Quote Originally Posted by SkeletalFrog View Post
Definitely do not freeze him. Freezing is not a humane method for the euthanasia of reptiles or amphibians.

Your best option is to go to any specialty aquarium store (not a chain like Petco), and ask for anaesthetics. There are 3 standards - Metomidate (marketed under "Aqua-calm"), MS-222 aka tricaine (marketed under "Finquel"), and Eugenol aka clove oil. Any will work, and you can just call any aquarium store and ask for them by these names.

There will be directions on the bottle of each for anesthesia and euthanasia of fish, but because frogs don't have gills, I recommend increasing the euthanasia dose by five times or more (after all, more won't hurt). Just mix as directed, put the frog in, and wait for an hour or so.

Because they're anaesthetics, the frog will just gently go to sleep, just like what happens with dogs and cats at the vet (though the vet uses a chemical not available to the public).
When these particular frogs start to get cold, they tend to go into aestivation.......they go to sleep. Freezing, in my opinion is just as viable as the methods mentioned here. It has the same effect, and in all honesty, takes less time to do the job. Frogs do not react the same as fish do to these anesthetics. I have seen this myself....the frogs don't always "just go gently to sleep".......they sometimes will have seizures as a reaction to the drugs. With freezing, they do simply shut down. They go into aestivation mode before the cells start to freeze and the whole process takes less than an hour. In the end, it is your choice as to which method you use.