6 Steps to Quarantining New Fish Properly (The 2022 Guide)

Quarantining new fish is one of the most important, and most often overlooked, aspects of raising fish. It is important to discuss why you should quarantine your new fish and what you should do if you have introduced new fish without quarantining them. There are several items you will need to quarantine your fish and the steps to follow to properly quarantine new fish. Let’s get started!

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Why Should I Quarantine My New Fish?

The first step in quarantining new fish is understanding why you need to quarantine your new fish. Quarantine is a good practice, no matter where your fish come from. It is very common for fish in large-scale breeding operations to be exposed to diseases and parasites such as ich, worms, and fish tuberculosis. Some diseases can occur in even the most high-quality breeding environments, so no new fish is guaranteed to be disease-free. Diseases are more common in places like large breeding facilities and big box pet stores, but they can occur anywhere.

Failure to quarantine your new fish can result in the introduction of difficult-to-treat diseases into your tank. Some parasites and diseases are very annoying or scary, while others are very deadly. Choosing not to quarantine your fish before introducing them to your aquarium can jeopardize the health and well-being of your entire aquarium. It may sound difficult to quarantine all new fish before bringing them into your aquarium, but it is a much better option than the alternative of having to treat the entire tank to illness and potentially losing fish in the process.

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What If I’ve Introduced New Fish Without Quarantining?

If you’ve introduced a new fish to your tank without quarantining it, don’t panic! You still have the option of keeping your aquarium healthy. Your first option is to do nothing, especially if the new fish have been in the tank for several weeks. You may choose to monitor the tank closely and watch for signs of disease in your new or old fish. This means you notice symptoms such as pinched fins, difficulty breathing, rapid breathing, sores, lethargy, white dots on the fins and scales, redness, fins jagged or torn, and inability or difficulty eating.

You can also go ahead and treat your entire tank with broad spectrum treatments to eliminate the threat before you notice symptoms. This includes using salt, antiparasitic, antifungal medications, or antibacterial treatments. Treating your tank without seeing any symptoms of disease, or treating it prophylactically, can help ensure a contagious infection doesn’t gain a firm foothold in your tank and begins to multiply. The earlier you treat the problem, the better, and not all diseases have visible symptoms in their early stages.

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goldfish in the tank

What Items Do I Need to Quarantine Fish?

Quarantine Tank

Your quarantine tank should be completely separate from your main tank. A tank divider or breeder box will not meet quarantine requirements. These tanks must have proper filtration and, if possible, be fully recycled before bringing any fish home.

Tank Cleaning Equipment

Supplies to carry out water changes are required for the quarantine tank as the fish will be quarantined for at least a few weeks. If the tank is not recycled, this is even more important. You want a separate supply for your quarantine tank, so you don’t accidentally transfer water from the quarantine tank to your main tank.

aquarium salt

It can be added directly to the quarantine tank or used in a separate bath for your fish. It can be used to treat ich and some other diseases as well as parasitic infections. It’s important to know that aquarium salt doesn’t evaporate with water, so if you keep adding salt without changing the water, you’ll end up with a high concentration of salt that may not be safe for your fish.

goldfish in fresh water_ luckypic_Shutterstock

Anti parasite

You will need this to treat any external parasites your fish may have brought home. Ideally, you would use this as a prophylactic. Hikari PraziPro and Seachem ParaGuard are both great options. ParaGuard can also be used to treat external fungal, bacterial, and viral infections. You’ll also need something effective against internal parasites, like Seachem Metroplex which can be used to make medicinal foods, as well as regular 3% Epsom salt.

Antibacterial / Antifungal / Antibiotic

You don’t need something like this for prophylactic use with new fish, but it’s a good idea to have one, just in case symptoms start to show. Seachem Kanaplex is a great choice for a broad spectrum antibiotic that can treat internal infections and can also be used to treat fungal infections.

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Water Test Kit

If you already have an established tank, you should already have a reliable water test kit. If you don’t have one, you need to invest in one that will allow you to check pH, ammonia, nitrite, and nitrate levels. This is especially important for non-recyclable tanks. The API Master Freshwater Test Kit is one of the most trusted products on the market for reliable test results.

API Freshwater Aquarium Master Test Kit

Water Treatment Products

Any water you add to your tank needs to be treated to remove chlorine and chloramines. It’s a good idea to stock up on products that can also help you neutralize waste products like ammonia. Seachem Prime neutralizes ammonia, nitrite, and nitrate, removes chlorine and chloramines, and helps support a healthy mucus layer.

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6 Steps to Quarantine Fish Properly

1. Tank Setting

Make sure your tank is full before adding new fish. Your filter should work properly, and the water should be well aerated.

2. Monitoring Parameter

Check your water parameters regularly with a test kit. If your quarantine tank is not recycled when you add new fish, then you should check the water parameters daily and treat the water appropriately to help remove or neutralize toxins. If the tank is completely recycled then you can monitor the water parameters every few days just to make sure everything is going according to plan.

holding a PH test in front of a freshwater aquarium

3. Treating External Parasites and Infectious Diseases

Once your fish have had a day or two to settle in the quarantine tank, go ahead and treat them with an external anti-parasitic medication, such as PraziPro or ParaGuard. Follow all directions thoroughly and perform the water changes recommended on the product label. Be aware that if the fish you are bringing home are already sick or weak, then any treatment you provide could be causing too much stress and killing them. This is an unfortunate risk that needs to be taken to make sure the fish are good enough to add to your main tank.

4. Add Aquarium Salt

Do not start adding aquarium salt until you have completed the previous steps. Once you have completed the previous treatment and made the necessary water changes, you can start adding aquarium salt. Aquarium salt is a great treatment for fighting ich disease and can help prevent it from getting into your main tank. However, aquarium salt is harmful to plants and invertebrates, so it should be used in quarantine aquariums.

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For tropical and sensitive fish, you will use a 0.2% aquarium salt concentration starting with 0.1% on the first day and another 0.1% on the second day. For stronger fish, such as goldfish, you will use a 0.5% aquarium salt concentration with 0.1% added to the tank daily for 5 days. Dissolve the salt in the water before adding it to the tank. Remember to add back the appropriate amount of salt for what may have been removed each time you do a water change. Maintain your salt concentration for 2 weeks.

5. Treating Internal Parasites and Infectious Diseases

After you have completed the salt treatment in your aquarium, perform water changes for several days to remove as much salt as possible before you start the drug treatment. Treating internal parasites and infectious diseases is an optional step in the quarantine process, but is recommended. Use broad-spectrum medications that can treat bacterial, viral, fungal, and parasitic infections.

6. Move Your New Fish

After these steps, your fish are ready to move into their new home! The quarantine process should last at least 2 weeks, but can easily last 4 weeks or more. Don’t rush the process. You want to make the quarantine period as safe as possible for your new fish and you want to quarantine them properly for the safety of your current fish.



Quarantining fish is a time-consuming process, but it will be worth it in the end. Bringing in new fish can be stressful for you, new fish, and your current fish, and quarantine helps make sure everyone is happy and healthy. It’s very common for fish to come from pet stores or breeders with parasites or diseases. Sometimes, you may not even notice symptoms of the disease until several days or weeks have passed. Quarantine allows you to pay attention to these signs and symptoms, as well as treat prophylactically before disease strikes.

Featured Image Credit: Pixabay

6 Steps to Quarantining New Fish Properly (The 2022 Guide)
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