Chinese animal rights groups are urging TV stations not to show a magic trick of goldfish swimming in formation.
They believe the performance could involve the use of magnets and therefore harm the fish.
Campaigners want the act dropped from variety shows to be broadcast on Thursday to mark the end of the Chinese New Year holiday.
The magician at the centre of the controversy, Fu Yandong, denies he harms the fish.
The trick has amazed audiences across China, appearing on one of the biggest shows of the year, China Central Television's New Year's Eve special.
Mr Fu takes six goldfish and releases them into a shallow tank. He somehow gets them to swim together.
But instead of being praised, he has been criticised by more than 50 animal rights groups.
Liu Huili, of Da'erwen campaign group, said: "Goldfish are small creatures that anyone can easily buy and abuse, or even kill."
She wants TV stations to drop the act from variety shows planned to mark the end of the Lunar New Year.
Some stations, including the state broadcaster CCTV, are reported to have agreed to ditch the controversial segment. Others plan to show it regardless.
Meanwhile, Mr Fu has hit back at the criticism.
"If I used magnets, the fish would stick together," he told a CCTV news programme.
"Some people say I use electricity or high technology. They can say what they want, but the fish are safe," he added.
The magician has declined to say exactly how the trick is performed.