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Advantages of dip treating Pond fish

The most obvious advantage to a dip treatment for any fish is that the exact dose of medication can be calculated, and the duration of exposure can be timed perfectly. Also, only those fish which are showing symptoms can be treated, leaving the healthier stock (who perhaps have a better resistance to the ailment), untouched by the medication. Some chemicals used to treat fish diseases can have dire consequences on the ecology of the pond or aquarium, thus they must be used in isolation. Some treatments work well on mild infections when applied at a low dose to the pond as a whole. However, when infection has progressed to a higher level, causing severe debilitation and secondary infection, the fish is often so weak it can no longer resist the infection by the initial infective agent. At this stage a stronger dose of medication is essential, and this can only be done through dip treatment.

Disadvantages of dip treating fish

The main problem with dip treating fish is that it treats the symptoms of a disease rather than the root cause of the problem. Only those infective agents on the fish at the time are eradicated. Many further parasites/bacteria/fungi etc, can still be present in the main pond. Some can be found in the sludge and detritus of the system, they can be found infecting other fish subclinically (without symptoms). Also many parasites and bacteria can form tough resistant cystic structures that lay dormant in the pond, waiting to re-infect when the fish are stressed. Thus a dip will rid an individual fish of an infection, but the pond as a whole may still harbour infective agents.

Protocol for dip treating Koi

It is wise to have a hospital system established, as subsequent dips are often required, and the fish's recovery can be closely monitored. If this is not possible, a recovery bath containing pond water should be made. Prepare the dip bath; add a known volume of water (preferably pond water, but if dipping in Potassium Permanganate use tap water dechlorinated with CHLORGO),then add the required dose of the relevant medication, and disperse thoroughly in the bath. Catch the fish as quickly as possible and gently lower it into the dip. Start a stopwatch. Monitor the fish closely during the treatment. An adverse reaction usually involves the fish panicking and thrashing around in the bath, gasping and even trying to leap out of the dip. Leave the fish in the dip for the required time, and then remove it into the hospital system or recovery bath. Observe the fish for any ill effects, ensure the fish can maintain balance in the water.


This compound is a very strong antifungal agent, with marked antiparasitic and antiseptic action at higher concentrations. Most commonly used applied to the pond as a whole, frequently in conjunction with FORMALDEHYDE. Particularly stubborn cases of fungal infection can be treated by dipping the fish in a bath of 1 PPM MALACHITE GREEN (0.5 ml per UK gallon), for one hour. If infection persists a stronger 66 PPM (30 ml per UK gallon), for one minute can be employed. Ensure the infection is of fungal origin, as symptoms superficially resemble cotton-mouth (infection by the bacteria Flexibacter columnaris). MALACHITE GREEN can also be swabbed neat, directly onto fungal growths, and large macroparasites such as anchor worm or fish lice. However ensure none of the chemical enters the gill opening, as it is extremely irritant to fish gills at that strength.


Potassium Permanganate is a powerful oxidising agent that can be used to eliminate very wide range of pathogenic organisms. From the large macroparasites such as anchor worm and fish lice to the microparasites such as the flukes, Ich and Trichodina, cotton-mouth, fungus, Pseudomonas and Aeromonas bacteria, and many more. Fish with the early stages of ulcer disease respond very well to a dip of Potassium permanganate. The highly caustic nature of Potassium permanganate means it is a very effective treatment when used as a dip but, extreme caution should be taken when using it. Fish that have been subjected to an excessively high dose of the chemical should be bathed in milk, which removes all traces of the chemical. As a dip Permanganate can be used at 10 ml per 200 L (44 UK gallons - 53 US gallons) for 10 to 12 hours. If a stronger treatment is required, use 10 mls per 40 L (9 UK gallons - 11 US gallons) for 30 minutes. The chemical can also be diluted and swabbed directly onto fungus, and large macroparasites: Add 10 ml to 400ml water and dab the solution onto the offending agent with a cotton bud. These treatments should only be performed once. The presence of organic matter in the water of the bath will lower the effectivity of the chemical, as the oxidative energy is spent on the detritus, rather than on the fish. If the permanganate has lost its strength it will turn from the pink colour to brown. Thus if the pink colour subsides before the treatment is complete it may be necessary to add more chemical to restore the pink colour. When preparing a bath of permanganate, always use dechlorinated tap water, as this contains less organic matter than pond water. If a carbon block filter is available use water from here. Should too much chemical be added it can be deactivated by adding an equal quantity of Hydrogen Peroxide (3% solution). Chlor-Go or failing that a small amount of milk and then change some water.


