Saltwater Quarantine Tank Setup – Your Questions Answered

In this article, I will answer some of the most common questions about saltwater quarantine tanks.

Saltwater quarantine tanks are a necessity that many hobbyists forget to consider. Not everyone uses a quarantine tank but I highly recommend that you do.

While offering great use these tanks come with many additional benefits. They should be used for all fish before they are introduced to a new aquarium.

Giving them a comfortable, easy to adjust, and safe place before they are added to the main tank is the key to success.

There is always a chance of a fish having a disease or parasite which will get into your main tank without you knowing.

A properly set up quarantine tank will prevent this from happening. 

Additionally, they can be used as a hospital tank to help treat sick fish and to cut off unwanted parasites completely.

Keep in mind that aquatic life easily stresses during transportation and relocation, which is why they need space to reduce stress and get comfortable in a new environment.

Making the saltwater quarantine tank the perfect resting ground before they head over to their new home.


Common questions about saltwater quarantine tanks 

What is a quarantine tank?

These are separate tanks that are used to isolate and observe new fish before adding them to your main tank.

They can also be used as a hospital tank to heal sick fish and help new fish learn to eat certain foods without the harassment of other fish. 

saltwater quarantine tanks

Who needs a saltwater quarantine tank?

All aquarists should have a saltwater quarantine tank, but usually, skip out on it due to maintenance and expenses. However, they run the risk of spreading diseases, infecting other livestock and even causing the death of their beloved aquatic life.

The common misconception about quarantine tanks is that they need to be expensive and large, which is not true in any way. Once you have an affordable system set up, you will be able to reap the rewards for years to come. Additionally, it’s many other uses will ensure you are happy keeping a quarantine tank readily available.


What are the benefits of a quarantine tank?

Using a saltwater quarantine tank can help you reduce infectious diseases, and cut off their impact of other fish and livestock around them to 0%. Think of it as an extra aquarium that will come in handy for different uses.

By keeping up with a quarantine tank, you will be able to help set up your new fish easily. Acclimating and getting used to a new space while offering them a specific diet and a stress-free environment will be of great benefit. This will also allow them to gather themselves and get familiar with the space.

Additionally, when looking to medicate your fish you need a reliable system that does not suck up the medication. By using a quarantine tank you are able to ensure that just the fishes that require treatment have access to it. You won’t want to medicate your whole tank when not necessary.

Moreover, a saltwater quarantine tank can help you breed fish, and can even be used for a recovery process, or be dedicated to “grow out” space. Grow out tanks are very helpful for smaller fish that might be bullied and stressed by other tankmates.

fish diseases

Does a quarantine tank need to be cycled?

It is not necessary for a quarantine tank to stay running once you are done using it. Most people will set up the tank when it’s needed and then shut it down.

The filter media being used should be cycled when you set up the tank. So the tank does not need to stay running and cycled but when it is first set up, you will need it to be cycled prior to adding fish. Using cycled media, filter sponge, live rock, bacteria, can all help to start a new tank.

Any rock in the tank should be removed before adding medications. 


How to keep a quarantine tank cycled?

If you don’t shut down your quarantine tank and want to keep it running, the easy way is to keep some cycled bio-media available to use at any time.

This can be a sponge or cycled media. Keeping some inside the sump of your main tank is easy to take out and add to the quarantine tank.

You can also add ammonia periodically over time to keep the cycle or add some small inverts and feed them to keep the tank cycled. 


How big should a quarantine tank be?

You don’t need a large tank for a quarantine system. A 30-gallon tank is normally large enough for most fish, but if you are planning to buy larger fish, then you should use a larger tank. 


How long to quarantine saltwater fish?

Any new fish that you purchase should be placed into a quarantine tank for a period of time. 

It is recommended to keep fish in quarantine for 2 to 4 weeks. Most people will treat the tank with copper-based medications for a period of 14-21 days.

If you are treating for bacterial infections you must ensure it’s obvious symptoms. These range from red spots, ragged fins, and others.

While working on healing your fish we suggest you change 10% to 15% of the water every other day, or as necessary, as it can help maintain the health of the quarantine tank.


