A fanged coral reef fish that disables its rivals by delivering a dose of heroin-like venom could one day cure your pain, researchers say.

Researchers have found the fast-acting venom of the fang blenny, found on the Great Barrier Reef, is "chemically unique", raising the potential for the discovery of novel painkillers for use in human medicine.

"We have never seen a venom acting this way," said venom researcher Bryan Fry, of the University of Queensland. "It's completely novel."

It is rare for a defensive venom not to inflict pain as a way of disabling predators or rivals. Fish in particular are known to have agonisingly painful venom. However the fang blenny venom acts on the body's opioid receptors, like heroin or morphine. Instead of causing pain, it makes its rival slow and dizzy - and less of a threat.

This allows the fang blenny to either see off potential predators or snap up the best bit of real estate on their patch of coral reef.  

"These fish are little jerks basically," Associate Professor Fry said.

The striped fish grow no longer than 10 centimetres and are popular aquarium fish.

Also known as poison-fang blennies or sabre-tooth blennies, the pugnacious tropical fish have a venom that only temporarily impairs, with the effect wearing off within a few hours.  

A CT scan of a fang blenny reveals venom glands are connected to oversized fang-like teeth in the fish's lower jaw, which are hidden from view by the animal's lips.

"The fangs are big, certainly for their body size," Associate Professor Fry said.

However, the opioid peptides in the venom are small, which in theory mean it is easier for scientists to make a synthetic version capable of being quickly absorbed by the body.  

"What's interesting is that these peptides are identical to our natural painkiller ones," Associate Professor Fry said.

Lizard Island on the Great Barrier Reef has historically been a stronghold for the fang blenny fish in Australian waters. However, it is also one of the areas worst affected by coral bleaching. Associate Professor Fry said this was a reminder of what was at risk of being wiped out.

"These guys are an example of what could be lost," he said. "And why we should protect what we have got, because you never know where the next blockbuster painkiller drug will come from."

The research by scientists from Australia, Britain and the Netherlands will be published in the journal Current Biology on Friday.