They grow bigger than you think.

Authorities in Minnesota have appealed to aquarium owners to stop releasing pet fish into waterways, after several huge goldfish were pulled from a local lake.

 Officials in Burnsville, about 15 miles south of Minneapolis, said released goldfish can grow to several times their normal size and wreak havoc on indigenous species.

 “Please don’t release your pet goldfish into ponds and lakes!” the city tweeted on Friday. 

“They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants.” 

 Last November, officials in nearby Carver county removed as many as 50,000 goldfish from local waters. The county water management manager, Paul Moline, said goldfish “are an understudied species” with “a high potential to negatively impact the water quality of lakes”.

 Like carp, goldfish can easily reproduce and survive through low levels of oxygen during the Minnesota winter.

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