Both new and experienced pet fish owners often fret about finding a healthy species to introduce to their aquarium. But, how do you even measure the health of one species against the others?

Deep below the surface of a river in northern Brazil, a “shy” creature tucked its “armored” body into a rocky crevice. Divers ...

This species, with its many varieties, is the most common betta fish found in aquariums and pet stores, but it has more than 70 relatives, including the endangered Betta miniopinna and Betta ...

Koi have six types of color cells in their skin ... Koi are actually a type of carp, and today they're some of the most expensive pet fish in the world. But why? Koi were originally raised ...