Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Treating wounds on larger fish

The equipment list for this treatment
The equipment list for this treatment



Make preparations

Make sure that you have everything that you are likely to need and put it where it is within easy reach.

Whilst the Koi should be treated carefully and without rushing, because it is out of water it is important not to waste time needlessly because something has been forgotten at this stage.

The equipment list for this treatment was:

  1. A large net.
  2. A large bowl where the fish can be anaesthetised.
  3. A clean non-absorbent soft surface on which to treat the wound. It is important that wet towelling isn't used because even when wet it will remove the fish's protective mucus coating. Wet polythene is a much better surface.
  4. The anaesthetic.
  5. The medication and something to apply it with.

Once everything is in place the next stage can begin.


The anaesthetics should be measured out very precisely. The anaesthetic in this case was one which is sold over the counter without the need for a prescription.

If you have difficulty obtaining this, the book Interpet-Fish Health states that Eugenol (oil of cloves) will work perfectly well when used at 10 drops per litre. And it has the advantage of causing numbness along with the sedation.

Which ever anaesthetic is used it should be carefully measured out and put in the bowl which has been pre-filled with water from the fish's tank/pond. Once the two solutions have been properly mixed (in the case of Eugenol this is quite difficult because it doesn't readily dissolve in water) we should just double-check the surface is laid out properly, that everything is to hand, and everything else is cleared out of the way. Once this has been done we can move on to the next stage and catch the fish requiring treatment.

measuring medication accurately

Catching the patient

Catching the fish should be done as carefully as possible and causing as little stress as possible, because if the fish gets too stressed it may affect the performance of the anaesthetic making it much harder to sedate. Also the oxygen requirement of the fish will rise very steeply making it harder for the fish to recover afterwards. So use a large net and stealth, and whatever happens don't end up chasing the fish around with a small net until it begins to tire. If that happens it would be better to give up and postpone the treatment.

Minimising stress when capturing a fish for treatment

Fish in a container in order to administer medication


Which ever anaesthetic you use, it is vitally important that you follow the instructions to the letter regarding dosage and time of exposure to the drug. If you don't follow that advice you could very easily end up euthanising the fish rather than treating it, because an overdose of anaesthetic is very often lethal.

To avoid shocking the fish it is also important that water from the fish's environment is used so that it has the same chemistry and temp. of the water that the fish has just come from.

Once the fish has become sedated and is relaxed and lying on its side, it can be lifted out of the bowl and placed on the pre-prepared surface for treatment. If the anaesthetic has done its job the fish will not struggle or wriggle whilst this is done or at any stage of the treatment.

Use polythene not a towel as a working surface for treating fish


The fish is laid out ready for treatment. As predicted the fish is completely relaxed and makes no attempt to move, which is safer for the fish and makes treating it much simpler.

As an extra precaution the fish is covered and only the area requiring treatment is left uncovered. Hopefully this will reduce the stress to the fish even more.

It is important at this stage not to rush but instead work methodically and do everything that has to be done so that the process doesn't have to be repeated unnecessarily.

Whenever anaesthetics are used there is always a small risk involved no matter how careful you are.

Keep the fish covered as much as possible during treatment

The treatment to the koi has been applied

The wound can be clearly seen and is easily accessible. In this case it is what is left after the fish suffered from a deep fungal infection, and although the fungus has been successfully treated, the wound left behind was treated with a waterproof topical antiseptic which is made for exactly this type of situation and will prevent further complications from a potential secondary infection.

Once the treatment had been carried out the fish was given a quick but intense check over to make sure nothing had been missed.

It was then placed back in the net and held upright in the water near to a spray bar where it recovered within a matter of a minute.

Holding the fish until it recovers from sedation

The treatment was 100% successful and the wound healed quite quickly without the need for any more treatment. One year on it has remained perfectly healthy.

A fully recovered koi

The end result of a fully recovered and healthy fish, makes all the effort worth while.

See Treatment finder

Treating wounds

Sometimes, whether through injury or disease, it is necessary to treat fish with open wounds. This is simple enough with small community fish where the aquarium water could be treated or the fish caught and treated. When a larger much more powerful fish such as a Koi or an Oscar is the patient there is a risk of the fish putting up a violent struggle, risking further injury.