How Long To Acclimate Fish 101: A Guide To Safe Fish Transfer

Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: July 6, 2024
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A frequent mistake when adding a new fish to your aquarium is rushing through the process. Although it might initially appear more efficient, failing to give your fish time to gradually adapt to their new surroundings can lead to illness or even death. If this seems alarming, it’s crucial to understand that the acclimatization process is simple and just requires some knowledge and patience. New aquarium enthusiasts, there’s no need to worry! We have gathered all the vital information on fish acclimation in one straightforward article.

Article Summary

  • The acclimation process involves allowing the fish to adjust to new water conditions, including temperature, pH balance, and other water chemistry factors.
  • The recommended time for acclimation is typically between 30 minutes to an hour.
  • When adding new fish to an aquarium, it’s advisable not to exceed adding more than three fish at once and to allow the nitrogen cycle to stabilize before adding more.

How Long to Acclimate Fish

Is there a definite answer on how long to acclimate fish? Well, some sources would say as little as 15 minutes can be enough time for your aquarium fish to adjust to its new home, but we recommend giving the process about an hour total.

This may seem excessive, but that extra time is worth it for the overall health and wellbeing of your fish, especially if they have experienced a lengthy journey during the travel or fish shipment.

Why is Fish Acclimation Important?

Moving Fish To New Tank
Moving Fish To New Tank

Acclimation is an important process because in all likelihood the conditions of the pet store water that your new fish has been living in varies from the aquarium water inside of your fish tank.

This variety includes important water chemistry factors such as water temperature, pH balance, and the presence of nutrients within the water itself.

What Happens If You Don’t Acclimate Fish?

If you don’t let your fish acclimate to your aquarium, and just dumping the whole bag in the aquarium are two sure ways to damage the health of the new fish as well as other fish species that are already in the tank.

The water that comes from the pet store can contain diseases and illnesses that are not wanted in a healthy main aquarium, and not taking the time to properly change this water for new fish can expose other fish to new diseases and health risks.

new fish can suffer shock when suddenly exposed to new conditions…

Most fish are incredibly sensitive to rapid changes in water parameters which means new fish can suffer shock when suddenly exposed to new conditions.

This shock of new conditions can stress your fish to unhealthy levels, meaning if it doesn’t die outright it will be more susceptible to disease and illness. Failure to acclimate your new fish could result in having to dispose of dead fish instead of having a new fish in the tank.

How to Acclimate Fish

There are two primary methods used when acclimating new aquarium fish to their new tank.

These methods are the floating bag method, and the drip acclimation method. Each has their own required steps and procedures for acclimating fish and are applicable to both a saltwater aquarium or freshwater aquarium.

Floating Method

Person Holding Fish Inside a Plastic Bag
Person Holding Fish Inside a Plastic Bag

Things You’ll Need

  • Bucket
  • Scissors
  • Timer
  • Towel or rag to wipe up potential spills
  • Measuring Cup


1. Prepare

Always the first step in any aquarium process!

Be sure to research the required water parameters for the fish you’ve just bought, and know what current conditions are like in your tank water. As an extra step, wash your hands to remove any excess dirt or harmful chemicals that can get into the water.

2. Adjust the Light

A great way to keep things comfortable for the fish and reduce stress.

Similar to changes in water parameters, sudden changes in aquarium lights can send your fish into distress.

A dim environment allows your fish to properly acclimate without worrying about sudden exposure to changes in light.

3. Float the Bag

Floating the sealed bag on the surface of the water for between 15 minutes to an hour allows the temperature of the water in the bag (and the fish by extension,) to safely reach the same temperature as the water in your aquarium.

Floating the bag this way also allows you to determine if there are any leaks in the plastic bag, in which case you should remove the water asap and transfer your fish.

4. Open and Roll the Top Edge of the Bag

Use your scissors to cut open the top of the bag around one inch from the top and fold it over, creating an air pocket which will allow the plastic bag to float.

5. Add Aquarium Water to the Bag

Add around a quarter to a half a cup at a time of aquarium water into the bag, repeating every 5 minutes until the bag is full.

6. Partially Drain the Bag

Once full, discard half the water in the bag as carefully as possible and without harming your fish. Gently lift the bag.

7. Repeat

Repeat steps 5 and 6 including the floating process, adding water to the bag a quarter to a half cup at a time until it is entirely full.

Once again, discard half the water in the bag before finally removing your new fish from the shipping bag.

8. Release the Fish Into Your Aquarium

Release your fish into the aquarium to join your pre existing community as the newest member of your aquatic family!

9. Pour Out Excess Water

Take the remaining water from the bag and pour it down the sink, not into the tank itself!

The fish store where you buy your new buddies is an excellent resource regarding just what water conditions will best suit your fish before adding them into your tank, be sure to check with them when you purchase!

Drip Method

Siphoning Water From Fish Tank
Siphoning Water From Fish Tank

Things You’ll Need

  • Bucket
  • Siphon hose, air tubing, and air valve
  • Metal clip, rubber band, or twist tie
  • Water stone or pump
  • Water conditioner
  • New fish


Most pet stores sell a complete drip acclimation kit, which can be a much quicker way to gather all of the required materials than trying to chase them down individually.


