# Euthanizing with benzocaine?



## Freddy (Nov 17, 2009)

Hey everyone, sad news. :-(
My last angelfish has an unknown disease. It seems like fin rot, but it's on his gills and there's a hole in the skin covering them that grows a little bit every day. The disease isn't responding to treatment, so it looks like I'm going to have to euthanize him. I researched it online, and found that the preferred method is to put the fish to sleep with clove oil, then to either deliver a lethal overdose of clove oil or to add in alcohol (presumably any toxin will work at that point). However, clove oil is incredibly hard to find around here. It's used in treating toothaches, but the closest thing I can find is liquid benzocaine. The articles and forum posts I found said that benzocaine hydrochloride was preferred, since straight benzocaine isn't water soluble, but the hydrochloride variant is not available to the public. So, I'm left with two (humane) choices, and one questionably humane choice: the two humane choices are, either use the clove oil process with benzocaine (will that even work?), or to immerse the fish in almost frozen water. There's also the option of putting the fish in a bag and smashing it on something hard... but I'd REALLY rather not have to do that. The frozen water technique seems to work pretty well; we had a bass in the 90 gallon tank and released it into the wild when we moved in my oscars. Unfortunately, the water was much colder than we thought, and the bass was knocked unconscious, even after being acclimated for over 10 minutes in a bucket. There was nothing we could do after that.
So, it's benzocaine or (almost) ice. Will benzocaine work?


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## Tazman (Jan 15, 2012)

clove oil and vodka is about the most effective humane method.

It puts the fish to sleep and kills them quick.


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## twocents (Feb 22, 2010)

there is also a product called 'Finquel' which I got through dr foster (I think). It will euthanize, it is used to sedate fishies, so they will wake up. 
I have this product at home and I have used it several times, and am probably going to have to use it again, soon..if I can catch the pleco.


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## MoneyMitch (Aug 3, 2009)

personally when it comes to euthanizing fish this is going to sound harsh but its how I do it. net them up and then give them a good smack on concrete or something hard. its instant and they don't feel a thing. ive done this to many fish that ive been close to in the past. was easyier then watching them suffer but at the time never thought of a chem to do it.


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## jaysee (Dec 9, 2009)

MoneyMitch said:


> personally when it comes to euthanizing fish this is going to sound harsh but its how I do it. net them up and then give them a good smack on concrete or something hard. its instant and they don't feel a thing. ive done this to many fish that ive been close to in the past. was easyier then watching them suffer but at the time never thought of a chem to do it.


Hahaha, that being said, my preferred method for small fish is the garbage disposal. I turn it on with the water running, and poor the fish in from a cup. I don't think anything is more humane than being obliterated into a thousand pieces in a second. And, there's no clean up. In my opinion, humane = instant death. I'm sure some will have a problem with this method, or any method that is "brutal" for that matter, but that doesn't change it's effectiveness. However, for me, it is silly to be concerned about killing fish "humanely", since I work on a fishing boat. I do provide my fish the courtesy that I do not extend at work though. If I worried about it at work, people would think I was a nutcase....

Along the lines of MM's method, is the hammer method. Put the fish in a paper towel and hit it with a hammer - instant death, easy clean up. With large fish, these methods are just not practical, though.


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## Sakura8 (May 12, 2011)

Just a note, Moneymitch. When using the blunt trauma method of euthanization, it needs to be followed through with decapitation and then piercing of the brain. I know, sounds gross and cruel, but unless the brain is totally destroyed in the act of blunt trauma, it can live on for hours after the rest of the fish has passed. The fish brain is very resistant to hypoxia. 

If you need my sources for this, I will post them.

EDIT: I use Finquel. It works very well for euthanization, better than clove oil in my opinion. Only thing to remember when using it is to add baking soda because Finquel causes a drastic pH crash that can make the end that much more traumatic.


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## MoneyMitch (Aug 3, 2009)

Had no idea that's how I've been doing it since the first fish I've ever done this too
_Posted via Mobile Device_


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## Sakura8 (May 12, 2011)

Most likely the fish didn't feel anything and did die during the blunt trauma but there's that slight chance the brain lives on afterward for a few hours. :/

Don't worry, most people don't realize this about fish. I didn't, until I started reading up on it.


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## twocents (Feb 22, 2010)

sakura, there has never been any thrashing with finquel. don't really think there is any reason to add baking soda


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## Sakura8 (May 12, 2011)

Interesting. I went through the Finquel pamphlet and you're right, it says nothing about baking soda. However, the website I used for dosage information said to use baking soda.

Mini Aquariums: Humane killing (euthanasia) of aquatic pets (under construction)

In addition, fishchannel.com had this to say:


Aquarium Fish Euthanasia
Euthanizing and disposing of aquarium fish.
By Neale Monks, Ph.D.

