A city in the US state of Minnesota has urged residents not to release their unwanted pet fish into the wild after finding huge goldfish in a lake. The common household pets can grow far bigger in the wild and cause major disruption to ecosystems. The city of Burnsville shared images showing several monster goldfish caught during a survey of Keller Lake. It said goldfish could contribute to poor water quality by disturbing sediment and uprooting plants. “Please don’t release your pet goldfish into ponds and lakes!” the city wrote in a tweet. In Minnesota, goldfish are a regulated invasive species, which means it is illegal to release them into public waters.