Set Up A Quarantine Tank: For New and Sick Fish

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Quarantine tanks provide a safe and controlled environment for new fish to acclimate to their new surroundings, as well as a place to isolate sick or injured fish from the main tank.

In this article, we will explore the reasons why quarantine tanks are important and how to properly set one up.

Understanding Quarantine Tanks

A quarantine tank is more than just an isolated space; it’s a sanctuary where new fish can adjust and sick fish can heal.

When you add fish to your main display tank, you may unknowingly bring in diseases or parasites.

According to MSD Vet Manual “Preventing disease is always preferable to treating it. “

A quarantine tank or hospital tank acts as a buffer, allowing you to observe the new arrivals for any signs of illness before they join the main community.

Similarly, if a fish in your display tank falls ill, a separate aquarium provides a calm place for recovery, without risking the health of the other inhabitants.

It’s not a mere convenience; it’s a crucial part of maintaining a healthy and harmonious aquatic environment.

Why Use a Quarantine Tank

Using a quarantine tank is crucial for several reasons.

Firstly, it helps prevent the introduction of new diseases, parasites, and pathogens to the existing fish in the main tank.

New or sick fish are often carriers of diseases and parasites, and introducing them directly into the display tank can quickly spread the infection to the other fish.

Why Use a Quarantine Tank

By isolating new fish for a few weeks, we can observe them for any signs of disease or illness before introducing them to the aquarium.

Secondly, a quarantine tank provides a stress-free environment for sick or injured fish to recover.

When a fish is sick or injured, it can become stressed, which can weaken its immune system and make it more susceptible to diseases.

By isolating sick or injured fish in a quarantine tank, we can provide them with a peaceful environment to recover without the risk of being harassed by tank mates.

Thirdly, a quarantine tank allows us to treat sick fish without affecting other fish.

When a fish is sick, we need to treat it with medication to cure the disease.

However, some medications can harm invertebrates, snails, or certain species of scaleless fish.

By treating fish in a quarantine tank, we can avoid harming other fish in the established tank.

Lastly, a quarantine tank can also be used as a temporary home for fish that need to be removed from the aquarium due to aggression or injury.

It can also be used as a grow-out tank for newly hatched fry or as a breeding tank for fish.

Setting Up a Quarantine Tank

Setting up a quarantine tank is really easy to do.

Here are some steps to follow:

Choosing the Right Size

First, you need to choose the right tank size.

A 20-gallon tank is generally recommended for most fish, but the size may vary depending on the number and size of fish you plan to keep.

It’s important to have a lid or cover for the tank to prevent fish from jumping out and to keep curious pets from getting in.

Setting Up a Quarantine Tank


Next, you need to set up the tank with the appropriate equipment.

A heater is necessary to maintain stable water temperatures at all times.

Be careful not to oversize your heater either, as small tanks can overheat quickly.

A sponge filter or internal filter is also recommended for biological filtration.

I prefer not to put any substrate in the quarantine tank as it makes it so much easier to clean so a bare bottom tank is ideal.

Keep the tank running 24/7, so when needed, you can use it immediately.

You must also cycle the quarantine tank just like your main aquarium.

If you don’t know what cycling means, then please read this article for more details.

Adding Decor and Plants

Decor and plants are not necessary, but they can help reduce stress and provide hiding places for fish.

Plastic plants are a good option since they are easy to clean and won’t introduce any unwanted pests or diseases.

You can also add rocks, PVC pipes, or a flower pot for additional hiding places.

What is a quarantine tank

Avoid Cross Contamination

Avoiding cross-contamination between the display tank and the quarantine tank is needed or else the whole idea of using a quarantine tank is useless.

Utilizing separate equipment for each tank is not just a recommendation; it’s a necessity.

Tools like nets, siphons, or algae scrapers, if shared between the tanks, can easily transfer diseases or parasites from one environment to the other.

By dedicating specific tools to the quarantine tank and never using them in the main aquarium, you create a barrier that helps maintain the health and integrity of both environments.

It’s a simple yet vital practice that safeguards the well-being of your fish.

Remember, in the delicate ecosystem of an aquarium, even a small oversight can lead to significant problems.

Investing in separate equipment for your quarantine tank is a small price to pay for the peace of mind it brings.

Maintaining Water Quality

Maintaining water quality is a crucial aspect of keeping fish healthy.

Poor water quality can lead to stress, disease, and even death.

