth and very green water. The nutrients required for algae to grow are normally nitrate and phosphate. Green water is normally worse during summer months when days are longer, temperatures are warmer, and light is stronger. These factors greatly increase the rate at which green water can occur.

What Causes String Algae?

String algae occur naturally in almost all bodies of water and is encouraged to grow by the presence of phosphate, nitrate and sunlight. Phosphate is a vital component of fish foods and therefore enters the water through uneaten food and fish waste. Nitrate is produced as the end product of the biological filtration and through the natural breakdown of organic matter in the pond. Nutrient concentrations tend to build up in the pond over time particularly in the summer when the fish are more active and being well fed. The increased sunlight plus these increased nutrient levels dramatically accelerate the growth of string algae with some species being capable of doubling its weight each day or two.

Steps for Avoiding Green Water and String Algae Problems

There are a number of pond management techniques that can be called upon to help reduce the growth of algae:

      First, you should feed your fish only high quality fish food. Poor quality diets are not well digested by the fish, resulting in excess waste being produced that contribute greatly to a high nutrient load into the pond. This excess of nutrients will stimulate an increased growth of both types of algae.

      Adding plants to the pond can also help limit the growth of algae, since aquatic plants compete with the algae for the nutrients in the pond water. Water lilies in particular are great for this purpose, since their leaves help cover the ponds surface and shut out much of the sunlight required to stimulate the growth of algae.

      Keep the pond bottom clean and clear of sediment. Decaying of this sediment increases the nutrient load for stimulating the growth of algae.

Controlling Green Water

The most effective way to control green water is the addition of ultraviolet lights (U.V. lights) to the pond water circulation system. These devices work by irradiating the pond water that flows through them with ultraviolet light. This ultraviolet light kills green water algae, allowing it to clump together, so that it can be separated from pond water by a filter. This is an excellent method of keeping a pond free from green water year around. It is important to size the ultraviolet light correctly, as its effectiveness depends on the contact time between the light and the water passing through. In general, an ultraviolet light should support a flow rate that allows the pond total water volume to pass through the light every hour. U.V. bulbs should be replaced approximately once per year in order to keep the unit working effectively. The quartz sleeve containing the bulb should be checked and cleaned periodically. If it gets dirty it will cut down on the amount of ultraviolet light reaching the water.

There are other means of removing green water if you do not have an ultraviolet light. These methods are more temporary. There are many products on the market for adding to pond water to remove green water algae. One I will mention is called AlgaeFix. This product when added, as directed to your pond water, causes the green water algae to clump, so it can be filtered out with a pond filter, or can be skimmed off the water surface with a skimmer net.

The addition of aquatic plants to compete with the algae for nutrients, and to shade the pond to deprive algae of essential light are two natural means of reducing the green water effect. A large water change will remove green water temporarily; however it returns rather rapidly.

Controlling String Algae.

The most effective way of removing string algae is by mechanical means; however this method is distasteful to most people. Again, there are numerous products on the market that will kill string algae. AlgaeFix does a very effective job of killing string algae and eliminating green water when used as directed. After the string algae is killed, you will need to remove the floating dead algae from the pond. Numerous plants in the pond will reduce algae by competing for nourishment from pond water. The addition of shade to the pond will decrease the growth of string algae, since it deprives it of needed sunlight in order to thrive.

Don Harrawood




      Is the water suitable for fish – pH = stable between 7 & 9, Ammonia = 0, Nitrites = 0, Nitrates < 50, Alkalinity (KH) > 80

      Does owner have test kits, use them regularly and keep a record of results?

      Estimate pond volume and count fish. Is pond overstocked? (minimum 20 gals per inch of fish)

      If pond is heavily stocked, is extra filtration/bio-mass in place for high fish load?


      Is there obvious accumulation of muck and dead plant material?

      Is there indication of leakage?

      Is the type and amount of algae normal for age and type of pond?



      Is the filter clean and in proper working order?

      Does the owner have knowledge of cleaning procedures and frequency?

      Is the filter suitable for fish load?

      If there is a UV, is it clean, operable and have a fresh lamp?

      Is owner knowledgeable of the need for water change-outs?

