How to Acclimate Fish to Your Aquarium: Step-by-Step Guide

Rate this post

Coming home with a new aquarium animal purchase? Congratulations – this is the start of hopefully many long years of growth and enjoyment!

But have you considered how to add your new fish or invertebrate to your tank? As it turns out there are several ways to acclimate new fish into your home aquarium!

In this complete guide, we will walk you through exactly how to acclimate fish to your aquarium in the safest way possible.

How to Acclimate Fish to an Aquarium

You can acclimate your new fish using the floating or drip acclimation method. In this section we covers the details of each method and how to acclimate your fish safely.

Option 1: Floating Your Fish Bags

Temperature differences are the most common issue when acclimating new fish. While the pet store aquarium may be similar in temperature to your own during the ride home the bag has lost some heat. Simply thrusting the fish right into a new environment can be too much of a shock.

Instead one should float the bag inside the aquarium for 15 minutes to gradually warm it up. Once temperatures have equalized I always take things a step further by adding a small amount of aquarium water and waiting an additional 15 minutes and doing so a second time.

So long as the fish seems otherwise unaffected I then take a net and remove the fish from the bag, rather than simply emptying the fish with pet store water into the aquarium.

Never allow pet store water into your aquarium. Pet stores aquariums are constantly crowded and often have poor water quality. By adding that water to your tank you may be introducing a whole onslaught of viruses, bacteria, parasites, and fungal spores.

Adding a dose of Stress Coat once the fish is introduced will stimulate the production of a healthy slime coat. This boosts immunity and improves gill function while reducing the chances of your newest acquisition suffering from a stress-related disease.

Option 2: Drip Acclimation

If you suspect the pH or salinity are drastically different from your home aquarium or the organisms are especially sensitive (corals, starfish, stingrays, specialty fish), I recommend setting up a drip acclimation system.

In order to gauge how much the water chemistries differ you’ll need a Hydrometer for salinity (saltwater) as well as an Aquarium Master Test Kit to measure the pH, nitrates, and other parameters of the aquarium store water.

The drip acclimation method is very straightforward. Allow the bag to float as before until temperatures equalize. Next, gently pour the new animal into a clean bucket next to the aquarium. Using fresh airline tubing, tie 2 to 3 loose knots in the line that can be adjusted for flow control.

Place one end of the airline tubing in your aquarium and keep the other on hand. Suck water into the line until it passes the lip of the aquarium and then release the line into the bucket. You’re basically creating a siphon in the same fashion as a gravel vacuum.

Adjust the knots until flow slows to around 2 drops per second. Allow the water volume in the bucket to double in capacity and then discard half of this water.

Allow the water volume to double again, which should take around an hour or so. Now you’re free to add your new fish or invertebrates to the aquarium!

Tips to Minimize Stress On Your New Fish

Here are a few factors you should consider to help minimize the stress of acclimation:

Turn of any Aquarium Lighting

Turning off the aquarium lights for a while is better for new fish. Not only are they feeling shocked from transport but being constantly exposed under bright lights while floating doesn’t help.

Once the light is off introducing new fish is less likely to provoke a response from the current inhabitants, especially if they are of the same species. Fin nipping and aggressive displays are common greetings for slightly panicked new additions.

Minimizing Aggression from Other Fish

Acclimating new fish to an established tank means the social dynamics have been altered in a big way. Turning off the lights helps but there are quite a few other tricks that help your new addition find a place in the hierarchy.

Social species like Cichlids and Angelfish tend to carve out territories where intruders are challenged at the border. Since your new addition may not have a chance to find a turf of its own, rearranging the decorations levels the playing field a bit. Shift the placement of rocks, driftwood, and even fake plants when possible as all of these are territorial markers for the residents.

The dominant fish is likely the largest and will still be dominant once new territories are formed. However the fish lower on the totem pole won’t be as aggressive towards the new addition. And the newest fish now have a much easier time carving out their own space.

For some specimens using an aquarium divider may be best, especially if you’re trying to breed aggressive species like Bettas. By keeping the newly introduced female on one side, visible yet safe from the male, both fish can become accustomed to the sight of each other.

Fish also respond to chemical hormones which encourage the production of eggs and sperm. However many male fish in their eagerness can injure or kill unready females.

Using a Quarantine Tank

I strongly recommend keeping a quarantine tank on hand for acclimating sensitive, expensive species like Tangs and Discus. These fish are easily shocked by minute changes in water parameters.

If your home aquarium is radically different in chemistry from the pet store, even slowly dripping water into the bag may be too rapid a change. Wild-caught fish should always be quarantined in my opinion because they tend to have very high parasite loads that can kill them when combined with the stress of travel and their reluctance to eat prepared foods.

Quarantine tanks also allow you to give wild and/or sensitive species space to put on weight without having to compete with established residents for food and real estate. Medications are easier to dose and provide without negatively impacting your fish or beneficial bacteria.

You can make adjustments slowly, over the course of weeks if necessary, to pH, salinity, temperature, and other conditions until they match your main tank. Once your newest fish is acclimated to these conditions and eating the same food as the other fish you’re safe to move them right in!

Just remember that turning off the lights and rearranging decorations is still helpful if the other inhabitants are territorial or aggressive.


Acclimating new fish is something we all will do as aquarists from time to time. While most fish can be easily floated and introduced sometimes we need to put in a little more effort to accomodate sensitive species.

And when working with difficult fish it always pays to have a backup quarantine tank on hand for gently acclimating them to their new home!

You are viewing this post: How to Acclimate Fish to Your Aquarium: Step-by-Step Guide. Information curated and compiled by along with other related topics.

Leave a Comment