Here are some tips on how to maintain water quality in your quarantine tank:

  • Perform Regular Water Changes: Regular water changes help remove excess nutrients and waste products that can build up in the tank. I recommend changing 20-30% of the water every week or more frequently if necessary.
  • Test Water Parameters: Testing the water parameters regularly can help identify any issues before they become a problem. Test for ammonia, nitrite, nitrate, and pH levels at least once a week.
  • Monitor for Ammonia Spikes: Ammonia spikes can occur in a quarantine tank due to the presence of new fish, uneaten food, or decaying plant matter. It is important to monitor ammonia levels closely and perform water changes as needed to keep levels in check.
  • Maintain Proper Filtration: A good filtration system is responsible for maintaining water quality in a quarantine tank. Use a filter that is rated for at least twice the volume of the tank and clean or replace the filter media regularly.
  • Use a Siphon to Remove Debris: A siphon can be used to remove debris from the bottom of the tank during water changes. This helps prevent the buildup of waste products that can harm fish.

By following these tips, you can maintain optimal water quality in your quarantine tank and ensure the health and well-being of your fish.

Treatment in hospital tank

Medication and Treatment For Quarantine Fish

Medication is often necessary to treat sick fish.

Medications can help combat bacterial, fungal, and parasitic infections that may be affecting your fish.

But medications need to be used correctly and with caution.

First and foremost, it’s really important to properly diagnose the issue before administering any medication.

This can be done by observing your fish’s behavior and physical symptoms.

Once you have identified the problem, you can choose the appropriate medication.

There are many different medications available on the market, each designed to treat specific ailments.

Carefully read the instructions and follow them closely to ensure the medication is effective and safe for your fish.

When medicating your fish, it’s recommended to do so in a quarantine tank.

This will not only prevent the spread of disease to other fish but also allow for easier observation and monitoring of your fish.

Please note that not all medications are safe for all species of fish or aquariums.

Some medications may be harmful to certain species or may negatively impact the overall health of your aquarium.

Always do your research and consult with a professional before administering any medication to your fish.

Observation and Monitoring

One of the reasons for having a quarantine tank is so that you can monitor and keep an eye on how your fish are doing.

Visually inspecting the fish for any signs of illness, such as discoloration, abnormal behavior, or physical abnormalities is much easier when the fish are in a smaller dedicated fish tank.

Check on the fish daily to ensure that they are healthy and that there are no signs of illness or stress.

By observing and monitoring them closely in a quarantine tank, we can catch any potential issues early on and take the necessary steps to treat them before they become a bigger problem.

Emergency Quarantine

Emergency Quarantine Measures

In some cases, emergency quarantine measures may need to be taken to prevent the spread of disease in your aquarium.

These measures may include:

  • Removing sick fish from the tank and placing them in a quarantine tank immediately
  • Disinfecting all equipment used in the infected tank before using it in another tank
  • Removing injured fish that have been bullied so that they can recover in peace.
  • Isolating new fish in a quarantine tank before introducing them to the main aquarium
  • Treating the infected fish with medication as directed by a veterinarian or fish expert

It is important to act quickly and decisively when an emergency arises to prevent the spread of disease and protect the health of your fish.

For this reason, it is advisable to have a quarantine tank set up and ready to go at all times in case of an emergency.

Can I add fish directly to my main aquarium without quarantine?

Adding fish directly to the main tank without quarantine might set you back in fish keeping, as it risks introducing fish disease to the entire display tank.

How long should sick fish be kept in a quarantine tank?

Sick fish should be kept in a quarantine tank until they have fully recovered and are no longer showing any symptoms of illness. This can take anywhere from a few days to several weeks, depending on the severity of the condition.

Wrapping Up

In the world of fishkeeping, a quarantine tank isn’t just an optional accessory; it’s a vital necessity.

Think of it as a safety net for your aquatic friends.

When introducing new fish to your main aquarium, a quarantine tank acts as a protective barrier, ensuring that diseases and parasites are kept at bay.

It’s a space where new fish can acclimate, and sick fish can recover, away from the others.

For beginners and seasoned fish keepers alike, the quarantine tank is a tool that promotes a healthy and thriving aquatic environment.

It’s about being proactive rather than reactive, taking the necessary steps to protect the delicate balance of your aquarium.

Without a quarantine tank, you’re risking the well-being of your entire fish community.

It’s not just about preventing illness; it’s about fostering a stable, stress-free environment where your fish can flourish.

So, if you’re serious about fishkeeping, investing in a quarantine tank is not a choice; it’s a responsibility.

It’s a small step that makes a big difference, ensuring that your aquarium remains a vibrant and safe haven for all its inhabitants.

What Now?

Now that your quarantine tank is set up and ready for it’s occupants go ahead and read how to properly acclimate your new fish.

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Irma Bense is the founder of She has over 42 years of experience in keeping fish.She has kept both freshwater and saltwater fish through the years.She has extensive knowledge in breeding numerous species of fish from Show Guppies, Cory Catfish, German Blue Rams to Apistogrammas.You can learn more about Irma on the 'About' page.

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