      Does the owner have a supply of dechlorinator and know how to use it?

      Does pond design include full water circulation (bottom drains) and easy solids removal (mechanical filtration)?



      Does the pump run and provide a flow rate consistent with its horsepower?

      Are there any piping restrictions to full pump flow?

      Does the owner have knowledge of need to run pump continuously for aeration and bio-filtration?



      Is aeration adequate for fish load?

      If there is an air pump, does it run and provide a flow rate consistent its horsepower?

      Does owner have knowledge of the need to run waterfalls/fountains continuously for aeration?



      Is the power cabling between the pond and house properly installed?

      Are switch boxes and junction boxes intact and water tight?

      If the pump is submersible, is it connected to a GFCI



      Is there an accumulation of dead plant material?

      Is there a need to re-pot overgrown plants?

      Are the number of plants and potting techniques suitable for a fish pond?

      Are plants located in suitable area of the pond?



      Do fish show any signs of illness? (redness, bloating, isolation, injury, etc.)

      Does owner have knowledge of proper feeding practices/ techniques?

      Is fish food stored in cool dry place that prevents spoilage?

      Does pond have depth and volume for type of fish? (3ft deep and 2000 gallons for koi, can be less for goldfish)



After discussing all the items above, the new pond owner should decide about:

      keeping the pond at all,

      keeping it as is, or

      making some changes in the future.

Here are some recommendations:

1 – If not a member of SKAPA, please consider joining.  (Please see our Membership application located on this website).

Ken Austin, Koi Health Advisor

Conventional Filtration – Basics and requirements

      An efficient filter comprises two important stages – Mechanical and Biological. It is important to understand what parts of your filter are designed to do each job. Koi pond filtration efficiency is affected by the complete pond system design as well as the filter design itself.

      Contemporary koi pond filtration is normally based on pond systems incorporating bottom drains, which act as the primary feed for the modern gravity fed filtration system.

      Ponds incorporating pumped filter systems will never acquire the same efficiency as gravity fed systems because the pump liquifies waste and feeds this ‘oxtail soup’ to the primary stage of the filter and consequently the filter has to work much harder mechanically to clear the water and most filters are too small to provide the necessary level of settlement required for prime water quality.

      Gravity fed systems are installed so that the water level in the filter is the same as the pond (with no flow). With water flowing the level of water in each chamber will be progressively slightly lower

      Regardless of the type of filter system employed, the transfer ports between chambers in the filter must be large enough to cope with the maximum flow rates anticipated to avoid each chamber being progressively starved of water.

Mechanical filtration

      In a conventional gravity filter we have one or more bottom drains feeding the primary filter stage, normally a vortex. The vortex removes a large portion of the solids present by utilizing tangential force to move the dirt to the outside wall of the chamber where friction with the outer wall slows it down and causes it to drop to the bottom of the chamber which is acutely coned shaped. A drain valve at the bottom of the chamber allows the accumulated mulm to be flushed to waste.

      As an alternative a large settlement chamber can be incorporated to allow the dirt to drop out of the water flow to the bottom of the chamber. However, vortexes are very space efficient and to get the same mechanical performance from a settlement chamber it would need to be much larger in terms of volume than a vortex.

      The 2nd chamber of a conventional filter is normally a brush chamber which carries on where the vortex left off. i.e. It is designed to trap the remaining gunge that passed through the vortex. Brushes are actually also very efficient although they are a very old idea. They do however need fairly regular cleaning to ensure they are effective and do not block.

      The first two filter stages described above are normally the minimum requirements for efficient mechanical filtration. If space and budget permits, extra vortexes can be incorporated as can extra brush chambers for enhanced mechanical performance.

      Mechanical filtration is by far the most important element in the pond filter design as without good mechanical filtration, the biological stages of the filter can never work at full efficiency and can eventually become blocked rendering them ineffective. With poor mechanical pre-stages in a filter, the biological stages have to cope with solids, which they are not designed to do. It is a fact that most filters that fail to work correctly fail because the mechanical stages are inadequate.

Biological filtration.

      A biological filter can comprise one or many chambers each containing different media of the users choice in order to achieve the correct level of water purification.

