Clove oil and eugenol
Clove oil or eugenol is an approved and safe fish sedative. Clove oil is made up of between 80 to 95 percent eugenol. Clove oil can be obtained from distillation of buds, leaf or stem.
For example, it is used with fingerling rainbow trout to get them handleable. In one study, test fish were safely exposed to the highest proposed efficacious dose (40 mg/L eugenol) and to a dose 1.5 times higher (60 mg/L eugenol) for several minutes longer than the time required to sedate these fish to handleable. Eugenol has been used with rainbow trout, yellow perch, channel catfish.
See this link for use with catfish: https://www.globalseafood.org/advocate/clove-oil-eugenol-effective-anesthetics-for-silver-catfish-other-brazilian-species/
Use of clove oil in fish sedation.
Clove oil is a good alternative as a fish anesthetic. It is e.g. relatively inexpensive and is generally regarded as safe for the user and for the fish. However it is light sensitive and recovery period after the anaesthesia may be long, especially in cold (<5°C) water. Sensitivity to clove oil may also vary between species, so it is advisable to test it before using it in larger extent.
How to use clove oil: with ethanol and without ethanol
Method 1:
- Prepare a solution of clove oil with ethanol (94%): 9 parts ethanol + 1 part clove oil (1:10 clove oil ethanol solution). Keep this solution in a dark bottle, preferably also in the dark. Clove oil must be mixed with alcohol before use because it is insoluble in cold (<15°C) water.
- Use this solution to anesthetize your fish. If you do not have earlier experience with clove oil with the specific species, I would advise to start with the concentration of 30 to 40 mg/l. In practice this means that you add 2 ml of the solution into 5 l of water (4.4 ml of the solution were added to 10 litres of water to give a 40 ppm solution). You should be able to immobilize the fish within about 3 minutes.
- Exposure of longer than 15 min may prolong recovery times and increase mortality; especially if higher concentrations are used.
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Clove oil, has also been reported to have anti-bacterial, antifungal and anti-oxidant capabilities.
(Clove oil is a dark-brown liquid, a distillate of flowers, stalks and leaves of the clove tree Eugenia aromatica. Clove oil is also distilled from stems, leaves and flower buds of Eugenia caryophyllata, and its active ingredient, i.e. eugenol (4-allyl-2-methoxyphenol), makes up 70 to 90% by weight)
On the basis of tests of acute toxicity to carp, the 10-min lethal concentrations of clove oil were determined (10 min LC50 74.3 mg/l, 10 min LC 0.1 51.6 mg/l and 10 min LC 99.9 110.1 mg/l) (ref: vri.cz).
Method 2 – without ethanol:
Use the full dose on koi 18 inches or more, for smaller koi of at least 10” I found 3 drops did the job. For koi smaller than “10 first experiment.
If you decide to sedate your koi for treatment or diagnostic purposes, and lose them please don’t blame me because you read this post. I’m posting this to hopefully help someone save their fish not kill them. We take no responsibility for the application of this advice.
Using Clove oil
Equipment: Bucket, pondwater, clove oil, dropper, ziploc bag or small jar.
You should place the fish in a 20 liter (five gallon) bucket with just over half (three gallons) of the fishes tank water. Make sure the bucket is aerated and cool. Have a second bucket ready with untreated water.
Use eugenol (100% eugenol) or clove oil (85% eugenol). Add five drops per gallon (after emulsification, see note below) into the bucket.
Emulsification: You have to emulsify the anaesthetic. Simply place the required number of drops of Clove oil into the ziploc bag or jar with a little bit of the bucket water, cap it, shake it until it becomes a whitish fluid, then pour this emulsion into the bucket with the fish. This method avoids the need for costly ethanol.
The fish should be asleep in about seven to ten minutes. You should still see gill movement. Sometimes it takes more or less depending upon temperature. The water should be aerated.
When the fish turns over on its side and gill movements slow, remove it from the solution, perform the planned procedure. If the fish doesn’t roll over in 5 minutes, then add another drop per gallon (shake it up in water before adding).
You need to WATCH the anaesthetic process and the fish! You can begin the handling and other procedure when the fish is still slightly active, but not actually capable of struggling when picked up. If you leave the fish in the oil mixture until gill movement ceases entirely, you have likely killed the fish. If gill movements become too rare, (less than five excursions per minute) then you should rinse the gills with fresh water from the tank. Failure to have someone watching the status of the fish is where most of them die. Then some fool blames the anaesthetic dose, and not the anaesthetist!!!
Taking fish to the brink of death is not easy with clove oil. You can dose them with 100x overdose for fifteen minutes and lose only a few of the fish. Deliberate attempts at humane euthanasia with Oil of Cloves are sometimes not successful. The fish revive after being placed in fresh water for up to two hours. Never give up on a fish which seems to have “died” under anaesthesia with this very safe compound. (ref: www.koinet.net).
After you’re done place the fish in a bucket of clean water and return him to the tank.
You may need to hold the fish for a little while in an area where fresh water is moving through its gills (e.g. by the outflow of the filter) until he gets less groggy.
References
N. Nurdjannah, N. Bermawie, in Handbook of Herbs and Spices (Second Edition), Volume 1, 2012
11.2.3 Clove oil