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.