A minifridge at the Staten Island Zoo holds the difference between life and death: thousands of dollars worth of snake-venom antidotes.

Once home to the most complete rattlesnake collection in the world, the zoo is trying to make a comeback one slithery reptile at a time.

And for every new species it acquires, it must have the right anti-venom – costly but essential should anyone be bitten by the deadly creatures.

“This vial alone was over $1,000,” said Matt Lanier, who manages the zoo’s snake collection, holding a tiny bottle of white powder.

It can take more than two dozen vials to counteract a bad bite – and the antidote must be administered within minutes.

There are alarm buttons between every padlocked exhibit, and a lightup panel shows which one was hit so staffers can secure the snake and grab the right antidote.

Car keys hang from magnets on the fridge door, ready for a dash to Richmond University Medical Center – which sent staffers to tour the zoo.

“From the time I hit that alarm button we are at the door to the emergency room in under seven minutes,” Lanier said.

Antidotes are created by injecting a small amount of venom into another animal. It isn’t harmed but produces anti-bodies, which are extracted from the blood.

Nobody has been bitten at the zoo for more than a decade, and the most recent nip was not serious – but the potential is always there.

Lanier admired a spitting cobra on display behind glass. “She can spit venom at your eyeballs from well over 6 feet away, and she’s deadly accurate,” he said.

A Mojave rattlesnake has two kinds of venom: hemotoxins that can destroy the limb that’s bit, and neurotoxins that shut down major organs.

“Beautiful, though, right?” Lanier said as one rattled its tail and flicked its long, black tongue.

The zoo was once renowned for its snake collection. In 1964, it was the first in the world to exhibit all 32 varieties of rattlesnakes native to the United States.

“The reputation of the zoo really soared,” said head curator Peter Laline.

After the driving force behind that collection, legendary snake expert Carl Kauffeld, died in 1974, it slowly dwindled.

The small, 8-acre facility is hoping to relive the glory days by acquiring rattlers from other institutions around the country.

They’re shipped as air freight, tied in pillowcases inside wooden crates. They must be quarantined for three months before going on display.

“We would love nothing more than to be able to say we have every species and subspecies out there,” Lanier said.

He fawned over a pair of new Eastern diamond rattlesnakes, the largest venomous snake in North America. One is a rare albino with pale yellow scales that wouldn’t survive long in the wild without camouflage.

The zoo now has 22 species and subspecies of rattlesnakes, and officials hope to mount field expeditions to track down the rarest specimens. Many will be part of the Rattlesnake Ridge attraction, which mimics the environment of the Sonoran Desert and opens in January.

“We’re going to be in here with a dozen to 15 rattlesnakes crawling around us,” Lanier said with relish.

“It’s going to give the public a chance to see how a field biologist would work with snakes in the wild, how they handle snakes safely,” Laline added. “It’s like an art form.”