A saltwater aquarium, also known as an oceanarium, is an aquarium specifically for fish, mammals and plants that live and grow in the ocean [source: Britannica]. As its name implies, a saltwater aquarium contains saltwater, which is maintained within a specific temperature range [source: Sea World]. Here's how to set up a saltwater aquarium:

  1. Prepare the tank Install the filter system in your aquarium. Fill your aquarium with clean, fresh water, and add salt purchased at a pet supply store. Follow the instructions regarding the ratio of salt to water. If you're using tap water, remove the chlorine by adding a dechlorinator. Turn the water heater on and set the temperature. Run the system for a few days to make sure everything is working fine.
  2. Put in the foundation Create a foundation by putting 2 to 3 inches (5 to 7.6 centimeters) of live sand containing bacteria and micro-organisms on the floor of the aquarium. Place live rock, which comes from ocean reefs, on top of the sand. These rocks also contain necessary bacteria and provide natural hiding places for the fish. There are many different sizes, colors and shapes to choose from.
  3. Install the lighting Install the aquarium lighting system. Attach it to a timer and set it to be on for 10 to 12 hours each day. This will cause algae to grow. When you see algae growing, add algae-eating fish and invertebrates to the aquarium.
  4. Introduce the fish Place small, non-aggressive fish in the tank and let them acclimate to their new environment. After a few weeks you can begin adding larger, more aggressive fish and invertebrates. Limit the amount of fish in the aquarium to no more than ½ inch (1 centimeter) of fish for every gallon (3.8 liters) of water in the aquarium. This will help ensure that the fish thrive [source: Pet education].