Aquarium fish are any type of fish that can exist outside of the great wide open of the natural environment and instead thrive normally in an aquarium. An aquarium is any enclosed container of water that allows for the sustenance of fish, plants, and other wildlife inside the enclosure. These aquariums can only work if there is enough oxygen in the water in the container. Otherwise the fish and other organisms will just die. Thus, make sure you are using a proper circulation system that constantly pumps new water into the tank. Ask an aquarium expert or someone at a pet shop supply store what kind of oxygenation system you should be using.
Some of the most popular types of fish to be included in aquariums are tetra neon, tiger barb, zebra fish, guppy fish, goldfish, and angelfish. These fish are popular because of their external beauty – they way their scales flash as they flit and twist and otherwise do their fish ballet. They are like a piece of living, breathing (through gills) abstract art. These types of fish are also popular because they are known to be well accustomed to the smaller environs of an aquarium. Another type of fish is also suited to aquariums.
Sharks! There exist many different species of shark that are small enough to live their lives in an aquarium. Sharks can be quite formidable when placed with other fish, since they are natural predators, so be sure to choose carefully. If you want both sharks and non-sharks, you should probably place them in separate containers, but ask the experts about specifics.