Pet goldfish released in river grows to size of football

What do you do with an unwanted goldfish?

In Australia, many people are dumping their tanks in local rivers, freeing the fish and the former pets are growing, and growing and growing.

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Scientists are finding that the fish, which are part of the carp family, are swimming in rivers, traveling more than 142 miles in a year, the BBC reported.

Dr. Stephen Beatty said his team from Murdoch University has found many of the former house pets weighing more than a kilogram, or about two pounds.

But that's not the largest they have found. The biggest goldfish came in at 4 pounds.

They're tracking the fish movements and sizes to help learn to control the invasive species.

Experts say dumped goldfish can harm water quality, disturb habitats and compete with native species.

If left to grow and thrive, they can live up to 25 years and be more than 15 inches long, the RSPCA said.