How to Introduce a New Fish to an Aquarium

Introducing a new fish to an established aquarium can be stressful to the fish. Most people will put the fish into the tank immediately, causing the fish trauma or shock, which could be fatal. However, a fish can easily be moved into a new tank and stay healthy. The aquarium owner must take a few preliminary steps before introducing the fish, and continue to carefully observe the fish's behavior.

Things You'll Need

  • Water testing kit
  • Fish net
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Instructions

    • 1

      Measure the water's pH and hardness to make sure the fish you are introducing can handle the chemistry levels of the tank. The tank must be cycled and have a good colony of beneficial bacteria before introducing the fish.

    • 2

      Buy a live fish from a respectable pet store or breeder. A healthy fish will have no difficulty swimming or breathing, and will show no signs of injury or infection. The store will place the fish in a plastic bag filled with oxygen so the fish can breathe while it is being transported.

    • 3

      Float the plastic bag containing the fish in the aquarium water for about an hour to equalize the temperature in the bag with the temperature of the tank. This prevents any stress that could be caused by sudden change of temperature.

    • 4

      Cut open the bag, and with the net, scoop the fish from underneath when it swims toward the surface.

    • 5

      Submerge the net in the aquarium water and let the fish swim out--do not just drop the fish in. The pet store water may contain diseases, so do not let any of the bag water get into the aquarium water.

    • 6

      Watch the new fish carefully for signs of illness, shock or aggression. To minimize shock, keep the tank lights off and provide places for the new fish to hide.