Best Way To Transfer & Introduce Fish To New & Established Tanks

Estimated read time 9 min read

Transferring Fish To A New Tank

Introducing fish to a new tank will require some effort from your end.

It might seem easy to add new fish to your tank right away, but if you do that, you’ll be asking for a whole bunch of problems.

Fish are sensitive creatures, mindful of their habitat. Change is not received well by most fish.

Well – Not unless you do it right.

It would help if you kept a few things in mind while transferring fish to a new tank.

Even little things like slight differences in pH levels between their original tank and the new tank can make for a terrible experience for your fish.

If you don’t do it right, you can compromise the health of your new fish and even cause them to die.


Best Methods To Transfer Fish To A New Tank

Here are a few methods to ensure your fish transfers to a new tank as smoothly as possible.


Acclimation to a new tank is the most crucial part of the process and gradually acclimatizing your fish to their new water parameters can help them adjust better.

To ensure an easy transfer, note the conditions of the tank you will be adding the new fish to—things like pH levels, temperature, lighting, etc.

You’ll want to mimic these things as you acclimatize your new fish.

Below we’ll get into the different methods you can use to acclimatize your fish; using a bag, quarantine tank, drip acclimation, or a small container.

You can also try to keep the lights off for a few hours after adding your new fish.

If the new tank has a few hiding spots, it can help your new fish feel less threatened by the new environment.

Quarantine tank

A quarantine tank is one of the best ways to acclimatize your fish and makes the transfer to a new tank safer.

A quarantine tank is usually a small tank that mimics the environment of another tank. This is generally accomplished by filling it with water, gravel, and even filter media from the main tank.

The quarantine tank allows your new fish to acclimatize to the new water parameters in peace while isolating them from other fish.

This is helpful in the event your new fish came with some new parasites or diseases that you don’t want to spread to your main aquarium.

The quarantine tank should be at least 5 to 10 gallons, with a sponge filter or filter media from your main aquarium. This will ensure the filter contains good bacteria to populate the tank.

The idea of a quarantine tank is to make the transfer less daunting for the fish. You can put decorations and gravel from the old tank into the quarantine tank.

Float the bag

Floating the bag is another method to acclimatize the fish to the new tank.

Most fish stores will send you home with your fish in a bag. You can add some water from the new tank into the bag when you get home.

Then, you can let this bag float in the new tank.

This helps the new fish acclimatize to the new water temperature while still being in some of their original tank water, easing some restlessness.

Gradually, add more water from the new tank into the bag every 15-20 minutes.

Once the plastic bag is full, let it float for another 20 minutes and then remove the fish from the bag with a net and transfer your fish to their new home.

While this method might be faster than using a quarantine tank, you have no way of knowing if your new fish is healthy and free of disease.

That said, everyone has added new fish to their tank using this method at some point.

Note: Be mindful that you don’t want to let any water from the plastic bag get into the new tank; it can contaminate your aquarium.

Drip Acclimation

Drip acclimation is somewhere in between floating the bag and a quarantine tank.

For this method: you would place your new fish with the water they came with into a bucket or small container.

Using a drip line with a valve, you start a siphon from the new tank into the bucket.

Set the valve to only allow a drip every other second and slowly let the bucket fill for about an hour or longer.

Note: be sure to pay close attention to the water level in the bucket if it fills faster than you expect.

After about an hour, you can use a net to transfer your fish to their new tank.

This method’s benefit is that your fish will very slowly be exposed to the new tank’s water parameters, which is excellent for sensitive species of fish.

That said, just like floating a bag, you have no way to tell if your new fish is healthy and free of disease.

How To Transfer Fish To A New Tank Without A Bag

If a situation arises that you don’t have at least a plastic bag, you can transfer your fish using a small container or a bucket.

If you transfer your fish at home, you can safely use a bucket or a smaller aquarium to transfer your fish.

How Long Should You Wait Before Transferring Fish To A New Tank

Eventually, fish will start running out of oxygen if kept in a bag or bucket without some source of oxygen.

It would be best if you did not keep your fish in a plastic bag or a closed container for more than twenty minutes without opening it up.

However, if you have ever ordered fish online, you know this can be stretched out; that said, it is not recommended.

Transfer time and excitement aside, do your best not to rush and add your fish to their new home too quickly and understand why you should wait 24 hours before adding new fish to a tank.

If you just set up a new tank, add liquid bacteria, conditioners, stress coat, decorations, plants, etc., and let it settle for at least 24 hours before you start adding any new fish.

This allows your new tank to become more stable before adding fish.

Adding New Fish To An Established Tank With Old Fish

Transferring New Fish Might Cause Them To Hide
New Fish May Take To Hiding After Being Transferred To A New Tank.

How Will The New Fish Behave

When you add new fish to an existing tank, it will likely feel scared and threatened by fish already in the tank.

Your new fish will find spots to hide as it acclimatizes itself to the new setting.

Your new fish might not eat for a few hours or even days as it adjusts.

Be patient check on them each day. A fish that has adjusted will be swimming around, looking energetic, and eating when the other fish eat.

Change is difficult on fish, and it’s your job to do the best you can to make the transition as easy on them as you can.

How Will The Old Fish Behave

The old fish may behave erratically or may welcome your new fish to the tank.

However, this depends on the existing species, how well they get along with the species coming in, etc.

But most importantly, how and when you feed your new fish after adding them to a new tank. can change their behaviors.

You can do certain things like feeding the old fish right before transferring a new fish or even move some decorations around.

This will take away the attention of the old fish from the new fish.

If you notice any aggressive behavior toward your new fish, watch closely; if your new fish gets injured or seems to be struggling, it might be best to remove them.

Place them into a quarantine tank and try again later.

Depending on your fish, you may need to try a few times.

How Many New Fish Should You Add At A Time?

It’s best to add new fish in small groups of up to 4 fish at a time.

This will help minimize the stress of the new fish. Moreover, it will help spread the existing fish’s attention, so the new fish don’t get overwhelmed by the welcome.

Adding fish in larger groups can overwhelm the tank’s beneficial bacteria that has grown to handle the existing bioload.

How Long Does It Take For New Fish To Adjust To A New Tank

The amount of time it takes for a new fish to adjust is entirely arbitrary. If the acclimation is done well and the transfer is not stressful, the fish will get used to the new surroundings sooner. If you do not acclimate the new fish well, it may even die.

If you bear in mind the transfer methods and tips shared earlier, the chances of acclimation will soon increase.

What You Should Do If Your Old Fish Are Dying After Adding New Fish

If your existing fish start dying, the chances are that your new fish came with some friends like bacteria, parasites, or some disease.

If this happens, it’s best to remove any sick fish and place them in quarantine along with your new fish.


Quarantining the new fish before you bring it into the new tank can help you identify any bacteria or diseases that it may carry.

This way, you can entirely avoid any fish death after the transfer.

Remove new fish

As soon as notice the fish is dying, immediately remove the fish from the tank and change the water.

Remove the new fish and any other sick fish and quarantine them.

Should You Complete A Water Change Before Adding New Fish

A complete water change is not necessary before adding new fish.

Water changes as much as 30% can help your new fish adjust well in the new tank.


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