Just as the name sounds, a quarantine tank is a separate fish tank that is used to temporarily house aquarium inhabitants. For the most part, it contains all the main components of a fish tank. However, these quarantine tanks are rather minimal in set-up because these tanks need to be easily accessible and require daily water changes when in use.
 

There are two main reasons for why someone might want to use a quarantine tank. The first reason is to isolate new fish before they are introduced into the main aquarium. This helps ensure that the new livestock won’t infect your main fish tank with any pathogens they might have. Following the same vein, a sick fish from the main tank might need to be taken out of the aquarium and housed separately to prevent the spread of a potential outbreak.

When setting up your quarantine tank it’s important to know that your tank doesn’t need to be a fancy display tank with everything perfect down to the last detail. All you really need is a bare bones setup with the following equipment.

Like all fish tanks, some type of filtration is needed. Whether it be a hang on the back filter or a simple sponge filter. It doesn't matter too much. Just make sure that there is no chemical filtration that will remove the medication that you are adding.

You want your tank to stay at a stable temperature. I would suggest that the tank temperature should be at what the fish you are quarantining prefers. If needed, some fish illnesses require higher temps to allow for faster recovery. If this is the case I would recommend adding an airstone to help increase dissolved oxygen in the water. At higher temps water holds less oxygen.

I would recommend you have a general puprose testing kit that tests for Ph, Ammonia, Nitrites, and Nitrates.

It would be a good idea to always have medicine on hand. Typically you want a general puorse medicine that can treat for parasitic, fungal and bacterial pathogens. I wouldn’t recommend specific medicines until you know what you're up against.

Make sure any fish equipment you use in this tank is separate from your other main tanks. You don’t want to cross contaminate your main tank with infected nets or water changing equipment.

For newly acquired fish you will want to acclimate them to the water in the quarantine tank and monitor them very closely for a period of two to three weeks. Monitor the water parameters with your test kits and check for signs of parasites or bacterial infections. If the newly acquired fish do come down with something you will need to use the appropriate medication and you will need to keep them in quarantine for a longer duration. If after a few weeks no problems develop, you can then acclimate them to the main tank.

If a fish comes down with something while in your main tank, just net them and plop them into the quarantine tank. There should be no need to acclimate them because you used water from your main tank. If you didn’t use water from the main tank you will need to acclimate them to the quarantine tank water. Diagnose the problem/disease and treat appropriately. After the disease clears up you will still want to keep the fish in quarantine for a week or so monitoring the water parameters with your test kits the whole time.