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How to Acclimate New Aquarium Fish? (Complete Guide)

How to Acclimate New Aquarium Fish? (Complete Guide)

Acclimating fishes has long been a subject for discussion. Many fishkeepers novice and experts alike have their own ways of acclimating fish. 

But why is acclimating fish important in the first place? Well for starters, acclimating new fishes is one of the most important processes to learn correctly right from the get-go because acclimating fishes properly greatly increases their chances of survival in a new environment. 

In today’s article, we discuss a step by step guide as well as the different methods that hobbyists use for acclimating their fishes. 

Acclimating Fish

In this section, we cover a step by step guide on how we acclimate fish in our own tanks. This method can serve as a guideline for you to follow or you can easily tweak the method to your own liking but don’t worry, we’ll cover the important aspects so you’ll not miss a step! 

The Drip Method

We’ll start by covering what this method is. The drip method is, like its name suggests, consists of dripping water from your fish tank into the new bag of fish or fishes. 

This method holds the best success rates for us and many others because it slowly allows the new fish to get used to the new environment’s water. This is crucial because any sudden changes to an already stressed fish can cause shock and ultimately kill your fish!

For this method, you’ll need a few things. 

  1. A small bucket to place your new fish in.
  2. Airline tubing for dripping water into the bucket with the new fish
  3. 2 clothesline clips to fasten the airline tubing while it’s dripping water into the bucket. 


Now that we know what equipment we need, let’s dive straight into preparing for the acclimatization.

First, empty your new fish into the small bucket. And place it at a place that is lower than your tank. Having the bucket at a lower level than the fish tank is crucial if not the gravity feed from the airline tubing will not work. 

Second, tie a knot at the end of the airline tubing that will go into the bucket. This knot will reduce the water that is coming from the tank to a drip. How tightly you tie this knot will determine the amount of water coming through the tubing. 

Third, fasten the airline tubing to the tank and the bucket with the plastic clips.

If you’ve done everything above, it should look something like this! And then we can begin the acclimatizing process. 


The acclimatizing process is not difficult and depending on the amount of water, should take roughly between 1-1.5 hours. 

To start the siphon going, all you need to do is to either fill the airline tubing with water or you can suck on the end that is going into the bucket. A little dirty we know, but it works. 

Adjust the tightness of the knot such that the water comes out in a steady stream of drips. A good gauge is 1 drip a second and no more than that. 

Once the drip has started, you will need to monitor the drip so that the water does not overflow from the bucket. A good practice is to remove half the amount of water from the bucket once it’s almost full. 

When reaching the 1-1.5 hour mark, you can stop the siphon. During this process, it is also important to monitor the fish’s behavior to ensure that there are no signs of stress or onset of shock. 

If there are any signs of stress, stop the siphon. Continue observing the fish until it stabilizes before continuing. 

fish tank

Putting the fish into the new tank

If all goes well, you should have a very nicely acclimated fish that is ready to go into its new home. 

However just before you decide to dump your new fish into its new home, make sure that the new fish is in good condition and not in any stress. 

Then carefully net the fish and place it into its new home, continue to monitor the behavior of your fish especially if the new environment is a community tank. 

And that’s it! While drip acclimating might be a more tedious process than other methods, it is possibly the method that yields the best results. 

Also Read: How do Fish Poop and Fee? (and How Often?)

What Other Methods of Acclimating Fishes are There?

The other method that aquarists use often is called the ‘Float’ method. This method involves placing the bag of new fish into the current fish tank. 

Many hobbyist argue that this method is equally effective and drip acclimatization might be a little overkill. Like what we’ve mentioned above, this method involves placing the bag of new fish into the current tank for a period of time in order for the temperature of the water to equalize to that of the current fish tank, before releasing the fish together with its contents into the tank.

However, there are a few issues that we take seriously when it comes to acclimating new fishes.

Water from the fish store

If you don’t already know by now, fish stores tend to house hundreds if not thousands of fish, often kept within the same system. This causes an issue because, in the event of a disease outbreak, you would potentially be introducing unwanted pathogens into your fish tank. 

Even though the fish might look healthy when it was bought, there are instances where it can take days or weeks before any sign of disease shows up. And by then, it would be too late. 

Arguably, an infected fish that was dripped acclimated might have a disease, not pouring water from the fish store will greatly improve your chances of not infecting the rest of your tank inhabitants. 

