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Home > Fish > 6 Steps to Properly Quarantine a New Fish: Vet-Approved 2024 Guide

6 Steps to Properly Quarantine a New Fish: Vet-Approved 2024 Guide

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Dr. Luqman Javed

Veterinarian, DVM

The information is current and up-to-date in accordance with the latest veterinarian research.

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Quarantining new fish is one of the most important, and most commonly ignored, aspects of keeping fish. It’s important to discuss why you should be quarantining your new fish and what you should do if you’ve introduced new fish without quarantining them. There are a few items you’ll need to quarantine your fish and steps to follow to properly quarantine new fish. Let’s get started!



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, regardless of where your fish are coming from. It’s extremely common for fish in large scale breeding operations to pick up diseases and parasites like ich, flukes, and columnaris.

Some diseases can occur even in the most high-quality breeding environments, so no new fish is guaranteed to be disease-free no matter how healthy they appear at time of purchase. Illnesses are more common in places like large breeding facilities and big box pet stores, but they can happen anywhere.

Failure to quarantine your new fish can result in the introduction of hard-to-treat diseases to your tank. Some parasites and diseases are pesky or creepy, while others are flat out deadly. Choosing not to quarantine your fish before introducing them to your tank can endanger the health and wellbeing of your whole tank. It might sound like a pain to quarantine all new fish before bringing them into your tank, but it’s a much better option than the alternative of having to treat an entire tank for illness and potentially losing fish in the process.

It is also worth noting that many diseases, such as ich, are entirely preventable with good quarantine practices.

photo of fish tank with orange and yellow fish
Image Credit: cruik, Unsplash

What Items Will I Need for a Fish Quarantine?

Quarantine Tank

Your quarantine tank should be a fully separate tank from your main tank. A tank divider or breeder box will not meet quarantine needs. This tank should have proper filtration and should be fully cycled prior to bringing any fish home.

Tank Cleaning Supplies

Supplies for performing water changes are necessary for a quarantine tank since the fish will be in quarantine for at least a couple of weeks. You want separate supplies for your quarantine tank, so you are not unintentionally transferring water from your quarantine tank to your main tank.

Aquarium Salt (Optional)

This can be added directly to the quarantine tank or used in a separate bath for your fish. It can be used to help treat some diseases and parasitic infections. It’s important to know that aquarium salt will not evaporate with water, so if you continue adding salt without performing water changes, then you will end up with a high salt concentration that may be unsafe for your fish. This may also cause them to suffer from acclimation shock when they’re placed in your community tank after their quarantine. Therefore, you should be careful when using aquarium salt and stay on top of your water changes. Aquarium salt should not be used when quarantine tanks include live plants, as it is very toxic for them, even when dosed properly for fish.

goldfish in freshwater_ luckypic_Shutterstock
Image Credit: luckypic, Shutterstock


You will need this to treat external parasites your fish may come home with. Ideally, you will use this prophylactically. Hikari PraziPro and Seachem ParaGuard are both great picks. ParaGuard can also be used to treat external fungal, bacterial, and viral infections.


You won’t necessarily need something like this to use prophylactically with new fish, but it’s a good idea to have on hand, just in case signs of illness begin to show. Seachem Kanaplex is a great option for a broad-spectrum medication that can treat internal infections and can also be used to treat fungal infections.

Water Test Kit

You should always have a reliable water testing kit at hand. If you don’t have one, you need to invest in one that allows you to check pH, ammonia, nitrite, and nitrate levels. This is especially important for an uncycled tank. The API Master Freshwater Test Kit is one of the most trusted products on the market for reliable test results. It’s also good to invest in a water thermometer alongside an aquarium heater, fan, or chiller (depending on what fish you adopt).

Water Treatment Products

Any water you add to your tank needs to be treated to remove chlorine, chloramines, and heavy metals. It’s a good idea to keep products on hand that can also help you neutralize waste products like ammonia. Seachem Prime helps neutralize ammonia, nitrite, and nitrate, removes chlorine and chloramine, and helps support slime coat health. Note that it doesn’t remove ammonia from your water, but only converts it to ammonium (which is also unsafe for fish, but not as toxic as ammonia).

fish in fish tank
Image Credit: Daniel Corneschi, Unsplash

The 6 Steps to Properly Quarantine a Fish

1. Tank Setup

Ensure your tank is fully up and running before adding any new fish. Your filtration should be functioning properly, and the water should be well-aerated. The aquarium should be cycled before you bring your fish home; this process takes up to 4-6 weeks.

