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Medic Centre


Some of the information and research findings on treatments medications available on this page has been reprinted with the kind permission of World Renowned Koi Vetinary Surgeon Erik L Johnson D.V.M. at www.koivet.com for which we are most grateful. Good water quality is, without a doubt, the most important factor in ensuring the health and vitality of your koi. Koi are generally hardy and will survive a wide range of adverse environmental conditions. Koi that are thriving always seem active and able to shrug of minor bumps, bacterial infections and parasitic problems.

They will be keen to feed, producing good growth rates and maintaining excellent coloration. In order to get the most pleasure from keeping koi, firstly learn how to maintain ideal water conditions and then leave the koi to look after themselves.

If there is such a thing as a magic cure-all for koi health problems, then it is the biofilter. Think of yourself not as a koi keeper, but as a biochemist, cultivating a colony of nitrifying bacteria within your filter.

The koi in your pond are merely there to keep your biofilter functioning to the best of its abilities. The most useful tool the Koi keeper has is the biofilter, be sure to know how it works and how to keep it working by feeding the correct amounts and maintaining good water quality both for the Koi and for the nitrifying bacteria within the biofilter.

For the latest addition to our filter range see our Bio home.

However you may from time to time experience problems with your Koi so we attempt her to provide you with a general guide to koi ailments and medications.

There is and probably always will be much controversy over which, or what, is the best medication to use for a particular purpose - whether it be for the water or the koi.

We at Karobar Koi are happy to advise on treatment and medication, Barrie is possibly one of the most health consensus koi importers in the country, the treatments and products that we sell are all tried and tested on our own stock over many years and used in accordance with the manufactures instructions will help solve any health problem that your koi might have. Koi Pond Treatments can be found under Medications

When using our proprietary brand medications for your sick or damaged koi you will need a suitable bowl in which to place the Koi in order to properly examine it.

There are many suitable containers on the market ranging from the traditional 'Baby Bath' and as you would expect there are many various shapes and sizes available from our stock range.


Having selected the correct bowl for the job, put enough water in the bowl so that the Koi can move freely ,add some anaesthetic, just enough to gently put the Koi to sleep whilst you go to work on the infected, or damaged, area.

It is important that you do not put too much anaesthetic in the bowl, better to add a measure of anaesthetic when the Koi has settled down in the bowl and see how the Koi reacts during the next few minutes' if it shows no sign of the affects of the anaesthetic then add just a little bit more.

Eventually the Koi will lay on its side, at this stage the fish may not be completely under the anaesthetic and should be left in the solution until it can be lifted just clear of the water without flapping, if it flaps it should be placed back into the bowl.

When it can be lifted out without flapping, carefully lay you koi on a wet towel ready for treatment.

If you are in any doubt about treating your koi then we advise that you seek professional help and guidance.

Your local veterinary surgeon will be able to supply you with anaesthetic or issue a prescription. There are anaesthetic's suitable for Koi on the market one is based on Benzocane and the other is known as MS222 which has been produced especially for anaesthetizing fish.

We cannot in the space of this web site discuss the range of ailments that your koi may be in contact with nor the specific manner in which to treat them but merely attempt to provide a very general guide, if you have a specific problem, Barrie will always be happy to advise you. top


There are many topical dressings, as such, that can be obtained from ourselves we will also provide you with our best advice on their usage. top



Salt is probably one of the best forms of pond and water treatment available and at a very minimal cost ... and salt added to any pond or tank at the rate of 1/2 ounce to the gallon is extremely beneficial, but please seek advice from your Koi Dealer before increasing the dosage rate for whatever reason.

Salt is not always the easy answer and is really a preventative rather than a cure.

It's no good treating a pond for a certain problem if that problem does not exist, It is vitally important that you identify the problem whether it is a parasite or some other problem ,It must be identified first

There is only one sure way of Identifying a particular type of parasite, and that is by using a good quality microscope. top


There are many parasites that invade our Koi and even before you have identified the particular parasite you will know from the way your Koi are behaving that there is something wrong.