Other parameters

Float acclimating only accounts for the difference in temperature and not for the difference in other water parameters, like pH, hardness, etc. While float acclimating does take away the temperature difference, the other parameters are forgotten but are equally important. 

Most fishes today in the aquarium trade today are relatively hardy, as such, these parameters might not affect them as much. However, there are fishes that are very sensitive to water parameters, especially if you are keeping marine fish where a large difference in salinity could kill them instantly.

Also Read: How Long do Guppies Live (Tips for Longer Life)


Generally, acclimating fishes is relatively straight forward. Follow the process and you should be fine. But, there are some tips you can keep in mind while doing so to maximize your chances of success. 

Slow and steady

Yes, we know, you’re excited to have your new fish in the tank. But take a step back and slow down. 

Rushing through acclimatizing not only puts your new fish’s life at risk but also risks the lives of the other fishes that are currently inhabiting the tank. 

Slowing down ensures that the new fish has enough time to get used to its new surroundings. 

Can you imagine if you somehow teleported to the top of Mount Everest this instant? Not only will you probably not survive, but you’re also most certainly going to die a slow painful death. 

This is why mountain climbers train hard and acclimate themselves to the climate and changes in air pressure before even attempting to climb. 

Only put what you need to put into your tank

This is so important. Time and time again, we’ve seen novice keepers acclimate their fish and empty the contents of the entire bag into their tanks. 

Like what we’ve discussed above, the water which comes with the fish often contains viruses and other pathogens that are undesirable to have in our tanks. Can you imagine an ich outbreak on your beautiful community tank? 

Not a very fun disease to handle. That’s why, to be safe, only put what you need to put in your tank, and nothing else.

Buy only healthy-looking fishes

As important as it is to acclimate your fishes properly, it is also important to choose fish that are healthy and without a disease. 

Always buy from reputable fish stores or stores that keep their fish in good condition. Any store that does not do so should not be patronized, no matter how appealing their fishes might be. 

Like what we’ve discussed above, unhealthy fish not only have a high chance of dying but also have high chances of spreading disease throughout your tank. 

So unless you want to spend a bomb on medication, we suggest buying only healthy-looking fish from reputable fish stores. 


In this section, we cover some of the more commonly asked questions when it comes to acclimating fish!

What happens if you don’t acclimate fish?

The problem with not acclimating fish is that while they may not necessarily die instantly, they might perish a slow and painful death due to the shock they experience, which can happen within a few hours or within a few days. 

Much like the mountain climber example we gave above, acclimation gives the fishes a chance to slowly break into their new environment. Acclimating fishes greatly increases the chances of your fish’s survival in the long run. 

Do you need to acclimate fish?

Absolutely! Not acclimating your fish almost always kills your fish if the water parameters are too different. 

Acclimating fish is not hard and should be a process that is familiar to all fish keepers novices and experts alike. Start early so you can have the best success rate possible in the future. 

How long do you leave fish in the bag before putting it in the tank?

There’s no set timing for how long you should float a bag in the tank before transferring the fish into the new tank.

However, a good gauge is usually 0.5-1 hour before attempting to put your fish into its new environment. Of course, for bigger bags, you might opt to wait longer for the temperatures to equalize. 

Also, it is important to note that you should always net the fish and not pour the contents of the entire bag into the new fish tank. 

How do you acclimate a fish that has been shipped?

With shipping fishes being more and more accessible within the aquarium hobby, it’s not a surprise someone asked this question.  Shipping is often a stressful ordeal for all parties involved, especially the fishes.

Imagine being cooped up in a small space for many hours sometimes days, eventually emerging in an entirely new environment. Pretty stressful eh? With these fishes, it is very important to take things slowly and ensure that all the steps of acclimating are done right. 

Much like what we’ve described in our guide above, drip acclimating is the best possible thing to do with an even slower drip rate than you would for a fish from the fish store. 

This is because stressed fishes tend to go into shock easily. In order to avoid these issues, reduce the drip rate so the fish can take its time to get used to the new water parameters.


Acclimating fish is a crucial skill that every fish keeper should know at the back of his or her hand.

Knowing how to do so properly not only dramatically increases the survival rate of new additions to your fish tank, but also ensures that your tank remains disease-free. 

Drip acclimating, which we’ve discussed at length is a simple yet effective method of acclimating fishes. Remember the tips we discussed as well, go slow, buy only what you need in your tank, and buy only healthy fishes.

We hope that today’s article was as informative for you as it was fun for us. Thank you for reading!