2. Introduce Fish/Plants

When you first purchase your fish or live plants, add them to the quarantine tank. Fish should be gently acclimated for an average of 30-60 minutes before being added into the aquarium. Plants can either be added directly to an aquarium or given a bleach bath before being added in (to rid them of most snails and some algae).

A diluted bleach solution (1 part bleach to 20 parts water) should be used for such a dip. Please keep in mind that this dipping method will focus on ridding your plants of potential hitchhikers and prominent algae, but algae can still show up in your aquarium due to other factors. You should not dip the plants for an excessive length of time.

You may use the following guidelines:
  • Thinly leaved/delicate plants and plants with sensitive stems – 90 seconds (1 min 30 seconds)
  • Most other plants – 120 seconds (2 minutes)
  • Exceptionally hardy plants (Anubias species, Java Ferns) – 150 seconds (2 mins 30 seconds)

You should have a separate bucket with dechlorinated water ready before you dip your plants. Be sure the plants are thoroughly rinsed and soaked in the dechlorinating solution before adding them to your aquarium.

black and yellow fish in a fish tank
Image Credit: Lenstravelier, Unsplash

3. Treat for External Parasites and Infectious Diseases

Once your fish have had a day or two to settle into the quarantine tank, go ahead and treat with an external antiparasitic medication, like PraziPro or ParaGuard. Follow all instructions thoroughly and perform any water changes recommended on the product label.

Be aware that if the fish you’ve brought home are already sick or weak, then any treatments you give them may cause too much stress and kill them. In such a situation, you should consult your aquatic veterinarian for further advice.

4. Treat for Internal Parasites

Treating internal parasites is strongly advised during the quarantine period. Use a broad-spectrum medication that can cover bacterial, viral, fungal, and parasitic infections. This step can often be combined with the previous step, depending on the medicine you use. However, it’s best to have your veterinarian prescribe an appropriate medicine regimen for your fish.

5. Monitor Your Fish for 4-6 Weeks

After the broad spectrum treatments of your fish, the next few weeks are spent observing your fish for any signs of illness or disease and treating them accordingly. During this time, you should perform weekly partial water changes. These water changes might have to be increased in frequency if fish are being medicated for any ailment.

colourful fish in tank
Shutterstock | Andrey Armyagov

6. Move Your New Fish

After the quarantine period of 4-6 weeks has elapsed without any signs of disease, your fish are ready to move into their new home! The quarantine process should last 4 weeks at least, but it can easily last 6 weeks or longer. 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 properly for the safety of your current fish.

Important: if you notice any disease or ailment in your fish during the quarantine period, then you should treat them promptly (following your veterinarian’s guidance and instructions) and reset the quarantine “timer.” Fish should be disease and problem-free for at least 4 weeks before being added to your community aquariums.

divider-fish What If I Already Introduced New Fish Without Quarantining?

If you’ve already introduced new fish to your tank without quarantining them, you should go for the next best solution. This solution is to do nothing, especially if the new fish have already been in the tank for a few weeks. In essence, your best bet now is to roll with the risk and hope the fish you added to your aquarium were disease-free. The option to use prophylactic medicine in this scenario is done on a case-by-case basis and something you should discuss with your aquatic veterinarian.

You can choose to closely monitor the tank and watch for any signs of illness in your new or old fish. This means you’re watching for signs like fin clamping, difficulty breathing, rapid breathing, sores, lethargy, white dots on the fins and scales, redness, jagged or torn fins, and inappetence or difficulty eating.

a beautiful planted tropical freshwater aquarium with fishes
Image Credit: S-F, Shutterstock


In Conclusion

Quarantining fish is a time-consuming process but it’s worth it in the end. Bringing in new fish can be stressful to you, the new fish, and your current fish, and quarantining helps ensure everyone is happy and healthy. It’s extremely common for fish to come from pet stores or breeders with parasites or illnesses. Sometimes, you may not even see signs of illness until a few days or weeks have passed. Quarantine allows you to watch for these signs, as well as treat them prophylactically before illnesses take hold. 

Featured Image Credit: Ko Thongtawat, Shutterstock

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