WATERVILLE — Russell Danner, a Waterville veterinarian, is seeking a patent on a mixture of spearmint and wintergreen oils that he says will knock a fish out cold.

“That cool sensation that you get when you use a spearmint toothpaste, that’s really anesthesia of your taste buds,” Danner said.

And for animals that breathe water, like fish, crustaceans and amphibians, that same effect causes a loss of consciousness.

Danner, who bought the New England Animal Hospital in March, has worked for the state as a fish pathologist, and also teaches at Colby College.

While working for the state, he saw a problem. Fish need to be weighed for various purposes, most commonly by aquaculture operations that are tracking the growth and health of their animals.

“But you can’t weigh a fish in water,” he said. “A fish is designed to weigh nothing in the water. Out of water, they flop around. In order to weigh a fish, you have to knock it out.”

The chemical currently used across the country to anesthetize fish, called ethyl 3 amitobenzoate methanesulfonic acid salt, is dangerous to humans, so fish treated with it can’t be eaten for 21 days.

That means that in order to weigh and release a fish in the wild, the entire waterway would have to be closed down for 21 days to ensure that fish bearing the chemical weren’t caught and eaten.

By contrast, spearmint is benign, and can be found in any grocery store.

Danner worked with students at Colby to come up with the right mixture of natural oils to do the trick. He tried cloves, oranges, and cinnamon, each of which worked to some extent, but had drawbacks.

He’s now satisfied that he has it just right, after having tried the mixture on minnows, trout, salmon, catfish and even lobsters and sharks.

The amount of spearmint needed to knock out a fish is tiny, he said, less than what’s in single stick of gum.

“I’m trying to figure out how to knock a fish out with an actual stick of gum and a glass of water,” he said. “It’s a parlor trick I haven’t quite mastered.”

One pound of Danner’s product, Fish-Eezzz, is enough to treat 80 gallons of water, which has the power to knock out thousands of fish.

Fish that are put into a bucket of treated water fall asleep in four minutes, going belly-up. Four minutes after they’re put back into fresh water, they wake up and swim off.

The patent has been in the works for nearly two years, he said, and should be approved within the next month or two.

Danner is working with the Food and Drug Administration in an effort to bring his product to market, but he said that he has been stymied so far.

The federal entity considers Fish-Eezzz a blend of two independent pharmaceutical agents which must undergo testing in human trials, both independently and combined. Each of the three trials would cost about a million dollars, Danner said.

Considering the ingredients in question, which have been consumed safely for thousands of years, he is trying to have the testing requirements dropped.

“Scientific validation needs to be tempered by common sense,” he said.

In the meantime, he is selling Fish-Eezzz as a neutraceutical, the same category that many vitamins and holistic remedies fall into.

He won’t be allowed to make medical claims, but he can say that it “relieves stress while handling.”

He also doesn’t expect to make a lot of money on the product, but hopes it will pay itself off.

Danner said that if his patent is approved it will continue a family tradition of creating useful inventions.

His grandfather developed a telephone answering machine, he said, while his father invented an interface that allows computers to answer phone calls.