A quarantine tank, often abbreviated to "q-tank", is a tank used for temporarily housing new fish or coral before adding them to an established aquarium. The quarantine tank allows the aquarist to observe the new fish or coral for signs of disease or parasites and, if necessary, treat them before adding them to the main tank. Despite the benefits of using a quarantine tank, many aquarists do not have one. One reason for this may be that some aquarists believe that a quarantine tank is not necessary if they are careful about only buying healthy fish and coral. However, even healthy fish and coral can carry diseases or parasites that can infect an established aquarium. Another reason some aquarists do not use a quarantine tank is that setting up and maintaining a quarantine tank can be time-consuming and expensive.