Goldfish possess genetic traits that allow them to swell up to four pounds—the size of a Chihuahua. Experts say that's why ...

They are now the most commonly kept freshwater fish species across the globe. One of the biggest misconceptions about goldfish is that they can thrive in small bowls. However, this is not true.

You see, goldfish waste contains toxins like ammonia that can burn gills and even damage the brain. In the wild, this isn't a problem. Freshwater lakes and ponds are home to armies of bacteria ...

Something fishy is going on. A pet store goldfish went from “cute to brute” after it was found in a Pennsylvania waterway – with experts now warning against dumping unwanted fish into ponds ...

This story appears in the April 2017 issue of National Geographic magazine. Hundreds of millions of people worldwide would lack their prime source of protein without freshwater fish. Yet the lakes ...