They may be 'Flicking' off the bottom drain top or some other object, indicating that they have an 'itch' or something is bothering them. If there is just a single Koi that seems to be troubled - then the problem may not be so bad as to warrant treating the whole pond, if however you have a few Koi doing this and jumping out of the pond in an attempt to shake off the parasite - then this is a clear sign that something is seriously wrong. top


Having identified the problem or parasite, you now need to treat the koi in the most effective manner to eradicate the problem.

Before going on to diagnosis, treatments and the remedies etc., the following points are important to your Koi, your system, and your own understanding, if the problems are to be kept to a minimum and to ensure that any treatment given will be both effective and safe for your koi. together with the treatments, if required.

Ensure that you know the exact volume of your system including the filters.

The dosage rates that we shall be quoting are accurate and whilst a 15% under dose can be ineffective - a 15% overdose can be dangerous ! Never try to guess the volume of your system if you do not know it DO NOT TREAT IT

The anti-parasite medications specified are NOT FISH TREATMENTS they do nothing medically for your Koi.

They are purely to eradicate the parasite that is irritating your Koi. top

Waterborne Parasites

can be divided into two sections, namely those we can see with our eyes and the ones we can't see without the aid of a microscope.

All parasites live on parts of our Koi, be it just the mucus membrane, the dermal layer of the skin itself or the bloodstream and flesh.

Each adult parasite lays many eggs, many parasites do not require a partner to reproduce. Many of these eggs stay in the mucus membrane, others are swept into the filtration system where they will hatch and the cycle will continue with an even greater infestation.

The actual life of these parasites is not very long - probably on a few weeks depending on the water temperature.

Parasites are usually introduced to our ponds by Frogs. Newly purchased Koi may be carrying a parasite and even the most careful dealer cannot be sure that his Koi do not carry a single parasite.

Parasite infestation can damage the fine mucus membrane in the gills reducing the amount of oxygen available for the Koi, and the secondary risk of bacterial gill decay, usually is followed by death.

Parasites also cause Ulcers, they bore holes to enter the body through the protective mucus membrane, an ideal place for the parasites to colonizes and infect.

We can never eradicate the problem of parasites on a permanent basis.

The medications and the dosage rates quoted are only intended to be used with an adequate filtration system running as normal although it is recommended that in certain circumstances, depending on the medication being used, that the Ultra Violet Sterilizers be switched off and do not run your return water through a sand pressure filter for a period of no less than 24 hours as these will reduce the effectiveness of the treatment. There is no single treatment that will eradicate all of the parasites.

Different parasites require a different treatment and with some of these treatments the dosage rates can vary.

Medication treatments are usually effective within 2 to 6 hours following their application, the unhatched eggs however will not be affected at this stage and although the adult parasites may have been eradicated - these eggs will continue to hatch and therefore the pond should receive a second treatment approximately 10 to 14 days later. top



Parasites visible to the naked eye:


This parasite and its eggs are commonly introduced by Frogs and Toads. It is easy to detect, especially on the fins or light coloured areas of the Koi.

The size of this parasite vary between 1mm to 5mm in the adults. They are greenish brown and they attach themselves to the Koi by the suckers they use to hold onto the body of the Koi - they also inject a poison into the Koi which causes inflammation and possibly bleeding from the wound. top


Although uncommon in purpose built Koi ponds they are usually visible and look like a small flat worm between 5mm and 20mm long. They are brownish red in colour and again these attach themselves to the Koi by their suckers. top

Method of Eradication:

To eradicate both of these parasites quickly, with the water temperature be above 48 degrees, use Masoten which is an organophosphate-based drug produced especially to combat some of the Water-borne parasites - it is made in Japan although supplies are increasingly difficult to obtain. Method 1:- Masoten Powder at the rate of 1 gram per ton (220 gallons) of pond water. Measure out the quantity required and mix in a plastic bucket or similar (not metal) making sure that all the powder is dissolved and when the water is clear and a beautiful pale blue (like aquamarine) pour the solution round the edge of your pond - if you cannot get right round your pond then pour where there is a good flow of water which will disperse the medication quickly into all areas of the pond.

Method 2:- Masoten Liquid at the rate of 5ml per ton (220 galls) of pond water, mix and disperse as above. A second dose should be administered 10 days later at temperatures between 48 and 58 degrees, but if the water temperature is above 58 degrees then this should be brought forward to 7 days.