      Biological stages of your filter work by providing an ideal environment for colonisation by bacteria, which are responsible for the nitrogen cycle.

      Firstly Nitrosammonas bacteria breed in the presence of ammonia and live on these compounds as a food source. They oxidises the ammonia and convert it into nitrites. In the presence of nitrites, Nitrobacter bacteria breed and convert the nitrites to harmless nitrates again by oxidisation.

      Both these bacteria are vital for effective pond filtration and they are aerobic bacteria. They can only thrive in an Oxygen rich environment.

      To ensure optimum biological performance we must therefore provide a constant supply of Oxygen to the filter. This is normally achieved by utilising an appropriately sized air pump and air stones within the filter system.

      The airstones can be placed within the transfer ports of the biological stages of the filter, or directly under the chosen media, but should not be place on the bottom of the filter to avoid putting any remaining debris into suspension.

      Media can be for example, Spa, Alphagrog, Japanese matting, Hortag, Sintered glass and Kaldnes.

      Free flow media works best as it does not trap gunge but allows it to pass. Therefore the best conventional media to use is open flow type medias such as Japanese matting. Alphagrog. Hortag and Spa are not free flow medias and can have a tendency to block over time and therefore need to be cleaned more often.

      Remember that matting should be placed in the filter chambers as vertical cartridges and not placed horizontally in order to avoid any possibility of dirt entrapment.

      The new media Kaldnes, is not only efficient at removing ammonia and nitrite, but is the first media to be used in a conventional filter system which actually removes nitrates as well. This give the added advantage that blanket weed growth is much reduced. It is also self cleaning and therefore requires minimal maintenance.

Additional stages.

      Additional filter add-ons can be incorporated to improve water quality further, examples of these devices are:-

      Surface skimmers - used to skim leaves and other floating debris from the pond surface and thereby avoid this material sinking and/or rotting on the pond floor.

      Protein skimming - Protein skimmers remove proteins from the water before the turn into ammonia and therefore aid bio-filtration and improve water clarity. A build up of proteins in the water makes the water look yellow and oily and causes foam to build up on the surface by water returns.

      Trickle towers - allow water to run over media in a chamber so that the media is never submersed and is therefore Oxygen rich. Trickle towers are very efficient bio-filters and also remove Nitrates from water.

      Ultra Violet lamps - designed to disrupt algae cell growth and give clear water

      Fluidised bed filtration - very efficient bio-filtration using coral sand or similar as media which is housed in a tower in such a way as to ensure that the media is constantly in motion and thus Oxygen rich.

      Ozone systems – very efficient at disinfecting the water, providing superb water clarity and providing oxygen rich water.

Sizing and installing the filter.

      The text book rule for filter sizing states that you need to turn over your entire system gallonage through the filter every 2 – 3 hours.

      Water retention time in the filter should be at least 15 minutes ideally.

      So if we use the example of a pond and filter of 5000 gallons we need a pump of 2,500 galls per hour. (This allows for some flow drop in the pipework).

      A conventional filter therefore needs to be 750 gallons to provide the necessary retention time

      Flow rate through the filter can be tested once the system is up and running to ensure the turnover rate is as expected. Back pressure on pumps can be severe and will drastically reduce flow rate if undersized piping is used in long runs with many bends. Increase pipe diameter for longer pipes runs to avoid back pressure.

      Providing the flow rate appears to be correct carry out further tests as the system matures by testing the ammonia level in the pond and in the last chamber of the filter. If the flow rate is correct, the ammonia levels will be approx. the same in both cases.

      If it is higher in the pond than the filter your flow rate is too slow.

      More recent thinking relates the filter size required in direct proportion to the volume of food being consumed and the size of the fish population as both these elements dictate how much ammonia is produced an a daily basis and therefore how large, biologically, the filter needs to be.

      Essentially your filter must be capable of supporting a large enough bacterial population to cope with the total loading of waste being produced in the pond system.

      When installing the filter, keep pipe runs as short as possible especially from bottom drain to vortex. Use 4" pipework. Always incorporate a valve to isolate pond from filter to allow for cleaning and back-flushing of bottom drain pipework.

