Giant Goldfish Causing Havoc in Lakes After Being Released by Pet Owners

Officials in Minnesota have warned people not to dispose of unwanted goldfish in lakes or ponds while also sharing images of some which have grown to enormous sizes.

The City of Burnsville, located just south of Minneapolis, posted photos online of huge goldfish which were found in Keller Lake, while warning of the dangers to the environment caused by releasing such fishes into local waters.

"Please don't release your pet goldfish into ponds and lakes! They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants," the City of Burnsville account tweeted on July 9.

The post has since been retweeted more than 5,200 times.

In a further post on Facebook, the City explained that it had recently partnered with neighboring Apple Valley and Carp Solution to conduct a survey on Keller Lake to assess populations of "invasive goldfish" and other fishes.

The City noted that there have been large numbers of goldfish reported in the lake in recent years as people decide to release them into the wild after getting them as pets.

Officials in Burnsville pleaded with people to find other ways of getting rid of their goldfish, noting that they can contribute to poor water quality of lakes at high populations.

Please don't release your pet goldfish into ponds and lakes! They grow bigger than you think and contribute to poor water quality by mucking up the bottom sediments and uprooting plants.
Groups of these large goldfish were recently found in Keller Lake.

— City of Burnsville (@BurnsvilleMN) July 9, 2021

"Instead of releasing your pet goldfish in a local lake or pond, please consider other options for finding them a new home, such as asking a responsible friend or neighbor to care for it," the City of Burnsville wrote on Facebook.

While small and harmless when sold as pets, goldfish cause major problems when they are freed in fresh water such as lakes and ponds.

The Minnesota Department of Natural Resources (DNR) lists goldfish as a regulated invasive species, which while legal to own, sell and transport, must not be not be introduced into a "free-living state" such as being public waters.

Earlier this year, the DNR used goldfish as an example of what can occur when people wrongly place fishes in public waters.

Because they're part of the minnow family, goldfish can work their way through city stormwater ponds and into lakes and streams downstream. The fact they can reproduce rapidly, increasing the amount of plants being uprooted and bottoms of lakes being disturbed, means drastic action is needed to remove them from water supplies.

The DNR said that a few years ago, all the fish in a pond at Eagan's Central Park had to be killed in order to control the goldfish population after one was discarded into it.

"We tried netting them out and we got thousands of them, but we couldn't get them all," City of Eagan water resources specialist Jessie Koehle said. "Eventually we had to use rotenone to reclaim the pond, killing all the fish and starting over."

The DNR noted that "the whole episode could have been avoided" if the goldfish owner had properly disposed of the fish.

"Goldfish have the ability to drastically change water quality, which can have a cascade of impacts on plants and other animals," Caleb Ashling, Burnsville's natural resources specialist, told The Washington Post. "They are a major concern.

"People are trying to be nice, but they don't realize that goldfish can really have a lot of unintended consequences," Ashling added. "Most people really care about their lakes and ponds, but you may be causing problems you weren't aware of if you let them go there."

giant goldfish
The City of Burnsville shared images of the massive goldfish found in Keller Lake while urging people to dispose of their pets properly. City of Burnsville