How do you set up a quarantine tank?

When it comes to setting up a new saltwater quarantine tank there are a number of ways you can go about the process. Setting up a quarantine tank is not difficult and should be kept simple.

You don’t need a lot of expensive equipment. As every saltwater quarantine tank is unique in nature, the best way to get started is with a bare 20 or 30-gallon tank. It offers a comfortable space and is easy to maintain.

For equipment, you only need a basic hang on filter or sponge filter, heater, wavemaker or powerhead (if needed), and something for the fish to swim in and around.

You can use some PVC plumbing and a basic decoration in the tank. You don’t need to use sand or live rocks as they can actually absorb medications. Bare bottom tanks are easy to keep clean.

Although a light is not necessary, one should be used to provide a natural light source for the fish. A basic LED will be sufficient. It does not need to be suitable for corals as there are none kept in the tank.

As mentioned, keep the quarantine tank setup simple. It’s best to not use substrate and go with a bare bottom tank as you want to maintain pristine water conditions. Keep in mind that the rocks substrate, and the filter media system will make it harder to ensure a set medication level. So I choose to go without it.

A basic square or cube tank will work fine providing it is in decent condition and hold water fine. No need for high-end showpieces here. Unless of course, you want that.


What do you do with a quarantine tank when not set up?

If you don’t want to keep the tank set up and running, which will need to stay cycled, it’s best to shut it down and keep it for another time.

I will empty and clean out my quarantine tank, put it away until I need it again. It is easy to keep a cycled sponge in your sump tank to be used anytime you need it.

You will also save energy by shutting down the tank. 


Is a quarantine tank necessary?

Although a quarantine tank is not necessary, it is highly recommended. By setting up a simple quarantine system, you can avoid a disaster by adding a sick fish to your main tank which can be a costly mistake. 

What is the difference between a hospital tank and a quarantine tank?

Hospital tanks and quarantine tanks are basically the same things as they are used to isolate and observe fish. But they do provide a different purpose. Quarantine tanks are used for new fish to isolate and observe prior to entering your main tank. If they have a disease, they can be treated.

A hospital tank is used for fish that have already been in your main tank for a period of time and need to be removed and treated for an illness. You may end up using different treatments depending on the illness where in a quarantine tank, you may not use any medications if the fish is healthy.


Marine Depot Aquarium Supplies

Should you use sand in a quarantine tank?

You can use sand in a quarantine tank but I choose not to. If I need to treat a fish for disease or other illnesses, the sand can actually absorb medications.

Also, some medications can kill bacteria within the sand causing an ammonia spike which can be very harmful to the fish in quarantine.

If no medications are being used, then sand is ok to use.


Should you use a filter in a quarantine tank?

Yes, you should use some sort of filter on your quarantine tank. A common filter to use is a hang on the back style. These filters are easy to access and maintain, they are affordable and provide space for cycled filter sponge or media. You can also choose to use a sponge filter with an air pump or canister filter. 

I recommend the Seachem Tidal filter. Check out today’s price on Marine Depot.


Can you use an ATO on a quarantine tank?

Yes, you can use an auto top off system on a quarantine tank. Although it is not needed, it can be beneficial and convenient. An auto top off system will help maintain accurate salinity levels in any saltwater tank.

The Tunze nano auto top off is perfect for quarantine tanks. Check them out on Amazon here.

Does a quarantine tank need a light?

No, a quarantine tank does not need a light but it is recommended. Ambient light is fine but you want to avoid direct light as it can aid algae growth. A basic LED light will provide a natural light cycle in the tank to benefit the health of the fish and enhance natural activity. 

If you want a basic LED light that is affordable and works great, check out this light on Amazon.



Keeping a quarantine tank is important for new fish to be isolated and observed before being introduced to the main tank. The key to a successful quarantine tank is to keep things easy and simple. Provide your new or sick fish with a healthy environment with hiding places and good water conditions and you will find that treating a fish with medications or introducing a new fish, your chances of success are greatly improved!

Hopefully, these questions and answers are helpful in guiding you towards using a quarantine tank for your new fish.