      Ensure each chamber of filter has a separate drain to allow flushing to waste.

      Design of transfer ports or pipes between chambers should allow isolation of each chamber for cleaning

      Use one vortex for each bottom drain – ideally a separate filter system for each drain if the budget allows.

      Determining Sex of Koi

      Following are a few ways that the sex of koi can be determined:

          Look at the ovipositor (vent). If the koi is 2 to 4 years old and it has reached sexual maturity, a female’s vent will be round to oval shaped and pushed out slightly. A male’s vent will be almost like a "V" or triangular shaped and will be concaved or slightly depressed inward. In very young koi, many female’s vent will appear the same as males.

          In the spring, during mating season (March to July), if you rub their gill plates with your hand you will find that the male’s gill plate will be rough like sandpaper, and the female’s will be smooth.

          During mating season, if you run your thumb and index finger along the leading ray of the pectoral fins, you will feel rough (tubercles) on males, just as you felt on male gill plates. The females will have smooth leading ray edges on the pectoral fins

          This is not true in all cases, but usually the male pectoral fins are larger and more pointed than the female pectoral fins; whereas the female pectoral fins are more rounded. Also male pectoral fins usually have a very straight leading edge; whereas the female pectoral fins are more gently rounded. (This is not true in all cases).

          Usually the female will have a more rounded and robust body than the male, but this is not 100% of the time. A full bodied male will normally have the broad part of his body closer to the pectoral fin area; whereas the female will have the broad part of her body toward the middle of the area between the pectoral and the anal fins.

          In larger koi (not 100%) the male’s head is a slight yellow cast; whereas the female’s head is white in color.

          In young koi, it is a guessing game as to their sex. Sometimes even a six inch male koi will have a vent as described above. In young koi of the same brood, the larger koi are generally males. Also the brightest colored koi are males.


A Word About Water Changes - by E L Johnson DVM

Water changes are simply the removal of some old water, and the replacement of that old water with new water. It sounds so simple but there are problems, nationwide. First, water can be chlorinated. Second, alot of people don't do water changes, at all. Thirdly, failure to do water changes allows the accumulation of background pollution such as phosphates and proteins which inhibit fish health and growth. Finally, water changes need to replenish trace elements and minerals in the water which fish need.

Chlorinated and chloraminated water is usually supplied to hobbyists "at the tap" from municipal water supplies. The water company adds these two chemicals to disinfect the water. Each day, municipal source-water is tested for eggs, spores, ova and cysts of various pathogens. If any are found, it may be that the municipal water authority will double or triple the chlorine or chloramine concentration. Spritzing the water into the pond slowly WILL dissipate a lot of chlorine, but will it dissipate all of it? Dechlorinate. By dechlorinating the water, you can be 100% sure the chlorine is gone and will not harm your fish. When your municipal water supply uses Chloramine, you will be relieved to know that dechlorinator can still bind the harmful Chlorine. The remaining Ammonia should be no match for a cycled (properly functioning, well colonized) filtration system.

In speaking to people from across the country, I found that about forty percent of the hobby is not doing ANY water changes at all. This accounts for recurring illness among the fish, slow growth, and poor color. This is the most common cause of the "seven inch, seven year old" Koi. A koi in good water with plenty of water changes should grow at least 3-4 inches per year. Hobbyists should be encouraged to follow a water change regimen as outlined in the chart below.

"Topping Off" the pond is not a water change. You should know this about water: The solids in water do NOT evaporate, nor do many of the chemicals in the water. This means that the nitrates, phosphates, a good bit of the carbon dioxide, all the salt, minerals, etc NEVER leave the pond and accumulate over time. As the pond water level goes down by evaporation, you may notice that the fish perk up as you add water back. There is a transient increase in water quality after the addition of 'new" water but it's rapidly offset by the dissolution of the existing background pollution. So, "topping off" actually concentrates solids and organic chemicals in the water over time. Real water changes should be endeavored.

Ideal water change regimens

Every week

10 percent water change

OR: Every two weeks

20 percent water change

OR: Every three weeks

30 percent water change

No matter which of the above regimens you pick from above, I HIGHLY recommend that twice to three times per year you should perform a 60-70% water change to really REFRESH the pond. You will notice a real boost to fish health and growth.

