koi anestesia

How to anesthetize a koi ? What is anaesthesia ?

How to anesthetize a koi? What is anesthesia?

The word anesthesia comes from the Greek and means “insensitivity“. It is a reversible pharmacological coma. It consists of blocking the tactile and pain sensitivity during a certain time with the help of an anesthetical product.

The anesthesia of a koi is proceeds as follows:


  • Phase I: Loss of balance
  • Phase II: Body immobilization with ventilation
  • Phase III: Body immobilization and ventilatory stop



  • Phase I: Light body immobilization with slight ventilation
  • Phase II: Start of body mobilization and regulate ventilation
  • Phase III: Full recovery of balance

Water temperature is an important parameter in all phases, both induction and recovery. An experiment* shows: The time to reach Phase II is reduced by 50% in water of 26 degrees instead of 15 degrees.

Also keep in mind that the induction and recovery time is higher with large koi than with small koi.


Nevertheless we in Koi Hacienda have noticed, that every koi is a different case. You can have big koi which “fall asleep” quicker than a small koi just because its constitution is different.

Why and for what anesthetize a koi?

Anesthesia is to do when we need to treat a koi and we can not allow it to move or to suffer. That happens when we have to heal wounds, do an X-ray or some kind of surgery etc. It may also be necessary to make a brief anesthesia if you want to make a detailed routine inspection of koi with preventive reason.


How to anesthetize a koi?

The most used products are phenoxyethanol and essential oil of cloves.


It is a good general anesthetic. There are two disadvantages: First, it is difficult to get this chemical product as a private person and second it is usually only sold in large quantities (1 liter to approx. 50 €).


  • 0.6-1 ml for 1 liter

Eessential oil of cloves

It is undoubtedly the most efficiente, inexpensive and easy product to get (in drugstores or online). Eugenol is an oily yellow liquid extracted from certain essential oils that can be used as an antiseptic and analgesic. Eugenol is also found in cinnamon, basil, laurel and many other plants, but only clove comes to be between 70-80% of eugenol.

As it has a low solubility in water, it is usually mixed with 96% ethanol in equal parts.

You can find essential oil of c clove of many brands. Prices range between 3.50 € and 15 € for a bottle of 10 ml or 15 ml. When buying, make sure that the eugenol concentration range between 70-90% (to ensure a good quality and to follow the recommended dosage).

Although most essential oils have dropper, it is safer to use a syringe and measure the amount in ml, as droppers do not have standardized amount.

koi enfermo


  • 2-8 ml to 100 liters (20-80 ppm)
  • 4 ml per 100 litres is considered optimal
  • less than 2 ml per 100 litres has no analgesic effects
  • more than 12 ml per 100 litres is fatal

In natural medicine it is used for its benefits in relieving digestive diseases, muscular, respiratory and skin. In this respect there are still no studies with fish.


How to anesthetize a koi – step by step

  • prepare a container with enough water (the full body of the koi must be under water) and the respective dose of analgesic
  • if you don’t use pond water, ensure that there is no important temperature difference between the water in the container and the pond
  • catch the koi and introduce it into the container
  • observe how the koi lives the different stages of induction of anesthesia. Do not leave the koi unobserved
  • when the koi has reached Phase III (floating, not breathing and no tactile reflexes) you can take it out of the water to make the necessary treatment
  • in the case that the koi “wakes up” before completing the treatment, you can enter it again in the analgesic water (especially the gills) for a short time
  • completed the treatment, the koi is introduced into a floating net in the pond so it can recover. If you would release the koi immediately into the pond, the koi could get damaged by crashing against any object in the pond as it has not yet 100% recovered its natatorium balance.
  • at Koi Hacienda we have experienced that some koi enjoy human touch and like this special treatment: instead of letting it recover in the floating net – we keep the koi in our hands moving it slowly forward and backward causing the water flow opens the gills and water can more easily enter. Thus it recovers easier.
  • once fully recovered its natatorium balance, you can definitively release the koi


How to anesthetize a koi ? Here a video which shows the different phases of anaesthesia:



De la Gándara, F.; Raja, T. y García-Gómez, A.

Instituto Español de Oceanografía. Centro Oceanográfico de Murcia. Planta de Cultivos Marinos.

Carretera de la Azohía s/n. 30860-Puerto de Mazarrón (Murcia-España). e-mail: fernando@mu.ieo.es


Utilización del aceite de clavo, Syzygium aromaticum L. (Merr. & Perry), como anestésico eficaz

y económico para labores rutinarias de manipulación de peces marinos cultivados A. García-Gómez 1, F. de la Gándara y T. Raja

Planta Experimental de Cultivos Marinos. Centro Oceanográfico de Murcia. Instituto Español de Oceanografía. Ctra. de la Azohía, s/n. E-30860 Puerto de Mazarrón (Murcia), España. Correo electrónico: antonio.garcia@mu.ieo.es





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