Can be very troublesome if left unchecked, with the adults reaching 12 mm in length - it is greyish white in colour and attaches itself to the Koi by using hooks, or anchors as the name applies, boring into the skin tissue by first getting under a scale. Only the tail of the anchor worm is visible and looks like a short length of cotton. Anchor Worm needs treating quickly before a secondary infection.

Method of Eradication:-

The only known method of killing this parasite, without killing the Koi is DIMLIN POWDER which can be used safely at any water temperature and has an action of sterilizing the adult and larval stages of this parasite which insures that all eggs produced, after the application of Dimlin, will not hatch.

Method:- Dimlin Powder at the rate of 1 gram per ton of pond water. Measure out the quantity required and mix in a plastic bucket with pond water ensuring that the powder is dissolved then add to the pond in the previous manner. A second dosage may be needed to ensure that the life cycle of the Anchor Worm has been halted. After this second application the dead adults, which will still be hanging from the Koi, can be removed using tweezers but making sure that the hooks, as well as the tail of the Anchor Worm are removed and then apply a proprietary Topical dressing to prevent a secondary infection.

There is another way of removing Anchor Worm but more care has to be taken to remove all parts of the Anchor Worm ... that method is.... mix a strong solution of Potassium Permanganate crystals of 1 gram into 25mls of hot water. Mix well until dissolved and then dip the tweezers into this solution prior to the removal of the Anchor Worm, once the solution touches the body the Anchor Worm releases its grip immediately and it can then be lifted clear of the Koi and the water, wipe the end of the tweezers on a clean tissue to remove all traces before attempting to remove another Anchor Worm. to


cause Ulcer Disease. Other parasites can transmit and cause ulcerations, but none so effectively as the pathogenic trematode, or FLUKE.


Assume that if you're treating bacterial infections, you also have concurrent infection with Flukes. The flukes are easy to diagnose with a microscope. However, they are also easy to treat with Potassium permanganate top


This is a ciliate protozoan that is perhaps the most effective parasite at causing FLASHING. Spiderweb lesions in the skin are also a key finding. Again, a microscope is the diagnostic effort of choice. Eradication

Trichodina usually clears well and quickly with salt. (Three pounds per hundred gallons, non iodized salt) but there is at least one Japanese strain which must be treated with Potassium to clear. Still, I recommend a fair effort FIRST with salt and then if the microscope tells you there're still Trichodiniid organisms on your fish, treat with Potassium. top Freshwater Ich Ichthyophthirius multifilis- is a killer of very small fish, and can cause "redskin" disease in the winter regardless of fish size. Look closely at gill tissue under the microscope to be sure to exclude this pathogen, because it does not usually cause the typical "white spot" syndrome as in other fish. Therefore, it's often an overlooked diagnosis.


Clears easily with Salt (0.3%) but sometimes takes four to five days because the epidermal phase is safe from treatment. top


Chilodonella - "Killer Don" as referred originally by Dr. Jack Gratzek - this is the one that kills so many fish so fast in the Springtime.


Treats easily with salt, never seen an exception. Clears almost overnight, so salting can save the lot of fish. top

Anchor worm - Lernea elegans.

If you can *see* the parasites - you can kill it with Dimilin.


The Dimilin is a gyrase inhibitor added directly to the water, is non toxic to fish and clears this chitin-synthesizing parasite within three to four days. Pull off the Lernea if it's easy, or leave them on - whatever - but be SURE to treat with Dimilin, instead of wasting precious time and taking undue risk with organophosphates. top

Argulus - Fish Lice - this crustacean parasite is common especially in the Autumn for some reason.


Here again, if you can see the parasite, you can kill it with Dimilin. It's wonderful stuff but sometimes hard to get. top


Bacterial infections may take the form of at least five different conditions.
  1. Mouth rot
  2. Body sores
  3. Fin Rot
  4. Sudden Death
  5. Redbelly
  6. Pinecone Scales.
Bacterial infections are generally the result of several different stressors. A Stressor is a condition which causes the fish to have to adapt - such as:
  1. PARASITES (the number one cause of Ulcer Disease)
  2. Cold water
  3. Winter's starvation
  4. Crowding
  5. Crappy, corn-based diets.
Dropsy is the condition in which the body is diffusely infected with bacteria and the scales generally stand out from the body. In some cases, this is also caused by Costial infection (see parasites) but usually it's a terminal result of the bacteria attacking the KIDNEY of the fish. Many treatments have been tried with only a one-to-five percent favorable outcome. Dropsy, also known as Bloater or Pinecone disease, is usually caused by bacterial invasion of the fishes' kidney.