Major water change: Simply drain the pond down 60-70% and add dechlorinator. Then refill the pond. Don't do this in the PEAK of the summer as you might chill the fish (I've never hesitated, but that's just me). But SURELY in the early summer and late summer you should find the fish VERY appreciative of this service.

If you are performing the recommended water changes, you should have robust, hungry and healthy fish. Fish may still beome ill, of course, however it is much less common in well managed ponds with LOTS of FRESH Water. Fact is, if you wouldn't swim in the pond, your fish shouldn't be.


Chlorine, Chloramine, and Water Changes 


Chlorine (Cl) measured in parts per million (ppm) is a gas which has been added to tap water to control harmful bacteria.  City provided tap water has been found to have from 0.5 to 3.0 ppm, but higher surges are sometimes observed.  El Paso Water Works add 1.5 ppm chlorine to city tap water. 

Chlorine is a quick killer of koi in small amounts (less than 0.5 ppm).  Even in very small concentrations, chlorine burns the edges of their gills and causes long term ill effects. 

Chlorine is deadly to biological converter bacteria.  Do not use tap water to clean your biological converter media.  It will kill the good bacteria.  Use either pond water of water that has been de-chlorinated. 

An open container of water (such as a pond) will lose approximately 1/4 of its chlorine per day to the air.  Remember, chlorine is a gas and it gradually dissipates to the atmosphere from the water. Using this reasoning, a newly filled pond will lose its chlorine in 4 to 5 days after filling.  If you are making a water change or adding make up water to your pond, you do not have the luxury of waiting 5 days before the fish are exposed to the chlorine. 

Treatment is simple but very essential.  Pond owners should have de-chlorinator on hand at all times for water changes and for emergencies.  De-chlorinator can be purchased at most pet and fish supply stores for about $9.95 per quart.  Another option is to make your own de-chlorinator.  This is easily done by purchasing 500 grams of Sodium Thiosulfate crystals for around $6.  When added to a gallon of water, it provides enough de-chlorinator to treat 38,000 gallons.  One ounce treats 300 gallons. 

When treating ponds after a water change, treat it only for the number of gallons you add, not the entire pond volume.  Adding too much de-chlorinator is not detrimental to the fish.  Adding too little may not get the job done.  Add the de-chlorinator to the pond before adding tap water. 

There are several test kits on the market for testing chlorine levels.  Chemical droplet and pill test kits are available.  The recommended test kit range is 0 to 4 ppm.  If de-chlorinator is used religiously when adding water to ponds, a test is not considered a necessity. 


Chloramine is a compound of chlorine and ammonia that is added to some city tap water to kill harmful bacteria.  Chloramine is not used in El Paso water, so I will not spend much time on this subject.  When chloramines laden tap water is added to a pond, it adds both chlorine and free ammonia to the water.  Adding de-chlorinator will remove the chlorine, but not the ammonia.  A good efficient bio converter will remove the ammonia in short time.  Do not add water with chloramine to a pond that is already showing a concentration of ammonia.  This will raise the ammonia level, possibly to a toxic level for your fish.  If you have chloramine in your tap water and water is added to your pond, the accepted remedies are products called Amquil and Ammo Lock 2.  These products eliminate chlorine and turns toxic ammonia into a non-toxic ammonia, which is not harmful to fish.  Since it does not eliminate the ammonia, testing of the pond water will show positive for ammonia. 

Water Changes: 

Partial water changes can reduce the amount of anything dissolved in the pond water, but not remove it entirely.  Although it is sometimes necessary, draining the pond entirely and refilling should be done as a last resort.  Remember, water changes reduce the “good stuff” in the pond as well as the “bad stuff”.  Pond water is swarming with microscopic bacteria.  The good bacteria are necessary for a healthy pond, so we don’t want to get rid of it all through a total water change. 

