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

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 ...

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.

WWF works to sustain the natural world for the benefit of people and wildlife, collaborating with partners from local to global levels in nearly 100 countries.

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 ...