A quarantine tank is a tank that is used to quarantine new fish or other organisms that are later intended to be introduced into another, primary aquarium. Quarantine tanks can also serve as "hospital tanks", where sick or injured fish are taken from the main aquarium and given treatment. Quarantining a fish can help stop the spread of a contagious disease, such as Ichthyophthirius multifiliis.
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Quarantine tank Wikipedia(Text) CC BY-SA