It is considered beneficial to make a weekly 10% water change.  Ponds smaller than 5000 gallons should make a 10% water change weekly, and ponds in excess of 5000 gallons should make at least a 5% weekly water change.  Why do we need to make water changes?  Many components build up in the water over time, and this is the only way to reduce them.  Experienced koi keepers know that their koi are healthier and stronger when regular water changes are made.  Any water added due to removal of water in the process of back flushing pond filters is considered a part of the water change. 

When adding make up water for a water change, don’t forget to add de-chlorinator prior to adding tap water to the pond.  When adding water from a hose, spray the water on the surface of the pond.  This will add oxygen to the water while filling.  Don’t fill the pond with the hose in the bottom.  This only stirs up things that have settled to the bottom.  Don’t forget to turn off the water.  You don’t want your pond to run over.   Remember, tap water contains little or no oxygen.  Aeration of the tap water added to the pond is recommended, especially if the water change is 50% or greater. 

Don Harrawood, Koi Health Advisor

Southwest Koi and Pond Association.

                                                       My Koi Are Not Growing? 

If all the factors related to koi growth are in place and your koi are not growing, then there are several possible reasons: 

1.     The genetics is a limiting factor that individual fish cannot and will not get any larger.  Just as with humans, so with koi, each individual koi grows to a different size.  Genetics will determine the maximum size of any individual koi at any stage of its growth up to and including its final size.

2.     The koi you have purchased is old.  It may look young because it is small.  But the fish has surpassed the age in which it has the capability to grow significantly.  For the first 3-4 years of their lives, koi produce growth hormones within their bodies.  This is the period of maximum growth potential.  Without correct nutrition during this initial period, the fish will not grow to its full potential.  Older koi will continue to grow, but at a much slower rate.

3.     Water temperatures and/or oxygen levels are low.  Water temperature is one of the critical factors affecting koi growth.  In general, warmer water up to 80° F increases koi metabolism and promotes faster growth.  In water below 55° koi metabolism slows down dramatically and they eat very little.  At 50° their metabolism stops almost completely and they will not eat.

In general, more oxygen in water is better for growth.  The amount of dissolved oxygen in water is one of the limiting factors in achieving growth in koi, in fact, it is critical for the health and growth of koi.

4.     Physical crowding of fish in the pond.  Over crowding of fish produce two elements that affect fish growth.  a) having to compete for food with other larger and more aggressive fish, and  b) poor water quality as a result of too much contamination from too many fish.

5       Poor Nutrition:  Poor nutrition is a major factor in inhibiting fish growth.  Good nutrition in combination with temperature, oxygen, good water quality, and genetic potential, is possibly the most critical factor in achieving growth.  Under feeding of quality food, is one of the main reasons that maximum growth is not achieved in koi.  This growth / nutrition link must be achieved early in the fish’s life during the period when the fish can grow rapidly.  High protein foods (30% to 38% protein) promote rapid growth in koi.  Koi do not have a stomach, but have a straight gut.  In warm temperatures, they digest their food in about four hours.  To get maximum growth, they should be fed every four hours during the day.  Feed only as much as they will eat in about 5 minutes. 

Don Harrawood, Koi Health Advisor, The Southwest Koi and Pond Association


Koi Hobbyist should know the true value of salt for their koi pond.  Salt is one of the key ingredients for treating a pond.  It is the safest and one of the best medicines to be used in a koi pond.  It is more commonly used in ponds than any other chemical.  Salt has been termed, “The Koi Wonder Drug”.   

Let me explain why: 

1.     Koi maintain an internal concentration of salt in their body fluids higher than the water they live in.  Osmosis causes water to transfer from the lower salinity of the pond water into the body tissue of the fish.  This additional water build up in the fish’s body tissues must be eliminated through their kidneys.  Adding salt to the pond water lowers the osmosis pressure.  This reduces the effort the fish must expend in eliminating the excess water.  The saved energy is then available for use by the fish’s immune system, to take care of other potential problems.  The presence of salt in pond water also helps counteract any nitrite toxicity.  Due to the above facts, koi ponds should contain about 1 part per thousand (0.1%) salt at all times.  1 part per thousand (0.1%) salt equates to 0.8 pounds of salt per 100 gallons of pond water.  This amount of salt in the pond has little effect on water plants, and is very beneficial to the fish.

