Animal activists in China say a now-famous magic trick with goldfish swimming in sync for the Lunar New Year may have involved abuse including implanted magnets, and are asking the state broadcaster not to air it again.

Hundreds of millions of people watched the magic trick during a China Central Television gala on the Jan. 30 eve of the Lunar New Year festival. The gala is China's most watched broadcast of the year.

Goldfish are a symbol of wealth in China, but the image of six of them swimming in perfect sync under magician Fu Yandong's direction alarmed some Chinese, who worried that magnets were implanted in the fish or that they were controlled by electric current.

Fifty-three animal rights groups and other groups have sent a letter to CCTV asking not to let Fu perform the trick again during Thursday's broadcast of the Lantern Festival, which ends the Lunar New Year events.

"We should stand for nonviolence, harmony and tolerance, but to my great surprise CCTV, the state broadcaster, tells the public we can use animals for entertainment. I think this is just wrong," said Qing Shaona, director of the Capital Animal Welfare Association.

Fu won't explain how his trick works, but has defended his actions, saying on his Twitter-like microblog that the goldfish are "living happily."

Like many Chinese, the animal rights groups want to know how the trick is done and have asked for a group of independent experts to examine the fish. The letter warns against the "potential torture or injury to animals resulting from audience members trying to imitate performances."

China has been working on a draft animal protection law, but it's unclear when it will be passed.

It was not clear whether the magic trick was to be performed again Thursday, as the animal advocates feared.

The Beijing Times on Tuesday quoted Chen Linchun, the director of the CCTV Lantern Festival show, as saying plans for broadcasting the show again were only a rumor.

But Fu's agent, Liang Ming, said Wednesday that a repeat of the trick has been planned, though a final decision has not been made on whether it will be included in the Lantern Festival broadcast.

"It's not convenient for me to say anything now. Just wait and see," he said in a phone interview.

Liang has said Fu will continue to perform the goldfish trick. He denied that the fish are abused but said he agrees with the animal rights groups' concerns that the public might harm fish while trying to copy the trick.

The agent refused to explain how it's done, though. "It's absolutely not possible to make it known to the public how it works, because this isn't just one person's trick, it's a whole profession's."

CCTV referred any questions Wednesday to its office that handles the Spring Festival and Lantern Festival broadcasts, where the telephone remained busy.