Euthanizing with benzocaine? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 20 Old 04-25-2013, 10:45 PM Thread Starter
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Euthanizing with benzocaine?

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?

RIP fire eel
why did you think it was a good idea to keep going over the top of the tank
when you realized you couldn't breathe outside water?
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post #2 of 20 Old 04-26-2013, 08:24 AM
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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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post #3 of 20 Old 04-26-2013, 12:50 PM
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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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two cents
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post #4 of 20 Old 04-26-2013, 02:13 PM
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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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post #5 of 20 Old 04-26-2013, 02:59 PM
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Originally Posted by MoneyMitch View Post
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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post #6 of 20 Old 04-26-2013, 07:14 PM
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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post #7 of 20 Old 04-26-2013, 07:15 PM
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Had no idea that's how I've been doing it since the first fish I've ever done this too
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post #8 of 20 Old 04-26-2013, 07:19 PM
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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post #9 of 20 Old 04-26-2013, 07:25 PM
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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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post #10 of 20 Old 04-26-2013, 07:36 PM
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, 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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