Laguna Koi Ponds

(949) 494-5107

Library Health Care

Laguna Koi Ponds
20452 Laguna Canyon Rd.
Laguna Beach, CA. 92651
Hours of Operation:
Mon-Fri 9-5 Sat 9-5 Sun 10-5
949-494-5107
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Health Care

By Ben Plonski
Laguna Koi Ponds

Disease Prevention. I would like to discuss the importance of disease prevention. Our koi are very strong fish and do have some natural immunities to disease organisms, if we take care to provide them with a healthy pond. Just like people, koi's natural immunities break down when stress factors become overwhelming. Our goal as koi keepers is to understand and manage these stress factors. Careful pond management will minimize the outbreak of disease. Let's discuss some of these stress factors.

Stress Factors. Koi health depends directly on good water quality. We must provide a clean and healthy pond environment. A dirty pond is a breeding ground for disease organisms. The koi's own waste and excess food are the main source of pollution in a pond other than leaves and debris blown in from the wind. A good filter system will remove the waste products which accumulate and make our koi sick. These waste products are ammonia, nitrite, carbon dioxide, solid waste and sludge. Some of these can be tested for with simple and inexpensive test kits. The filter system removes these waste products by the action of good bacteria which grow in the filter. This is called a biofilter. The bacteria in the biofilter consume a lot of oxygen. A dirty pond consumes a lot of oxygen. The koi also need optimal levels of oxygen to maintain disease resistance. As you can see, oxygen is a very important factor and must be continuously provided 24 hours a day. A waterfall, aeration jets or an air pump are all good sources of oxygen. A dirty pond with low oxygen levels may have a low pH, which is a measurement of acidity in the pond. pH measurements become more acid over the course of time. Koi need a stable and slightly higher or alkaline pH. Monthly partial water changes along with good filtration and aeration will help keep the pH stable.

Another big stress factor is a change in temperature. Koi have a tolerance for a wide range of temperatures. However, temperature changes must occur slowly. Koi's metabolism takes time to adjust to changes in temperature. The koi's immune system is weakened by large temperature changes. Do not expose koi to changes of more than 5°F up or down within a 24 hour period. A koi's immune system is the strongest above 65°F. Large, deep ponds are more stable in temperature.

Excessive handling can really stress your koi. Be careful when catching koi; move slowly and never lift them from the water in a net. Rather, the koi should be guided with the net into a tub or bowl for moving or inspection. Nets can scratch the protective slime coating off the koi. This can open them up to infection.

One of the biggest stresses on the koi is overcrowding. Too many fish will produce a lot of waste and consume large quantities of oxygen. A lot of maintenance is required on overcrowded ponds as your margin for error is greatly reduced. Overcrowded ponds are more susceptible to disease because it is easier for parasites and bacteria to find a weak koi.

All koi have parasites and pathogenic bacteria on their bodies. Too much stress will weaken the koi and the pathogens can proliferate.

Observations of Koi Behavior. Before we can recognize sick koi we must understand what normal koi behavior is. When we maintain a healthy pond we can observe normal healthy koi behavior. Healthy koi will swim freely around the pond together; actively searching for food when water temperature is above 50°F. In general the koi show interest in each other and eagerly accept food. Their fins will be held out straight. The gill movements will be relaxed. The eyes will be clear and the colors will be bright. As you become familiar with normal behavior you will recognize any deviations which will be the clue that something is just not right. Sick koi may hang off by themselves away from the crowd. They may list at the surface gasping for air or remain motionless at the bottom of the pond. They may not feed as eagerly as usual. Sick koi may produce a lot of mucous and the skin or eyes may look cloudy white. Koi produce mucous to protect themselves from parasites or bad water. Often the colors will fade or the skin may appear pinkish. Some diseases will cause the koi to rub themselves on the bottom of the pond or they may leap from the water in an effort to rid themselves of the problem. Scratching or jumping is not done in fun. Parasites and /or poor water quality are usually the cause. Spend time watching your koi every day so you will notice problems early. Some koi diseases can spread very rapidly and early diagnosis helps ensure a successful recovery.

Process of Investigation. When we observe abnormal koi behavior we must begin an investigation into the possible cause. Abnormal behavior may be the result of a stress factor alone. The behavior may also be the result of a specific disease organism. The koi's symptoms are a generic reaction. The symptoms are not a conclusive indication of disease. We must first understand and alleviate the cause of the stress before we can successfully treat any disease organisms. Let's consider the process of investigation.

We can begin our investigation by testing the pond water and environment first.

