
Originally Posted by
SkeletalFrog
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).