2.     A specific concentration of salt in pond water will kill most fish parasites.  It has been proven that 3 parts per thousand (0.3%) salt in pond water for a period of one week will kill most parasites; however parasites such as flukes and anchor worms will not be eliminated by salt.  Elimination of these parasites requires a different treatment.  If you suspect parasites and wish to apply salt as a remedy, you should apply one pound of salt per 100 gallons of pond water in three different applications one day apart for a total of 3 pounds of salt per 100 gallons applied over three days.  After one week, you should make a 50% water change to lower the salt concentration to approximately 0.1 percent.  It is advisable to dump this high salt concentration water somewhere it will not effect grass and other plants.

3.     Salt has additional benefits.  0.2% to 0.3% salt in your pond water will cause your fish to increase the mucus layer on their body.  This will increase the fish’s ability to fend off pathogens in the water that are constantly trying to enter the fish’s body and cause infection.  In addition, if fish have sores or scrapes on their body, the salt will aid in the healing process.

4.     Acceptable salinity in a koi pond is 0 to 5 parts per thousand (0 to 0.5%) (0 to 5 pounds per hundred gallons water).  This high level of salt concentration should not be maintained for extended periods, but used only for therapeutic reasons.  Koi can withstand 1% salt concentration without ill effects.

5.     Caution!!!  Use only pure salt with no additives.  I recommend “Solar Salt” which is pure salt crystals.  Solar Salt comes in a blue plastic bag of 40 or 80 pounds, is mainly used for water softeners, and can be purchased at Lowe’s and at Home Depot for about $4 per bag.

6.     The addition of salt to a pond can be used to determine the amount of water in your pond, including water falls, filters, etc.  It is important to know the gallons of water in your pond before adding any kind of medication or chemicals.  This can prevent an over dose of harmful additives.   

Salinity test kits can be purchased at most pet stores that sell fish.  Another method of testing salinity level is with a salinity test meter.  Don’t under estimate the value of salt.

Don Harrawood,KHA

Southwest Koi and Pond Assoc.

(915) 833-9339


When the water temperature in our pond is beginning to drop, we should be feeding the fish less because their metabolism slows down. We should decrease the amount of food given and feed only once a day as the water temperature starts to dip into the fifties. We should provide food with a low protein content. A wheat germ based food is good at this time of year, since it is easily digested. Cheerios is a good choice for late fall and early spring feeding, since Cheerios are packed with vitamins, and contain little or no protein.  Cheerios are very easy for the fish to digest during this period when fish metabolism is not fully functioning.

When the water temperature drops below 50 degrees we should stop feeding altogether until spring, when the water temperature remains above 50.  Although the air temperature may be much cooler or warmer than the water, it takes time for the water temperature to change.  If you don’t have a thermometer in your pond, it may be time to get one.  Using a thermometer is the only good way to determine water temperature.

We should strive to keep leaves and other organic debris out of the pond especially in the winter. As these materials decompose they produce toxic gases (hydrogen Sulfide) that can cause death or disease to our fish.  Since hydrogen sulfide lingers in the bottom of a pond, it is best treated by removing or filtering bottom water.

With their lower metabolism and slower movements, due to colder water,  our fish are more susceptible to predation by raccoons, birds and other animals.  If your pond is three feet or more deep, you will find that the fish will winterize on the bottom at the deepest and (warmest) water level.  This will help greatly in reducing the predator threat, since most predators will not enter into water that deep.

As the foliage on our plants begins to die back we should remove any dead or dying leaves and place the plants deep enough in the pond to keep the roots from freezing. While it is true that some plants will survive if their roots do freeze, it is best to lower all of your plants below the freezing zone.

Since we live in a mild climate with only occasionally freezing, It is to our advantage to keep our pump and filter running through out the winter. The filter will keep debris out of the water and keep the biological converter functioning.  The bacteria in our biological converter will not be active at low temperatures, but will remain alive as long as we keep the bacteria supplied with ammonia from our fish and with oxygen-laden water. When spring arrives and the water temperature begins to rise, the bacteria will start to function much more quickly and keep the water quality at a high level for the health of our fish.

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Last modified: 01/02/18.