How to Acclimate Fish: A Step-by-Step Guide

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Introducing new aquatic life to your tank is a delicate process that can’t be rushed.

The water conditions they come from are often different from your tank, affecting factors like temperature, pH, and salinity.

Quick changes in these factors can be harmful, especially for sensitive creatures like corals.

Here are two tried-and-true methods on how to acclimate fish and corals: the Floating Method and the Drip Method.

Floating Method: A Beginner’s Guide

Switch Off Aquarium Lighting

First things first, turn off the lights in your aquarium.

This helps to lower stress levels for your new arrivals.

Lower Room Lighting

Dim the room lights before you open the shipping box.

Bright light can be a shock to the system for these creatures.

Let the Bag Float

This is the most important step because the water in the bag will be a different temperature from the water in your tank.

Placing a fish in colder or warmer water without floating the bag first will cause the fish to be stressed and could even be fatal.

Place the sealed bag with your new fish or corals into the aquarium and let it float for around 15 minutes.

This helps to equalize the water temperature.

Create a Floating Mechanism

After the initial 15 minutes, snip open the bag below its metal clip or elastic band.

Roll down the bag’s top to form an air pocket, allowing it to float.

Introduce Aquarium Water

Slowly add about half a cup of your aquarium water into the bag every ten minutes until it’s full.

This helps the new arrivals get used to your tank’s water chemistry.

Remove Excess Water

Once the bag is full, take out half of the water and throw it away.

Do not put the water back into the main tank.

This minimizes the water volume without causing abrupt changes.

Continue the Process

Float the bag again and keep adding your aquarium water until the bag is again full.

Release Your New Friends

Use a net to gently move the fish or corals from the bag into your aquarium.

Make sure not to pour the shipping water into your tank.

Man holding a bag containing a betta fish

Drip Method: Slower but Better

Start with the Basics

Begin by following the first three steps of the Floating Method to balance the water temperature.

Move to Buckets

Pour the bag’s contents, including the water, into separate buckets meant only for aquarium use.

Make sure the fish or corals are fully submerged.

Set Up Drip Line

Use airline tubing to create a drip line from your main tank to each bucket.

Regulate the drip to 2-4 drips per second by using a plastic aquarium clamp or by tying a know in the tubing.

Begin the Drip

Initiate the drip by starting a siphon.

This slow drip helps the new arrivals adapt to your tank’s water conditions.

Discard and Continue

When the bucket’s water volume doubles, remove half, throw it away, and continue the drip until it doubles again.

Final Transfer

Once acclimated, gently move the specimens into your main aquarium.

Make sure to discard any shipping water.

A bag contained a single goldfish

Using a Quarantine Tank: A Safety Net

Set Up the Tank

Place the quarantine tank in a separate room and fill it with conditioned water or water from your main tank.

Read this article that I wrote on how to set up a quarantine tank.

Let the Tank Cycle

Allow at least a week for the tank to cycle before introducing new fish.

Acclimate and Observe

Use either the Drip Method or the Floating Method to acclimate new fish to the quarantine tank and observe them for any signs of illness.

Treat as Needed

If you notice any health issues, treat them with the right medications.

Final Step

Keep the new fish in quarantine for a minimum of three weeks before transferring them to your main tank.

If you are at all worried then keep the fish in the quarantine tank for a longer period.


Acclimating your new aquatic life is a vital part of ensuring their well-being in their new home.

Whether you choose the Floating Method or the Drip Method, the key is to be patient and attentive.

By taking these precautions, you’re setting your new fish and corals up for a successful life in your aquarium.

Photo of author


Irma Bense is the founder of She has over 42 years of experience in keeping fish.She has kept both freshwater and saltwater fish through the years.She has extensive knowledge in breeding numerous species of fish from Show Guppies, Cory Catfish, German Blue Rams to Apistogrammas.You can learn more about Irma on the 'About' page.

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