Aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life.It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin.
Aquatic animals belongs to freshwater or saltwater. However, the adjective marine is most commonly used for animals that live in saltwater, i.e. in oceans, seas, etc.
FRESHWATER AQUARIUM FISH
They mainly belongs to following catagories kept in Aquarium
Bichirs and reedfish
Characins and other characiformes
Cyprinids Killifish Labyrinth fish
Loaches and related cypriniforms
Neotropical Electric Fish