Quarantine Tank

Proper quarantine of new fish and even invertebrates is so incredibly important to your long-term success as an aquarist. You can’t always see parasites and pathogens with the naked eye and if they get into your display tank via a new fish or coral, they can infect the entire tank. In the worst-case scenario, you could have a complete wipeout, losing all your precious collection to disease.

A quarantine tank provides a safe haven for new fish to be isolated and observed. Should a disease or parasite come up, the fish can then be medicated and treated in that QT tank.  Even if an existing fish starts to look sick in the main display tank or is attacked by a tank mate, it can be moved to the quarantine tank for treatment. 

This will not only drastically reduce the risk of introducing pests and disease into your display aquarium, but will also allow you to use more effective medications that would otherwise be unsafe for use in your display aquarium containing corals and invertebrates.  

Here's What You Need:

Tank size:

A quarantine tank doesn’t have to be large and a 20 gallon, 24” long tank is fine for most fish up to 4” long.  For larger fish, a 40 breeder or similar 36" long aquarium is best.  These are just general guidelines that work in most scenarios, if you are keeping much larger "show-size" fish or have an extensive collection, you probably will have more than one QT tank.  

Bare Bottom:

The bottom of the quarantine tank should be bare. Some parasites' life cycles involve a substrate dwelling stage, by not using sand you can reduce or eliminate the reproduction of some parasites.  This will also make it easier to keep the tank clean because leftover food and waste can quickly be siphoned out and won't get trapped up in the sand. 

Mature Filter:

Some kind of filtration is required and usually comes in the way of a power hang-on filter or internal filter of some kind. These are simple and effective filters that won't require a ton of maintenance which is the goal for your QT tank. Having some cycled bio-media for the filter or letting the sponge filter cycle first is going to help ensure the QT tank is stable and ready for the addition of new fish. Using a QT tank without cycled biological filter media means ammonia will be a threat and heavy water changes are to be expected.  

Air Pump:

Parasitic infections often cause breathing difficulties, and some medications can lower oxygen levels. Having an air-pump, tubing, and air stone on hand is not a bad idea just in case you need to oxygenate the water more effectively than what your filter can provide. 


A QT tank does not require any kind of special lighting but having a small light can be useful in observation.  A simple low-output freshwater LED light or similar light can help to observe the fish for signs of disease or parasites.


Always use a tight-fitting lid or screen top to keep fish inside the QT tank at all times. Fish in a QT can be exceptionally susceptible to stress. 


A heater is necessary to maintain stable water temperatures at all times. Be careful not to oversize your heater either, small tanks can overheat quickly.  

Tank background:

A solid color background can be useful in reducing environmental stress and help with observation in the tank. 

Shelter & Decor:

Fish need somewhere to hide and feel comfortable. Short lengths 2-4" diameter PVC pipe or similar PVC fittings work out great and won't absorb medications like you can experience with certain porous rocks and decor. 

Other equipment:

You’ll still need test kits for ammonia, nitrite, and nitrate to monitor that water quality in the quarantine tank. A refractometer and thermometer are also going to come in really handy but likely already something you have for your display tank. A copper test kit and various medications are also pretty common alongside a QT tank. 

Learn How To Properly Quarantine New Saltwater Fish with BRStv