How to Acclimate Fish From One Tank to Another? (Full Guide)

If you are an owner of aquatic pets, you are no stranger to “acclimation.” Whether knowing or unknowingly, your aquatic pet has to go through this process every time you introduce them to a new environment. Doing this in the right way will be beneficial for your fish, and any wrong turn or impromptu acclimation can be fatal. 

So knowing how to acclimate fish from one tank to another is important if you want to keep your fish healthy, safe, and with a better life span. However, you have to go with this process when you introduce the newcomers and every time you are interchanging the aquarium animals, changing the water, or switching to a new aquarium. 

In this write-up, you will know how to acclimate fish in the most effective way, what you should know about acclimation, and so on. So let’s get into the main read without more delay.

What is Fish Acclimation?

Acclimation means the process of adjusting and habituating lives to new places and new environments. Aquarium fishes are tiny lives with different sensitive physiology. A sudden change in water parameters, new climate, and conditions can drastically affect their lives. Proper acclimation is the way by which you can make your fish adjust safely and beneficently to a new environment. 

Going through the process, fishes will be familiar with the new place. Additionally, it will help them adapt to conditions like water pH, temperature, mineral content, etc. 

How to Acclimate Fish from One Tank to Another? (Step by step) 

Acclimate your fish every time you bring new fish from a pet shop. Even when you are interchanging your existing fish from one aquarium to another. Here are the step-by-step processes to acclimate fish.

Step 1 

The first step of acclimating your fish is checking and ensuring the fish is completely disease-free. Also, you have to ensure the new place is appropriate for it. Every fish have a specified requirement of survival. You have to maintain them before starting to acclimate. 

Step 2 

In terms of acclimating newly bought fish to your aquarium, floating is the easiest and effective way to acclimate. All you have to do is float the fish bag, which comes as a plastic bag, into the aquarium you want to put the fish in. After that, leave the bag for at least 15 minutes. Within this time, the water temperature of the fish bag and aquarium will be the same. And the environment is primarily ready for your fish. 

Step 3 

Now grab a net or put the fish into the new aquarium, carefully using your hand. While using hand make sure to sanitize well. And observe the fish for the next 1 hour to ensure that your fish has been acclimated to the new place. 

Here are a few things you to be careful about, 

  • Don’t open the water bag before acclimation. It will release carbon dioxide, which is helpful for controlling the ammonium balance inside the bag. 
  • Don’t leave your fish in the bag for more than 6 hours. 
  • Make sure not to mix the bag’s water in the fish tank. 
  • To change existing fish into a new tank, take a small container, fill it with the water from the new aquarium, and leave your fish here for 15 minutes. If everything seems normal, then put them directly into the fish tank. Don’t forget to ensure step 1.

How Long Does it Take a Fish to Acclimate to a New Tank?

The amount of time it takes to acclimate a fish into a new tank is divided into two categories. 

The first one is the primary time, which is around 15 to 20 minutes. It is when you bring the new fish to the aquarium for the first time. This time is necessary for the primary level acclimation, like the temperature. 

Then comes the second phase, which can be long up to one hour. In this time, the fish completely adjust to the new environment, including the pH, ammonia level, oxygen level, and other important parameters that happen to be normal to your fish in this phase. 

What Happens If You Don’t Acclimate Fish?

If you don’t acclimate fish into a new tank in a proper way, it will be fatal for your fish. There is a physiological term called “osmoregulation,” which refers to the fish’s ability to balance its body’s water and salt ratio.

Without acclimation, you will experience different salinity in a short period. Thus could have caused an acute osmotic shock. And this can cause severe health deterioration to death to your fish.

Is It Bad to Switch Fish Tanks? 

The bad or good of switching fish tanks depends on the circumstance. Until the fish tank water is contaminated with any particular disease or toxication present, there is no need to switch. Cause repetitive acclimation will certainly affect the vitality of your fish.

Moreover, completely switching fish tanks leaves good bacterias behind. So when you are thinking of a switch, be more considerate and plan correctly. 

Should you Feed Fish After Acclimation?

It’s not mandatory to feed your fish right after acclimation. As well there is no embargo on feeding. You can say it’s entirely up to you.

If you get signals that your fishes are acclimated well and behaving normally like swimming and playing, you can offer them small feed to check their appetite and mood. After that, take the decision of feeding accordingly.

How Many Fish Can You Introduce at Once?

Introducing two to three fishes at a time is best. Putting them in a group will create a familiar environment like the previous one. However, if you’re planning to acclimate a bunch of fish, then plan to put them in regular intervals. 


Knowing how to acclimate your fish from one tank to another is important if you want to keep your fish alive and give them a good life. Also, it’s the best practice to maintain the environment of your fish tank and keep your other pet safe.

The acclimation process is easy and simple, but its effects are remarkable. So whenever you get a new aquatic pet or plan a better place for your fish, don’t forget to acclimate them in the right way. 

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