We all know itís not nice when we have to let go of one of our betas, but it makes it all the worse if we are the ones who have to put them out of their suffering.
The best way I have found in done in two steps
∑ Put the betta to sleep
∑ Make sure it doesnít wake up
This method is often thought of as mixing clove oil and vodka together. This is wrong. Clove oil must be used first, making the betta fall asleep before you add the vodka. Vodka will be very stressful for a betta if not anesthetized.
Eugenol (clove oil) is available at any pharmacy as a cure for toothache. It has been used for many years as an anesthetic for fish during tagging or surgery.
Clove oil puts the betta to sleep and makes sure it feels no pain. Be warned, the betta can still wake if taken out of the clove oil before drowning, by adding the vodka you are making sure the fish dies.
Here is how to euthanise a betta
1. Put the betta in a container of tank water but make sure to measure the amount of tank water and make a note of it. If it is a clear container please put a towel around it to calm the fish.
2. Fill a small jar with tank water but leave a gap at the top. Add 1 drop of clove oil to the jar, put the lid on and shake hard till the water turns a milky white, this means that the oil has mixed with the water. When it has turned white, place about ľ of the mixture in with the betta. The betta will begin to fall asleep, leave for about 10 minutes after this it will look dead, but if you watch closely it may be still breathing, if it still alive get the jar and shake again and add the same amount as before and wait again.
3. Once the fish has gone to sleep on the bottom, add 20-25% vodka, i.e. if the fish is in 8oz of water add 2oz of vodka, leave the betta in there for at least 20 minutes
4. After 20 minutes check for gill movement, if you donít see any within 60 seconds, the betta has died.
It is not essensial to add the vodka with betas as they are air breathers; this means that when they are asleep in the clove oil they would just drown peacefully. I use the vodka for my own peace of mind.
Another method is an anesthetic called Tricaine Methanosulphate (TMS). 1g of TMS in 1 liter of water makes a bath that will put the betta to sleep peacefully.
What not to do.
∑ One very popular way people suggest is to put the betas in the freezer, where it is said to go slowly to sleep and die without suffering. Obviously someone who has never felt the pain of truly being cold started this. What actually happens is the betta will live for quite a while because it is such a slow method? During this experience a very high level of stress and pain as the cells in itís body slowly by ice crystals forming in their organs, until too many cells are damaged for the betas life to continue.
∑ Never flush a live betta down the toilet as this is very cruel, because the fish may survive a long time
∑ Do not simply take the betta out of water and wait for it to doe as they are air breathers, they will take along time to die by dehydrating.
∑ Do not drop into hot or cold water since both take a while to work. Both also cause pain and suffering.
The above examples are horrifically very common. Do not under any circumstance use any of these.
British Veterinary Zoological Society
Guidelines for Acceptable Methods of Euthanasia for Zoo, Exotic Pet and Wildlife species
British Veterinary Zoological Society [BVZS], 7 Mansfield Street, London W1M 0AT, UK. http://www.bvzs.org
No. 2: Ornamental Fish
There are many situations where euthanasia (humane destruction; 'putting to sleep') of an animal is necessary. It is essential to the animal's welfare, and a legal requirement, that the method chosen does not cause unnecessary suffering. This document gives Veterinary surgeons and others suggestions on current acceptable methods of euthanasia. The guidelines are for informational use only. They are not exhaustive. Other methods may occasionally be applicable.
Euthanasia of fish is a difficult task to those not accustomed to treating these species. Problems arise mainly because of unfamiliarity of the anatomy (which limits access to sites for injection) and physiology (different response to anesthetic drugs). It is difficult to ascertain with certainty that a fish is dead rather than heavily anaesthetized (complicated by the possibility of slow metabolism of anesthetic drugs).
Suggested methods of choice:
The following methods are rapidly effective and straightforward to perform.
∑ Overdose of a soluble anesthetic agent added to the water (MS222, Benzocaine [in acetone /alcohol], Eugenol [clove oil])
∑ Intravenous overdose of anesthetic agent, primarily pentobarbitone.
∑ Trauma sufficient to induce complete and instantaneous loss of brainstem activity (e.g. shooting, captive bolt, massive blunt trauma, cervical dislocation or fracture)
∑ Dropping into liquid nitrogen to provide near instantaneous complete freezing (individuals less than 1cm max diameter only)
Methods acceptable if methods of choice not possible:
These methods are effective, but involve a prolonged (hours) delay before the animal can be pronounced dead.
∑ Intracoelomic overdose of pentobarbitone
∑ Some methods used in commercial fisheries
Methods considered unacceptable:
The following methods have been suggested for ornamental fish euthanasia in the past but should now be considered ineffective or unacceptable:
∑ 'Asphyxiation' (simple removal from water preventing respiratory exchange)
∑ Freezing (excepting method suggested above)
∑ Use of other anesthetic agents added to the water (Pentobarbitone, Isofluorane, Halothane)
∑ Trauma (other than cranial & cervical trauma as described above)
∑ Carbon dioxide by non-commercial methods (Alka-seltzerģ tablets, soda-streamģ carbonation)
Death (loss of brainstem activity) is difficult to confirm in fish.
Suggested criteria to evaluate include:
∑ Lack of external reflexes (Movement, response to external stimuli)
∑ Lack of detectable respiratory activity (no spontaneous opercular movements)
∑ Lack of detectable cardiovascular activity (Doppler ultrasound, ultrasound, ECG)
Fish which are heavily anaesthetized will have few, if any, outward signs of activity and appear dead by the criteria above yet may regain consciousness (after, e.g. metabolizing or excreting anesthetic drugs).
Methods of ensuring a fish does not regain consciousness include:
∑ Do not return a fish anaesthetized by in-water methods to fresh water. Leave it in the euthanasia solution or wrap it in towelling soaked in euthanasia solution to maintain anesthesia until death occurs.
∑ Inject a massive overdose of intracoelomic pentobarbitone once unconsciousness has occurred.
∑ Once the animal is unconscious and insensitive to external stimuli, perform pithing (physical destruction of the brain tissue) or freeze the carcass.
Information with thanks to
British Veterinary Zoological Society
Fish, tanks and ponds
Edited by red-devil0602, 19 October 2005 - 08:51 PM.