  • Test for oxygen. Results should be above 5 ppm, preferably 8ppm or higher.
  • Test for ammonia and nitrite. These tests should read zero.
  • Test the pH. A range between 7.0 and 8.0 is acceptable. However, daily fluctuations of more than 0.2 are stressful. A stable pH is important. These tests will give you clues about the water quality. Poor water quality must be corrected. Careful consideration should be given to your filter system and your management techniques.
  • Check the pond for obvious dirt and organic matter. Dirty ponds consume too much oxygen and are a breeding ground for pathogens.
  • Check for temperature changes. Have the koi recently been exposed to temperature changes of more than 5°F? Thermally stressed koi take time to recover their full strength and may fall prey to pathogens during recovery.
  • Check for chlorine. Chlorine and chloramine are added by the city water companies to disinfect tap water. Untreated tap water will kill your koi very quickly if not neutralized. Be sure to use a proper tap water conditioner on all new tap water going into the pond.
  • Do not allow any runoff from your garden to enter the pond. Insecticides and fertilizers are extremely toxic and should be used cautiously around the pond.
  • Have new koi been recently added? New koi will be weak and may need time to adjust. New koi can initiate disease outbreaks. New koi can have parasites which may spread to the others. Adding new koi may require preventive treatments or quarantine.

Fortunately, a stable population of koi in a healthy pond can become resistant to their own set of pathogens. A stable pond environment should be every koi keepers goal. Every effort should be made to correct or prevent environmental stress factors as soon as possible.

Once we determine that the pond environment is not the cause of abnormal behavior, we can consider the possibility of parasites being the problem. Although a microscope may be required for an accurate diagnosis of some parasites, access to a microscope may not be practical. Fortunately, we can divide parasites into a few groups which can be treated without actually knowing the specific parasite. These groups can be divided into parasites which are visible to the naked eye and parasites which are microscopic. Eliminating possibilities can lead us to a reasonable conclusion and course of action.

Now is the time to gently scoop the koi into a shallow tub for a visual inspection. Use a large koi net designed to collect the koi without actually lifting him from the water. Scoop him into a special round blue tub with enough water to just expose his top fin; this will reduce jumping. Look closely at the skin and fins of the koi. We will first look for obvious parasites which are visible to the naked eye. Secondly, we will consider the possibility of microscopic parasites. These two categories of parasites will require two separate treatment programs.

Visible Parasites. Large parasites like fish lice and anchor worm can be seen when the koi is up close. Fish lice look like a round greenish clear bug on the skin and fins, about an 1/8 inch to 3/8 inch in size. Anchor worm appear as a greenish or white thread which sticks out from under the koi's scale also 1/8 to 3/8 inch in size. Anchor worm attaches itself with hooks under the scale. Fish lice can cover the whole body in severe cases Early infestations of both these parasites cause a lot of irritation to the koi who will jump and scratch on the pond walls frequently. and the koi become increasingly weaker and tend to huddle together on the bottom. Both of these parasites bore into the skin and cause inflammation around the attachment site. Sometimes a red sore is all you will originally see from a distance. These red sores can lead to a bacterial infection if left untreated. Fortunately, fish lice and anchor worm are easily treated with Trichlorfon or Dimilin.

Treatment of Visible Parasites. Use a Trichlorfon based medication (Trichloracide®) in the pond according to directions on the product. This medication can be found in any good koi retail center. The parasites have a life cycle which is temperature dependent. Parasite infestations above 60°F usually require one application treated every 5 to 7 days for a total of 4 treatments. Parasite infestations below 60°F may require treatment every 10 days for a total of 4 treatments. When water temperature is below 50°F these visible parasites do not reproduce very quickly and are not usually a problem. Be aware that Trichlorfon is deactivated more quickly in warm alkaline pond water. Dosage rates may need to be increased if your pond pH is over 8.0 and temperature is above 78°F. Use extreme caution. The Trichlorfon treatment will kill the adult stage of fish lice. The koi will feel much better after the first treatment. The eggs of fish lice are protected from medication. The follow up treatments will kill the newly hatched larval stages. Adult anchor worm on the other hand is not killed by the Trichlorfon. The treatments will kill the larval stages only. 4 to 5 treatments may be required to eliminate the life cycle and adult stage. Adult anchor worm can be removed carefully with a tweezers by pulling the parasite straight back towards the tail of the koi. This technique is tricky. Give the koi a salt bath with 1 pound of rock salt per 5 gals. for 5 minutes, only. The exact salt bath technique is given later. This will calm the koi down and loosen the anchor worms grasp. The hooks of the anchor worm must be pulled out otherwise the parasite will grow back. Apply a dab of mercurochrome to the attachment site to hinder bacterial infection.

Treat obvious visible parasites first. When sick koi do not show any visible parasites, we must consider the possibility of microscopic parasites.

