Do You Actually Need a Quarantine Tank?

While quarantine tanks aren’t required, they are certainly are great to have around for when you get new fish or if you are dealing with a sick fish.

In this article, we’ll explore the question of “what is a quarantine tank”, how to set one up, and what the common uses of quarantine tanks are.

What is a Quarantine Tank?

Quarantine tanks are smaller gallon aquariums (5-20 gallons) with minimal filtration and lighting and typically no gravel. They are used for separating fish from a main aquarium whenever that is required. The two most common reasons for separating a fish are when they are new and just from the pet store and when they show signs of sickness or disease.

Quarantine tanks are an inexpensive insurance that can help to protect your community.

Setting Up a Quarantine Tank

Quarantine tanks are most often kept empty of water and stuffed in the back of a closet somewhere. When they are needed, they require minimal setup as long as you are adequately prepared.
Move your quarantine tank to where it will be set up. Make sure its within reach of outlets.
Fill your tank with TREATED water. All the water your tank gets should be dechlorinated. Your fish will likely need to end up in this tank as soon as possible, so water will not have time to dechlorinate on its own. Additionally, you’ll be using a sponge to jumpstart biological filtration and chlorine will quickly kill off all the beneficial bacteria.
Before you need your quarantine tank, you should put a sponge in the filter. This sponge will do nothing 99% of the time except serve as a location for beneficial bacteria to live. When you need to set up your quarantine tank, get the filter running and move the sponge into the tank at the same time the fish is added. This will help to provide somewhat of a nitrogen cycle, even it it can’t quite keep up fully.


The filter should be sufficient for the tank size. You don’t need anything fancy here. Just enough to get the job done.


As with the filter, you just need a heater powerful enough to get the job done.


It’s usually best to skip the substrate in a quarantine tank for several different reasons.

First, they are typically used as a temporary, “as needed”, tank that can be set up and taken down quickly. Gravel or sand just slow down that process.

Second, the substrate is a good medium for bacteria and parasites to live. You are trying to avoid that here.

Third, since you’re likely dealing with an uncycled tank, you want to be able to remove as much fish waste as possible. With the bare bottom, you’ll be able to see it all so it’ll be easier to clean.


Skip the lighting. Fish are more relaxed when its dim which can help in recovery. Some lights can also break down medications.

Decorations/Hiding Places

Many fish like to have some place to hide. This is especially true if they are sick, wounded, or stress – the exact reason you would put a fish in a quarantine tank. Keep it small and simple.

New Fish

When you buy new fish, they often come from atrocious conditions in the pet store. Putting them into a quarantine tank gives them the opportunity to recover from poor water parameters and extreme overstocking. This also gives you the opportunity to observe them and make sure they are healthy before adding to your tank rather than risk infection and potential disaster.
Many hobbyists do a 3 week quarantine on all new fish. This give adequate time for most diseases to fully show themselves.

By not quarantining your new fish, you risk introducing diseases into your healthy tank.

Sick Fish

Djpalme [Public domain]
Djpalme [Public domain]
If you have a fish showing signs of disease, it’s best to remove them from your main aquarium rather than risk infection in all of your fish. Quarantine tanks offer a place for your fish to recover without being bullied or nipped at as well as a location for you to treat your fish with medication.
It’s important to note that if you are using medication in a tank with a filter, you’ll need to remove any activated carbon as carbon will neutralize most medications.

Disassembling a Quarantine Tank

Once your fish is back in your main tank, it’s time to take the tank apart and store it for next time. It’s important to disinfect EVERYTHING.

Disinfecting a Quarantine Tank

Make a bleach and water mix with 2%-4% bleach and the rest water. Wipe down all surfaces using your bleach solution to kill any leftover diseases, unwanted bacteria, etc.

Once you’ve wiped everything down, thoroughly rinse everything off. It’s critical you get all of the bleach cleaned off to prevent issues next time.

Finally, once it’s been wiped down and all the bleach is off, dry the tank. Wipe it down with clothes and then let it air dry until its completely dry. A tank that’s stored wet will develop mold.

How Long Should I Quarantine My Fish for?

If you’re quarantining new fish, then 3 weeks is recommended.

If you’re quarantining a sick fish, then it will depend on recovery. Typically, 2 weeks after the last sign of symptoms. Remember that a sick fish not only needs to recover, but it needs not to be contagious.

How Often Do I Need To Do Water Changes?

In short, as often as you need to. You have taken a stressed fish and put it into an uncycled tank.

First of all, your sick or stressed fish needs water parameters as perfect as possible to help with recovering.

Second, you are dealing with an uncycled tank. This means that ammonia isn’t going to be converted into less toxic nitrates. So YOU need to help remove ammonia.

This often means daily water changes or every other day water changes. Keep in mind that you’re often dealing with smaller tanks, so they should be fairly simple and won’t take much time.

Do I Need To Acclimate My Fish To A Quarantine Tank?

Yes! Fish should be acclimated to a quarantine tank just like they would be when they are put in any new tank.

If it’s a sick fish, you can use some of the water from your main tank to help ease the transition. But even with some of the water being the same, you’ll still likely have to add new water which wont match temperature, etc.

If its a new fish, then the water is obviously different and you should acclimate them just as you normally would.