Let this 14-inch goldfish caught in the Niagara River be your answer.

It sounds like the most outrageous of urban myths: When you flush a goldfish down the toilet it survives and becomes an enormous super fish in the wild. But this is no myth! And in fact, it's a huge problem. The goldfish are taking over.

Exhibit A: The photo above. Recently posted on Facebook by Buffalo Niagara Waterkeeper (BNW), this whopping 14-inch goldfish was found in the Niagara River. BNW writes,

This is why you should never flush your fish! This 14-inch goldfish was caught in the Niagara River, just downstream of the wastewater treatment plant. Goldfish can survive year-round in our watershed and can destroy the habitat of native fish. Scientists estimate that tens of millions of Goldfish now live in the Great Lakes. If you cannot keep your pet, please return it to the store instead of flushing or releasing it.

As Smithsonian reports, goldfish – which are domesticated carp originally bred in ancient China but introduced into the United States during the mid-1800s – are an ecological nightmare:

In addition to disturbing sediment and vegetation found at the bottom of lakes and rivers, the invasive fish release nutrients capable of triggering excess algal growth; transmit exotic diseases and parasites; feast on a diverse diet of fish eggs, small invertebrates and algae; and reproduce at higher rates than most freshwater fish.

In addition to the millions of goldfish living in the Great Lakes, the vibrant runaway pets are making themselves at home in such far-flung places as London’s Epping Forest, the Canadian province of Alberta, Nevada’s Lake Tahoe Basin and Australia’s Vasse River.

While nobody knows for sure how the strapping goldfish above ended up in the Niagara River – whether it was flushed or released by a pet owner directly into the water – the story may have ended well for the fish, but not so much for the water. "Aquatic invasive species that don't naturally belong in the Great Lakes, like this goldfish, are a constant threat to the health of native wildlife populations and their habitats. Large and small, hundreds of different invasive species continue to disrupt and cause damage to our Great Lakes," writes BNW.

We covered this more in-depth a few years ago but couldn't pass up on the opportunity to dive into it again. Not only is it a good reminder to be careful with you invasive species ... but also to watch what you flush down your toilet.

To that end, BNW has some good advice on responsible flushing. Remember, in the same way that throwing something in the trash doesn't mean that it then just magically disappears, neither does flushing something down the toilet – in some cases, flushing things can send them directly into waterways.

The organization explains that older "combined" systems collect rainwater and snowmelt, as well as household wastewater waste, which usually stop by treatment plants on its way out. But when there is heavy rain or snowmelt, the "pipes that carry the wastewater are overwhelmed, and to safeguard homes, businesses and the treatment plant, the sewer overflow will be released into local waterways with little to no treatment."

The best rule of thumb is to flush only two things down the toilet: Toilet paper and things that come from your body, to put it delicately. That means no household chemicals, feminine products, wipes, cat litter, medications, et cetera. Even products that promise they are flushable should not be flushed.

And especially, don't flush your fish! I am not sure if people flush fish because they think it's the fish's ticket to freedom or if it's supposed to be some kind of euthanasia – but it's just a bad idea. Since the thought of a life in a fishbowl seems pretty depressing, maybe skip buying a goldfish in the first place? But if you end up with a fish that you can no longer keep, consider returning it to a pet store, donating it to a school, or putting it up for adoption. The world's freshwater is having enough problems without giant gangs of goldfish gone wild taking over aquatic ecosystems.