Microscopic Parasites. Microscopic parasites cannot be seen on the koi's body during a visual inspection. What can be seen is a milky mucous or excess slime on the body and fins. Check the eyes for a white film. The koi produces mucous to protect himself from parasites. The mucous is the koi's first line of defense against pathogenic organisms. Never lift the koi from the water in a net because this mucous can be removed. Other symptoms of possible parasites is a pinkish color to the skin with many red veins apparent. The koi may be weak or lack appetite. Pectoral fins are often held in clamped to the body. The koi may scratch on the pond walls or try to jump from the water. Again these are generic stress reactions and do not define any specific parasite. Fortunately, the microscopic parasites associated with these symptoms can be treated with a few common medications. The actual species of parasite does not need to be identified. Instead, the hobbyist can go through a systematic treatment program which will control most of the potential parasites.

Treatment of Microscopic Parasites. Add rock salt to the pond at 3 to 4 pounds per 100 gals. as a long term bath of 2 to 3 weeks. This produces a 0.3% to 0.5% level of salt. Be certain to divide this dosage over two days so the pond and koi can adjust. This level of salt has a soothing effect on the koi and can help control some of these parasites. Rock salt helps the koi deal with stress. Koi normally lose internal body salts to the surrounding water by diffusion. The koi must expend energy to regain these lost salts to maintain its health. This is called osmoregulation. When a koi is weak or under stress, osmoregulation is more difficult. Adding salt to the pond will help the koi retain its body salts. Rock salt will help the koi save vital energy. More energy can be directed at fighting disease. Rock salt also increases mucous production on the koi. This helps to slough off some of the parasites and protects the koi. Rock salt at this concentration also has an inhibitory effect on the parasite. Rock salt by itself can cure some species of microscopic parasites; however, some species may not be affected at all. Some species of parasites will require chemical medication. Salt treatments usually take 3 to 5 days to be effective. Chemical medications must be used if koi remain sick or get worse during salt treatment. While rock salt is an excellent aid to disease control, it is not a cure all. Dilute your salt level after 3 weeks by making daily 10% to 15% water changes.

A very reliable salt level test kit is available from your pond retailer around $12 that is very accurate. Get one if you plan to use salt. This test kit recommends that you do not exceed 0.14% salt. This is true for plant ponds or ponds with a lot of algae.

A word of caution. Rock salt at 3 to 4 pounds per 100 gallons will kill algae and aquatic plants in the pond. The resulting decay of plant material will pollute the pond and cause oxygen depletion. Weak koi will not survive this additional stress. Excess algae and aquatic plants must be removed before the addition of rock salt.

Salt treatment is an effective therapy for weak koi; however, algae or aquatic plant growth may prevent its use. Salt treatments are not mandatory. You may opt to use chemical medications instead of salt.

The most well known chemical medication for microscopic parasites is a combination of two chemicals called Formalin and Malachite Green. This combination is known under many trade names (Paracide Green, Rid-Ich) and can be found in any good koi pond retail center. Most microscopic parasites can be controlled with this treatment. Use according to dosage on the bottle and treat once every 4 days when water temperature is above 65°F; and once every 5 to 7 days when temperature is between 55°F to 65°F. Treat a total of 3 times. When water temperature is below 55°F, do not treat. The Formalin component can harm your filter if you dose when the water temperature is cooler than 60°F. Likewise if your filter is too small or is recently established you may stunt the good bacteria with the formalin. Use caution and know your pond volume accurately before dosing. Some hobbyists opt to turn off or by-pass their filter for 4 to 6 hours on the day of treatment. Below 55°F to 50°F, most parasites are not a problem.

The Trichlorfon treatment can be used in conjunction with the Formalin/Malachite Green. This treatment has a broader spectrum of control. However, the salt level in the pond should not exceed the 3 pounds per 100 gallons when used with the formalin. Both treatments tend to cause excessive sloughing of mucous when used together and caution is in order. The koi can actually lose its protective mucous which is the last thing we want.


Most of the common parasites can be controlled with these common treatments. However some parasites are becoming increasingly resistant to standard medications. One such parasite is called skin or body flukes. Flukes are microscopic and when afflicting koi can do a lot of damage. The koi will scratch and jump a lot. A lot of mucous is produced by the koi to protect itself. Flukes can open small sores on the koi which can become infected with bacteria. It is important to rid your koi of flukes as quickly as possible. When standard treatments fail you very likely have flukes. Fortunately, new treatments are being developed to control flukes. One effective medication for flukes is called Fluke-Tabs. Control can be gained quickly with this medication, however proper dosage must be followed. Overdosing, as with most medications will do more harm than good. Usually one treatment per week for 2 or 3 weeks is sufficient. Remember, a dirty pond can degrade the treatment and render it non-effective.

