Safely Acclimating and Introducing New Fish to an Aquarium

how to introduce new fish to your aquarium written beside a young boy doing just that

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Whether you are just setting up your first aquarium, or have a much loved established one at home, getting a new fish is a very exciting time.

However, before you get wrapped up in the excitement of introducing new fish to an aquarium, it’s important you remember to properly quarantine and acclimate it so it stands the best chance of thriving in your tank.

Why Must You Acclimate New Fish?

Let’s be clear about this from the start…there’s no point in buying new fish if you’re going to endanger it, or the lives of your other fish, by tipping your newest addition straight into your established tank without thought or care.

Properly acclimating a new fish to your aquarium means being patient and following a logical, planned procedure to make sure they aren't shocked or stressed, and also that they don't bring disease or parasites into your established healthy tank.

So please, make sure you don’t bring a new fish home unless you have the time to help it survive during the crucial hours of acclimatization.

It Should Begin With a Stress Free Journey Home

The responsibility of giving your fish the best chance of survival starts as soon as you leave the pet store. Before you even get home, remember that the journey time and the journey itself can all take a toll on the stress levels of your new fish.

Try to keep the fish in a dark environment on your way home to stop the visible movement of the journey from being stressful for them. They’ll have got used to being in the tank at the pet store, so lots of different lights and colors may overwhelm them.

The other point to remember, is to make sure you head straight home once you have your new fish, as leaving them in the bag will cause a build-up of ammonia (from the fish's waste) which is harmful to your fish.

Why Can't I Tip a New Fish Straight Into My Tank?

Keeping the water from the pet store’s tank separate is very important when adding a new fish to your tank.

The reason you can’t just tip the fish in is the water from the aquatics store will then get mixed into the water of your tank, which is likely to have very different PH levels, hardness and trace elements in the water - among other things.

By simply tipping your new fish into your aquarium, you’re endangering the new fish, but also the rest of the fish who are already established in your home tank’s environment and very specific water qualities. You don't want any unnecessary sudden changes.

Also, although unlikely, it does sometimes happen that water from a local fish store carries parasites or disease that would be added to your tank. The risk is low, but it's a risk that's entirely avoidable, so avoid it you should.

Using a Quarantine Tank

This is a big topic that really needs an article of its own, but just as a quick reminder, we wanted to cover the basic principal behind quarantine tanks here.

Wherever possible, you should always use a quarantine tank for any new fish or plants you want to add to your aquarium.

The idea is to home your fish or plants for 4 to 6 weeks to make sure there are no parasites present (4 weeks tropical, 6 weeks cold water to cover the fact the life cycle of parasites is slower in colder water.)

While this may sound unnecessary to some owners, once you have experienced an outbreak of disease in your tank, you’ll quickly realize just how important it is to make sure all fish and plants are healthy before you let them live alongside your established, healthy tank community.

Testing the PH Balance

It’s perfectly acceptable to ask the aquatics store to test the PH balance of the tank your fish has been living in before you leave, as they should do this fairly regularly anyway as fish are bought and new fish are introduced.

If you don’t want to ask the store to test the water for you, it’s worth doing it yourself when you get home, testing the water you transported them home in. Remember to test your own tank too so you can tell how different the levels are in the water.

Once you know what the difference is in the PH levels, you’ll have a rough idea of how long the acclimating process will take. A big part of acclimating your new fish, is that you’re trying to avoid PH shock, which can kill fish in severe cases.

As a guideline, you need the PH levels to be very close together (a maximum of two tenths apart) for the process to take less than an hour. If the balances are more than 0.5 apart, then the process of acclimating your new fish should be done slower to ensure the risk of PH shock is brought right down.

What Method Should I Use to Acclimate My New Fish?

There are a few different methods that can be used to successfully ensure a new fish has a successful transition into your home aquarium.

Here are 3 different techniques that range in difficultly, effectiveness and safety, that can be done with various levels of equipment - Which method you choose is entirely up to you.

Bag Floating Method

This is the most common method used when acclimating new fish to a home aquarium environment, and is very popular as it needs only very basic equipment.

What Do I Need?

  • Small measuring cup
  • Fish net

How Do I Do It?

  • Before opening the bag, turn off your aquarium lights and float the sealed bag in your tank for 10-15 minutes. This time will allow the water in the bag to slowly adjust to the same temperature as the one in your tank.
  • Open the top of the bag, and roll it down several times to trap air into the top section; this will allow the bag to float.
  • Remove about 25% of the water in the bag, and replace it with the same amount from your tank.
  • Using your measuring cup, slowly add cups of water from your aquarium to the bag. If your PH levels were very similar (less than two tenths different), you may be able to add water every 5 minutes. If the levels were very different, allow 10 minutes between adding each new cup.
  • Continue to add aquarium water to the bag for around an hour. If the bag becomes full before this time, you may need to briefly lift the bag out of your aquarium and remove around half of the water before re-floating it and beginning the process of adding cups of water again.
  • After an hour, or slightly longer if the PH levels were very different, the fish is ready to be added to your aquarium. If you can net the fish in the bag without harming it, this is the quickest way to complete the process. If you’re unable to net the fish in the bag, remove the whole bag and tip it into a clean bowl so you can net it from there instead.

Bucket Method

This is very similar to the bag floating method, but is designed to help people who are concerned about spilling water from the bag into their home aquarium.

The issue with this method is it’s very hard to maintain the same temperature in the bucket as in your tank.

What Do I Need?