There IS a sporozooan parasite that can damage the Kidney this way, called Mitraspora cyprini, but I have yet to see this on a necropsy. Dropsy is, for all intents and purposes, untreatable, based on 7 years experience, using the following drugs: Azactam, Baytril, Chloramphenicol, Gentamicin, and Amikacin. I have tried a Sulfa drug, brand name Albon, and that did not resolve the problem either. top

Bacterial Dropsy

Bacterial Dropsy is usually caused by Aeromonas or Pseudomonas bacteria. By the time the fish "blows up" and the scales protrude form the body, the damage to the kidney is so profound that recovery is impossible. If you must try to save the fish, Isolate the specimen, elevate temps while elevating oxygenation, and begin injecting antibiotics intraperitoneally. You could also feed the antibiotics in a medicated feed. top

Ulcer Disease

Ulcer disease is almost always caused by Aeromonas bacteria or more rarely Pseudomonas bacteria. Clinically, I wouldn't know which because I rarely culture the pathogen. Why not? Because the results could take a week to return, and by that time, all the affected specimens would be dead. I have treated ulcer disease with the following drugs: Enrofloxacin, Chloramphenicol, Gentamicin, Amikacin, Tetracycline, and recently, Azactam. I inject these drugs.

No discussion of this problem would be complete without reference to swabbing techniques, antibiotic enriched feeds, injection technique, and prognosis. That to save these fish, my core recommendations would be to get the fish into a heated environment, provide impeccable water quality, swab the wounds with Iodine or Mercurachrome, Feed Romet feed, Inject Enrofloxacin and or Chloramphenicol, and hope that the next spring that the fish does not bloat due to retention of latent bacteria in the kidney after clinical cure. top


Sepsis is a condition wherein bacteria, mostly of the gram negative classes, gain entry to the fishes' bodies via wounds or the gut. In either event, the bacteria can cause the failure of the internal organs, and can result in symptoms which you might recognize: Clamped fish, bulging eyes, red bellies, reddened, eroding fins, etc. The problem with these types of cases is that the bacteria are inside the fishes' body and thus are quite safe from most water borne antibiotics. Therefore, feeding antibiotics, or injecting antibiotics are better choices than adding antibiotics to the water. top


Before Costia kicks everyone's rear-ends, please read the following. There are a lot of Japanese style shows going on, and the aftermath of several over the last twenty four months has read the same: Fish are mixed, returned home, novices do not take precautions, Costia kicks their butt so bad it looks like a "virus" until it's accurately diagnosed and cleared. top

The Significance of Costia

Life was simple for a fish vet in the early nineties. Japanese fish were too expensive for the average hobbyist and their beautiful wiles had not been fully discovered. The usual pond-call involved a poor filtration system, high ammonia levels, a sagging pH and a case of "garden variety" Trichodina on some hardy domestic fish.

One would simply recommend a treatment of salt coupled with an upgrade to the filtration type and flow. A week later, all the fish are recovered. Now, partly because exposure is more widespread and Japanese fish are so much more prevalent, the fish veterinarian sees much more challenging things. top

Salt Resistance

Salt resistance has arisen in the following parasites: Flukes - 20% of cases are completely resistant to salt treatments at any level. Most cases are cleared at zero-point-nine-percent but less than thirty percent still clear off at the old zero-point-three-percent standby level.

Trichodina - 20% of Trichodina cases do not clear at even zero-point-six-percent. There are rare cases where Trichodina does not clear even at zero-point-nine-percent which is also stressful to the fish. Formalin or potassium permanganate are recommended. Chilodonella and Ich have never been recorded as being salt resistant in the least bit.

Costia has shown some resistance and it is part of the reason for this article. Some outbreaks of Costia have been known to be salt resistant for at least two years. I saw my first case of salt resistant Costia in late 1996. top