The Irish Society for the Prevention of Cruelty to Animals has warned that eating live goldfish is a criminal offence.
It issued the warning after a video appeared on Youtube purporting to show a woman putting a live goldfish into an alcoholic drink before swallowing it as part of a Neknomination challenge.
The ISPCA said it had received a number of calls about Neknomination videos in which it appeared that goldfish were being swallowed alive.
It said the videos are under investigation.
Chief inspector Conor Dowling said in a statement this morning that: "This is one more reason, among many, why there should be great concern about this phenomenon.
“Eating any live animal and posting it on a social media site is not funny. It is unacceptable and is sending out a message that animal cruelty is okay”.
It is understood the woman involved in one of the videos is from Northern Ireland. A number of reports were submitted to police in the North.
A spokesman for the PSNI said it had been notified about posts on social media but said it was not following up on the issue as it understood the events took place outside its jurisdiction.