  • Small measuring cup
  • Fish net
  • Thermometer

How Do I Do It?

  • Measure the temperature of your home aquarium, and then fill a clean bucket with water of the same temperature.
  • Float the sealed bag in your tank for 10-15 minutes. This time will allow the water in the bag to slowly adjust to the same temperature as the one in your tank.
  • Open the top of the bag, and roll it down several times to trap air into the top section; this will allow the bag to float.
  • Carefully place the bag into the bucket so it floats on the top of the water.
  • Remove about 25% of the water in the bag, and replace it with the same amount from your tank. Make sure that no water from the bucket enters the bag, as you need your fish to acclimate specifically to the tank water.
  • Using your measuring cup, slowly add cups of water from your aquarium to the bag. If your PH levels were very similar (less than two tenths different), you may be able to add water every 5 minutes. If the levels were very different, allow 10 minutes between adding each new cup.
  • Continue to add aquarium water to the bag for around an hour. If the bag becomes full before this time, you may need to briefly lift the bag out of your aquarium and remove around half of the water before re-floating it and beginning the process of adding cups of water again.
  • After an hour, or slightly longer if the PH levels were very different, lift the bag from the bucket, and float it in your aquarium. This will allow time to ensure the water is still the same temperature in your tank.
  • If you can net the fish in the bag without harming it, this is the quickest way to complete the process. If you’re unable to net the fish in the bag, remove the whole bag and tip it into a clean bowl so you can net it from there instead.

Drip Method

Using the drip method requires more attention and equipment than the previous two options, and as it’s considered more advanced, it’s only generally used for more sensitive fish, for example starfish or shrimp.

If you’re concerned about whether you need to use this method for a particular fish, make sure you ask at the aquatics store before you head home.

What Do I Need?

  • Bucket (clean, and specifically for use only with your aquarium)
  • Airline tubing
  • Airline holder
  • Cup
  • Net

How Do I Do It?

  • Before opening the bag, turn off your aquarium lights, and float the sealed bag in your tank for 10-15 minutes. This time will allow the water in the bag to slowly adjust to the same temperature as the one in your tank.
  • Carefully open the bag, and tip it very gently and slowly into the clean bucket. If there isn’t enough water in the bag to fully cover the fish once it is in the bucket, you may need to slightly tip the bucket for a while, until the water level in the bucket has risen enough to accommodate the fish. Make sure you KEEP THE BAG somewhere clean, as you’ll need to use it again later.
  • Place the bucket near your aquarium, but make sure it’s at a lower level to allow the siphon to work.
  • Create a siphon drip line using the tubing, which runs from your aquarium to the bucket. If you don’t have a control valve, you’ll need to tie some lose knots in the tubing to help keep the flow of water regulated.
  • Use the airline holder to make sure the tubing is secure throughout the process.
  • To start the water running through the siphon, you’ll need to gently suck the end of the tube…obviously try not to swallow any of your aquarium water when you do this!
  • Once the water is running, place the tubing into the bucket. You can now either use your control valve, or tighten one of the knots you made earlier to help control the flow of water. The speed you are looking for is around 2-4 drips into the bucket every second.
  • Wait until the water level in the bucket has doubled, then carefully remove around half the water using the cup (make sure you don’t accidentally touch your fish with the cup at this point).
  • Allow the siphon to double the water level again, making sure you’ve given the process around an hour in total.
  • Using the bag from the aquatics store, scoop the fish out of the bucket, making sure you also have some of the water from the bucket in the bag (enough to entirely cover the fish).
  • Place the bag into your aquarium, allowing it to be submerged in the water. Once the bag is submerged, move the fish into the aquarium…if it doesn’t swim out of its own accord, you can use the net to guide it at this point.
  • Twist the top of the bag while it’s underwater, creating a basic seal. Remove the bag from the aquarium, and dispose of the water inside it. During this last part of the process, a small amount of water from the bag will transfer into your aquarium, but because the water from the fish store will have been diluted by your own aquarium water, this shouldn’t cause an issue (particularly if you have used a quarantine tank first).

Dealing With Aggressive Fish

Sometimes, adding a new fish to an established aquarium may lead to some of the older fish becoming territorial.

One thing you can do to limit this possibility is to move some of the decorations and non-rooted plants around the tank before you bring your new fish home. This can help to disrupt any current territories of fish in your tank, and will help make them more accommodating towards new roommates.

If you still have an issue with aggression from your current fish, the best thing to do is use a clean kitchen colander or other objects to section off the aggressive or territorial fish for a few hours.

It’s important not to section off the new fish, as you need to make sure they’re unstressed and can explore their new home fully.

Key Points to Remember

  • Diseases do spread very easily in aquariums, so always try to use a quarantine tank before moving your new fish into its ‘forever home’.
  • Some fish may appear lifeless when you bring them home, but do continue with the acclimating process anyway, as most of the time the fish will be completely fine once the process is completed.
  • Make sure you turn off your aquarium lights before adding a new fish to your tank, and leave them off for at least a few hours once they’re in there. This helps prevent their senses becoming overwhelmed and can go toward avoiding some stress.

Conclusion

The most crucial thing to remember about this process, is introducing a new fish to your tank does take a bit of time, so you need to be prepared and free to dedicate the necessary time on the day you bring your fish home.

By properly acclimating a fish to its new environment, you’re giving it the best chance of not only surviving, but thriving in its new environment. So take your time, and then enjoy watching the latest edition to your tank as it confidently settles into it's new home.

Happy fish keeping!​

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