Introducing Your New Fish To The Aquarium

As Fishkeepers, we have a responsibility to provide the best possible care for our pets.

Moving home is a stressful event. It means a change in environment and unfamiliar surroundings. For fish, this change is even more of a shock. The chances are that the water in their new tank will have dozens of subtle differences from the previous one. These changes take time to adapt to and stress can make fish susceptible to illness.

Thankfully it is easy to reduce the stress of moving tank in just a few, easy steps!


Things to do before you add a new fish.

  1. The first thing to do is to check with your local fish store if the fish you have chosen is suitable. Also check if it has any unique requirements. For example: does it need live foods or is flake suitable?
  2. Always check what size the fish will grow to. It is all well and good deciding that you would like a cute baby red tailed catfish but can you house it as a 36″ adult? Aquatic stores are inundated with offers of large fish and seldom have room to accept them.
  3. Test your water. Ammonia and Nitrite (NO2) should both be zero ppm (parts per million). Nitrate (NO3) should be lower than 25 ppm ideally. Chlorine levels must be zero and your pH should closely match the fishes natural environment. For most community tanks a pH of 7 is ideal as this is neither acid or alkaline and so provides a balance for different species.
  4. Add decoration to your tank. It is important that new fish feel safe and have somewhere to hide. Adding new ornaments may also reduce territorial behaviours in fish that are already in the tank.
  5. If you already have fish in the tank, feed them before you set off to buy new inhabitants. Lets face it, who wants to quarrel on a full stomach? When you and your new pet return, the tank will most likely be in a peaceful state.

At the fish store

  • Always feel free to ask questions before you buy your fish. We want you to enjoy your new pets without worrying
  • Look closely at the tank the fish are kept in. There should be no uneaten food and any dead fish in the tank is not a good sign. How are the fish in the tank behaving? they should look bright and reactive not huddled in a corner looking stressed.
  • If you would like a particular fish from a tank, feel free to ask the assistant to catch it for you. So long as it isn’t a tetra from a shoal of a thousand, they should be happy to accommodate. Bare in mind that it is not always possible to sex fish reliably depending on species and size.
  • Ask what food the fish have been feeding on and the time they are used to being fed. This will help to maintain routine which will further reduce stress.
  • Purchase a stress reducing formula. These water additives are designed to relax fish and provide additional protection against illness.

Now that you have chosen your new pet, take it straight home. If you need to make any other stops, please do so before you go to the fish store. The less time your fish spends in the bag, the better.


What to do when you get home?

  • Turn off the lights in your aquarium. Fishes eyes take much longer to adjust to changing light levels than ours. Being removed from a dark bag only to be placed under a bright light is going to be a shock. Add the stress reducing formula.
  • Place the tied bag containing your fish so that it is floating on the surface of your aquarium water.
  • Allow the bag to float for fifteen to twenty minutes and the cut the knot off the bag and roll down to form a “collar” that will keep the bag afloat.


  • Take a cup of water from the aquarium and pour a little into the floating bag. Take care not to put too much in at once as this will cause the bag to sink.
  • Repeat this step every few minutes for the next quarter of an hour. This allows the water in the bag and your aquarium water to mix so that any changes to pH or other parameters happen gradually.
  • Tip the bag gently to allow your fish to swim out in their own time and explore their new surroundings.

  • Lastly, spend some time observing your new inhabitant. Keep an eye open for other fish bullying him or her. If this does occur, add a small amount of food as a distraction. and monitor.
  • Leave the lights off for a few hours to allow the new tank mates to adjust. Most fish are naturally more docile at night.

Relax and enjoy your new pet…

For the first few days, keep an extra close eye on the tank just to make sure everybody is getting along and getting a chance to feed. If you have followed the steps above, introducing a new fish shouldn’t be a stressful procedure for anyone.

If you have any questions, please feel free to e-mail us at

Thank you on behalf of us and your new fish for taking the time to read this article.

Introducing Your New Fish To The Aquarium PDF Download


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