Formaldehyde, like Permanganate is a very intense treatment to perform on a sick fish. Both are extremely effective, but the toxic dose for fish is quite close to the toxic dose for the invading pathogens. Thus you should only use these treatments if you feel sure that the EXACT dose can be metered out, and you feel confident you can recognise the signs of overdose in the fish. Formaldehyde is one of the few chemical medications that can actually penetrate the mucous layer of the fish and then kill the parasites inside. Most parasite infections will be cured by the addition of Formaldehyde to the pond as a whole but stubborn cases may require dip treatment. Use 5 mls of Formaldehyde per 10 L (2.1 UK gallons - 2.6 US gallons) for up to one hour, unless your water is extremely soft, then use 4 mls per 10 L. This treatment can be repeated every 3 days if required, but one treatment should suffice providing the fish is in a hospital system. Formaldehyde will lower the oxygen content of the water so it is wise to aerate the dip during the treatment using an airpump and airstone.


Salt is the simplest, most readily available, cheap, treatment available to Koi keepers. There are many myths surrounding its use, and its spectrum of activity. When used as a dip, salt will kill a wide range of microparasites (some strains of flukes and Trichodina are becoming resistant, and require higher dosing) Other beneficial effects of salt are that it reduces osmotic shock of wounded fish by lessening the degree of water uptake by osmosis. Salt is also a muco-stimulator, causing the goblet cells of the fish's epidermis to increase production of mucus, thereby sloughing off any invading pathogenic organisms, and also increasing the protective coating over any exposed ulcers. When using salt as a chemotheraputic agent ensure that it is either non-iodised table salt, water softener salt, sea salt, or preferably specialist Koi pond salt. A hydrometer such as the New Technology SALT TESTER is an essential piece of apparatus.

Although a known amount of salt has been added to a known amount of water, the actual salinity of the water will fluctuate; rising due to evaporation, or declining due to dilution by rainwater. Don't guess the amount of salt in the water - USE A SALT TESTER!

To treat external parasite infections use 0.5% (3/4 Oz per UK gallon) dip for 30 minutes. For large fish a 1% (1 ½ Oz per UK gallon) dip for 6-10 minutes can be used. In particularly stubborn cases such as Asian Trichodina, or certain serotypes of Dactyloyrus and Gyrodactylus, a 4 Oz per UK gallon dip for up to ½ hour may be required. To prevent osmotic shock in wounded fish use a long-term bath in a ½ Oz per UK gallon. Use this dose in a hospital tank where the salt level can be monitored and controlled. It is wise to start the therapy at half the above dose, and gradually increase to ½ Oz per gallon.


Acriflavin is a mild antiseptic usually applied to the whole pond to reduce the numbers of bacteria in the water. It is added at a mild enough dose not to harm the filter bacteria. Should a larger dose be required then the treatment must be used as a Dip. Acriflavin will treat bacterial skin infections, and help to sterilise infected wounds and ulcers. Use 16 mls of ACRIFLAVIN per L for 30 minutes. Repeat this treatment daily as required HYDROGEN PEROXIDE. This is available from chemists in a 3% solution. As a 15ml per L dip for 10 minutes it works well in ridding the fish of protozoan and fluke parasites. This treatment should only be used once. Hydrogen peroxide is also useful in deactivating Potassium permanganate, if there has been an overdose or the fish show an adverse reaction. Add an equal amount of Hydrogen peroxide to the amount of permanganate.

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