A small lake in Boulder, Colo. has been overtaken by thousands of invasive goldfish.

The state agency responsible for managing Colorado’s state parks and wildlife believes it all started when a few “unwanted pet fish” were dumped into the lake and then multiplied into the thousands.

“These are domestic fish actually,” Colorado Parks and Wildlife spokewoman Jennifer Churchill told USA Today “These are fish from a store, I imagine. They can out-compete the native fish.”

According to the state wildlife agency, the goldfish pose a threat to the natural ecosystem of the lake.

“Dumping your pets into a lake could bring diseases to native animals and plants as well as out-compete them for resources,” Churchill told ABC.  “Everything can be affected. Non-native species can potentially wipe out the fishery as we’ve put it together.”

To avoid wiping out the lake’s native fish — including blue gills, channel catfish and sun fish — the agency is considering two options to remove the goldfish: draining the lake or electroshock.

“With electroshocking, you go in the boat and stun the fish to paralyze and collect them,” Churchill told ABC. Shocking fish does not kill them, she explained. “The fish could also be collected if the lake is drained,” Churchill added.