They're easy to take care of, inexpensive and entertaining, but tropical fish and other aquatic pets including exotic fish, turtles, bass and carp are getting into local waterways and breeding and competing with native species.

In Coquitlam, so many exotic fish are winding up in Como Lake that the city is cracking down with hefty fines ranging from $2,500 to $250,000.

The fish, which look like goldfish, appear to actually be a species of fathead minnows, which are commonly sold by pet stores as feeder fish for other species.

David Scott, from Simon Fraser University's School of Resource and Environmental Management, said there's good cause for concern.

Como Lake goldfish

Dozens of tropical fish dot the surface of the water in Como Lake while many more swim below. (CBC)

"If you have non-native species that become established in let's say the Fraser River, they would be competing and influencing dozens of local species that we have here including salmon which are economically important," he said.

In 2012, the infamous snakehead fish eluded conservation officers for weeks. Scott was one of the SFU researchers who studied it.

People may think they're freeing a captive pet by throwing it into a local pond, he said. But the act can have bigger implications than most people realize, Scott warned.

So what do you do, if you don't want your pet fish or turtle anymore?  Many pet stores say they'll take them back.

With files from the CBC's Farah Merali