'''Fish''' are aquatic cold-blooded [[vertebrates]] with fins and scales. Many species of fish are often kept as pets in containers known as [[aquarium]]s. Fish are generally divided into two groups: [[freshwater]]-dwelling and [[saltwater]]-dwelling, and fish from one group are generally unable to survive in the environment of the other. There are, however, a small number of [[species]] that move between saltwater and freshwater at different stages of their lives. | '''Fish''' are aquatic cold-blooded [[vertebrates]] with fins and scales. Many species of fish are often kept as pets in containers known as [[aquarium]]s. Fish are generally divided into two groups: [[freshwater]]-dwelling and [[saltwater]]-dwelling, and fish from one group are generally unable to survive in the environment of the other. There are, however, a small number of [[species]] that move between saltwater and freshwater at different stages of their lives. |