1. Prepare

As with the float method, a good recommendation is to start by contacting your local pet store about the conditions (such as temperature, chemical, and salinity parameters) that your fish will need to best make a smooth transition.

2. Add the Fish

Empty the filled shipping bag into the bucket and place it beside the aquarium tank you’ll be putting the new fish into. Add enough extra water so that the fish is sufficiently covered. 

3. Extra Oxygen

As an additional step if concerned about the amount of air in the water, add an air stone or air pump to increase the amount of dissolved oxygen and prevent pH shock in your new fish before transition. 

4. Removing Ammonia

Lowering ammonia levels by using an aquarium water additive or buffer may be a good consideration. Waste can quickly build up over the acclimating process through the natural nitrogen cycle and cause toxic shock to poison your fish.

5. Siphon

Set up your siphon, hose, and hose valve, allowing them to drip acclimate little by little. Use the air valve, clip, band, or tie loose knots to properly adjust the flow rate to begin acclimating your fish.

6. Check Water Level

Once the water level in the bucket has reached around one to two-thirds above what it originally was, measure the temperature, pH, and salinity to ensure that they have reached the same levels as those of your aquarium.

7. Transfer Water and Fish

When you see the pH, salinity, and aquarium water temperature acclimate to the same level as those in your tank, add your new fish directly to the tank using a small net and discard the extra water from the bucket.

As a bonus you’ll need to add more water to your aquarium to replace what dripped out while acclimating your fish, meaning you get a healthy partial water change in the process!

How Long Do Fish Need to Acclimate

Goldfish at a Corner of a Fish Tank
Goldfish at a Corner of a Fish Tank

For pretty much all fish species, the process of acclimation should take between 30 minutes and an hour.

Any longer can run the risk of the water in the bucket or bag become toxic as waste builds up, and any shorter and your fish may not be properly acclimated.

Can You Acclimate Fish Too Long?

While a good, careful acclimatization process is a slow process, you shouldn’t leave your fish in its separate quarantine tank for too long. This runs the risk of allowing excess wastes to build up, which can harm your fish through ammonia poisoning.

Floating Method vs Drip Method

While both methods are effective for both saltwater fish and freshwater fish, the methods differ primarily in their speed.

Floating Method

The floating method only requires the time it takes for both the water in the plastic bag and the tank to reach the same temperature as the aquarium water.

Drip Method

While the drip method uses a more time-consuming process to ensure that all water conditions are the same between the two over the course of 30 minutes to 2 hours, depending on how much water flow you allow for.

Should You Feed Fish After Acclimation?

A good rule of thumb is to watch your new fish. If the fish adjusts well and it is immediately active, there’s no reason not to feed.

We recommend starting small, with a little food at a time and close monitoring to ensure that the fish is actually eating.

This will prevent overfeeding and wasting food, which can lead to excess nitrogen building up in your tank.


While it is typical that most fish will not eat soon after reaching a new environment, the idea that they should not be fed for the first 24 hours is a general blanket statement to keep new aquarists from overfeeding and harming their aquatic life.


If the fish adjusts well and it is immediately active, there’s no reason not to feed. However we recommend starting small, with a little food at a time and close monitoring to ensure that the fish is actually eating.

This will prevent overfeeding and wasting food, which can lead to excess nitrogen building up in your tank.

How Long Should New Fish Sit in Bag?

Before putting fish into the aquarium, we recommend a temperature acclimation period of 15 minutes to an hour while letting the bag float (if using the float method).

This will allow you to acclimate your fish at a safe rate while you float the bag and avoid shock before they are added into your pre-existing community.

How Many Fish Can Be Added To A Tank At Once?

It’s perfectly fine to add more than one fish to your aquarium, but we recommend not exceeding 3 at once. After adding new fish, it’s a good idea to allow the nitrogen cycle to turn over a few times (around 24 hours) before continuing to add more.

Here’s a quick video on why you must avoid putting too many fish at once.

Adding Too Many Fish

Other considerations when adding multiple fish are that aggressive fish may need to be kept separate from others before they are introduced to the new environment to prevent damage between fish.

Also, certain freshwater species such as goldfish are known to produce large amounts of waste and may require the use of ammonia reducers prior to being added.


Acclimating your fish can seem like a daunting, tricky process at first, but with a little research and patience it can be quite easy!

Using either the drip or float bag methods is a great way to ensure that your fish has a safe, pleasant transition from the pet store to its happy home in your aquarium.

Safe Acclimation

Drip is the safer method for those with more available time to acclimate their fish, while the float bag method is simpler and easier for those wanting to get their fish up to speed and in their tank more quickly.

Feel Free To Share!

As always we hope that you’ve enjoyed today’s article and found the answers to all of your fish acclimation questions suitably answered.

Please feel free to share this with any other fish fanatics and fanciers in your life, and we wish you the best of luck on your continuing aquarium adventures!

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