Lake Tahoe and its native residents have been under attack from exotic species possibly since the most threatening of all arrived on its shores.
That species is modern man and its likely we've been responsible one way or the other for the rest.
Those who worry about the lake and its clarity spend a good deal of time and effort monitoring and managing aliens like the Asian clam and the large mouth bass and keeping even more damaging immigrants, like the quagga mussel, out.
"We don't have a bar around the lake," says researcher Christine Ngai of the University of Nevada Reno, "so things can come in however many ways that you can imagine.:
A few years ago Ngai and other researchers heard sightings of new arrivals.
"We've actually been told by residents and fishing guides that they've seen a really large goldfish."
Which sounded a little unlikely.
"When someone tells you they've seen goldfish the size of your head or bigger you don't usually believe that."
The reports were accurate. Goldfish, probably discarded pets, are surviving and growing to impressive size in the warmer waters near Tahoe Keys. The largest caught so far was a four pound female.
She was ripe with eggs, but so far no goldfish fry have been spotted and though they continue to show up, there's no indication their numbers are growing.
What threat they may pose is uncertain, but there are worries they will compete with or eat native minnows which are already declining and then there's that by-product familiar to anyone who's kept a goldfish bowl.
They eat and poop a lot. That poop means more nutrients in the water.
And that, Ngai says, would add another threat to the clarity that is the lake's signature feature and environmentalists' and residents' biggest concern.
Researchers will keep an eye on these monsters from now on, but they caution anyone who thinks they're being kind by freeing Mr. Bubbles in the great outdoors to think otherwise.