Freshwater lakes and ponds are ... You have to introduce it, and that's where a lot of goldfish owners slip up because you can't just buy a fish the same day you get your tank.

This genetic condition is more common in freshwater aquarium fish species, such as goldfish. Fish with polycystic kidney ...

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 ...

Scientists have decoded the secrets behind a goldfish's ability to survive in ice-covered lakes. They've worked out how and why the fish turn lactic acid in their bodies into alcohol, as a means ...

A report has warned of a "catastrophic" decline in freshwater fish, with nearly a third threatened by extinction. Conservation groups said 80 species were known to have gone extinct, 16 in the ...