Another parasite which is acquiring immunity to standard treatments is called Trichodina. This microscopic parasite also causes the koi to scratch or jump a lot and the koi will produce a lot of mucous. One of the best treatments for Trichodina is called potassium permanganate. This chemical is available through good koi retail centers. Great care must be exercised when using this chemical. Potassium permanganate is an oxidizing agent which can burn your koi's gills if overdosed. This chemical is very useful but must be used properly. Never walk away from a potassium permanganate treatment.

To treat the entire pond with permanganate, use a low dose of only 7.5 grams of pure crystal permanganate per 1000 gallons. of pond water. This is not quite a LEVEL teaspoon. This produces approximately a 2 ppm dose. Mix this dose into a bucket of pond water and spread evenly around the pond. The water will turn purple. As the permanganate begins to decompose the color will turn to brown. The organics in a pond react with the permanganate and cause it to decompose. The brown color determines the termination point of the treatment. A dirty pond will decompose the permanganate within 5 or 10 minutes.

An effective treatment must remain purple for 1 to 2 hours. A second or third treatment may be required once a day for 2 to 3 days. Every treatment will stay purple for a little longer. The permanganate is oxidizing the organics and the parasites in the pond water. Every treatment thus increases the permanganates effectiveness. Every treatment also increases the chance of burning your koi's gills. For the Trichodina parasite usually only 2 of the dosages are necessary to bring things in order. Fortunately, you can deliberately terminate the treatment by adding a dechlorinator solution as for tap water. If you accidentally overdose or you think the koi are in distress, add a dechlorinating agent for the full dose of the pond volume; the color will turn to brown within a few minutes and the treatment is terminated. You must maintain a high level of oxygen with the permanganate treatment. Another benefit of this low dose permanganate treatment is the oxidizing of water born and skin bacteria on the koi. Permanganate is a good preventive to bacterial diseases. A word of caution: Do not use potassium permanganate treatments with new biofilters as this can stunt your good bacteria in the filter as well. Turn your new filter off for one hour while you treat the pond. Ensure good aeration and circulation within the pond during treatment.


Accurate Pond Gallonage Must Be Known Before Any Treatment. Most medications only have a 15% margin for safety or effectiveness. The most accurate way to determine pond volume is to use a meter at the time of filling. Alternatively, fill a 5 gallon bucket and time its fill, then use that number in gals per minute to figure the fill rate from the garden hose.

Rectangular or square pond volume in gallons =

  • (feet) length x width x average depth x 7.5
  • (inches) length x width x average depth Divided by 231

Circular ponds in gallons =

  • radius =1/2 of diameter
  • area = radius x radius x 3.14
  • volume = (feet) areax average depth x 7.5

Irregular Shapes Divide the pond up into circles, rectangles or squares. Add the divided parts together.


Salt Baths. Salt baths can be a quick way of reducing the number of parasites afflicting a koi. Koi which are heavily parasitized can be given a salt bath to help speed up the pond treatment. Also, new koi can be given a salt bath before being introduced into the pond. This can really make a difference, especially with flukes and trichodina. To give a salt bath follow these steps.

  1. Put 5 gals. of pond water into a large tub or bucket big enough for the koi to be comfortable. Use only enough water so the koi's top fin is just under the surface.
  2. Add rock salt at 1 pound per 5 gals. to the tub and mix to dissolve.
  3. Be sure the bath is well aerated before placing the koi in it.
  4. Gently transfer the koi with a plastic bag and place him into the salt bath.
  5. Bathe the koi for 5 minutes only. Do not leave the koi alone. A weaker koi will tend to roll over on its side within a few minutes, while stronger koi may remain upright for the entire bath. Remove weak koi in 3 minutes; remove stronger koi in 5 minutes.
  6. Transfer the koi back to the pond by plastic bag and he will soon regain his equilibrium.
  7. Salt baths may be given every 2 days but only until the koi shows improvement. Usually only 1 or 2 baths are necessary. Repeated salt baths are unnecessary and will only weaken the koi.

Follow up treatment in the pond may be given by any of the standard treatments already covered. The salt bath will not kill any of the parasites which are free swimming in the pond or trapped in the filter. The salt bath cannot kill every parasite on the koi but it can greatly reduce the numbers.

Natural Balances. Koi have lived with parasites and other pathogens since the time of their origin. Koi in a well maintained pond can live in a natural coexistence with parasites. Remember, the goal is not to annihilate your koi with every known medicine. A panic approach to disease control usually kills the parasites and the koi. When koi scratch or act odd do not immediately dump chemicals in their home. Use the process of investigation and elimination we discussed and treat for specific problems. Calm down and use your common sense; give the koi some time to recover from mild problems with improved water quality and filtration. Just like a dog who has a few fleas we do not panic and over kill the situation. This sets us up for worse problems down the line. Prevention is the key. Good water quality and fewer fish tend to be a more suitable approach to prevention. Take care of your water and the water will take care of the koi.