*Anesthetic Overdose
By administering an overdose of an anesthetic, vets can ensure that large fish are humanely euthanized. This is the method recommended for use with large fish, such as koi, oscars and saltwater angelfish. Because large fish will be stressed by being caught and transported to a veterinarian, the vet may need to visit the fishkeeper’s home and euthanize the fish there.

A variety of anesthetics have been used for this purpose, including 2-phenoxyethanol (bath, 0.3 to 0.4 mg/liter); benzocaine hydrochloride (bath, at least 250 mg/liter); sodium pentobarbital (injection, 60 to 100 mg/kg body weight); tricaine methanesulphonate, also known as MS222 (bath, 300 mg/liter). Because tricaine methanesulphonate is acidic, it will need to be used alongside an appropriate pH buffer. You need a pH buffer if you have fish from a non-acidic aquarium. Taking a marine fish from an aquarium at pH 8.5 and dumping it into a bath containing MS222 solution at around pH 6.5 will be intensely stressful. So if using this chemical, buffer the water to the correct pH before adding the fish.

It may take more than 30 minutes for death to occur, and it is recommended that fish be left in anesthetic baths for at least 2 hours to be sure. Death will need to be verified before the fish is removed.*

So perhaps you didn't have any thrashing because your tank is already acidic? Mine isn't, it's quite alkaline so I used baking soda.


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## twocents (Feb 22, 2010)

finquel is so fast, I still don't think there is a problem..but then, I've never used it on a large fish


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## Sakura8 (May 12, 2011)

It was a betta and yes thankfully, Finquel is very fast. I was grateful for that. Most likely you are right and there wouldn't be a problem but I had the baking soda on hand and it didn't hurt to try it.


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## twocents (Feb 22, 2010)

the old adage applies: better safe than sorry.. and if it can perhaps ease the passage more, all the better..


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## Byron (Mar 7, 2009)

I just happened to come across this article today on the subject.

Painful fish deaths? You might be guilty


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## Sakura8 (May 12, 2011)

Very informative, Byron, and definitely sheds some light on the controversy of fish euthanization. It does support the theory that Finquel, which is MS-222, causes the water to be highly acidic and therefore a buffer is needed. Interesting that Finquel itself does not mention this in their extensive pamphlet which accompanies the jar.


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## Pep (Dec 29, 2009)

How about where it is next to impossible to catch fish to net them without causing massive stress by chasing them all over a tank? my tank is winding down as the fish have slowly died off from old age but I have 3 fish left and they are starting to show signs of a disease. All of them are older. I hate to see them in pain and would like to put them out of their misery but tried catching them but couldn't. Any suggestions on euthanizing them in the tank?



Byron said:


> I just happened to come across this article today on the subject.


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## Byron (Mar 7, 2009)

Pep said:


> How about where it is next to impossible to catch fish to net them without causing massive stress by chasing them all over a tank? my tank is winding down as the fish have slowly died off from old age but I have 3 fish left and they are starting to show signs of a disease. All of them are older. I hate to see them in pain and would like to put them out of their misery but tried catching them but couldn't. Any suggestions on euthanizing them in the tank?


I would definitely net them out first. A "quick" death is next to impossible in a tank. Plus, putting any substance in the tank to kill the fish would almost certainly make the tank useless for any future fish, as the substance would permeate everything, substrate, wood, rock, the silicone perhaps, filter... not a good idea.


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## jaysee (Dec 9, 2009)

Pep said:


> How about where it is next to impossible to catch fish to net them without causing massive stress by chasing them all over a tank? my tank is winding down as the fish have slowly died off from old age but I have 3 fish left and they are starting to show signs of a disease. All of them are older. I hate to see them in pain and would like to put them out of their misery but tried catching them but couldn't. Any suggestions on euthanizing them in the tank?


I find that removing the water makes fish much easier to catch.

Though, if you are unable to catch the fish, then perhaps they are not yet at the point that they should be culled.


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## Pep (Dec 29, 2009)

Well, I am not too worried about substrate or wood as it will all be coming out. But the silicone is a good point. 

and lowering the water level I was thinking of and will have to do it that way. The 3 red lines are old and hurting but still pretty darn fast when stressed with a net in the water. Thanks for the info.

I need to try to find some finquel now as I like that idea. BigAls online in canada doesnt have it. :-?



Byron said:


> I would definitely net them out first. A "quick" death is next to impossible in a tank. Plus, putting any substance in the tank to kill the fish would almost certainly make the tank useless for any future fish, as the substance would permeate everything, substrate, wood, rock, the silicone perhaps, filter... not a good idea.


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## twocents (Feb 22, 2010)

unless you are going to mothball the tank, you could pump the water out into a container, and once you have caught all the fish. put it back.


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