Guide for introducing new fish into your aquarium

  1. Before bringing them home, test water quality of aquarium and adjust if required. Also be sure that the new fish are compatible with the current population and that they will not overcrowd the aquarium.

  2. Switch off aquarium lighting.

  3. Float the unopened fish bags in the aquarium water. You can do this at the top of the aquarium or in a container of water that has been removed from the aquarium, such as a bucket). A separate container can be helpful, especially if you have a large number of fish to introduce or they are spread out in many bags. If you are introducing a large fish, it is often easier to put it into a tub or bucket on the floor first.*

  4. Use the opportunity to inspect the fish carefully for stress, injury and any sign of disease or other problems. If the fishes look distressed (losing orientation, rapid breathing at the surface etc), release them into aquarium water ASAP, preferably into a separate container. After 5 minutes, open the bags and add a little water from the aquarium to them. A third to half of the original volume is a good rule of thumb.

  5. Keep the bags floating open. An easy way to do this is to roll the edges down, trapping some air in the rolls. If required, secure the bags to the edge of the aquarium with a peg or similar to stop them drifting around or tipping in the current. Watch out for fish jumping from the bags – it may be necessary to loosely retie the bags with a rubber band or a peg.

  6. Every 3-5 minutes, add a little more water to the bags until you have doubled or tripled the original volume.

  7. Pour the fish and water into a soft net over a separate container. Quickly release the fish in the aquarium. Take care that they don’t jump out of the net – a hand over the opening can prevent accidents.

  8. Discard the water in the tub.

  9. Close the lids on the aquarium.

  10. It is a good idea to leave the aquarium lights off for half an hour to let the newly introduced fish settle in.

  11. Check on the introduced fish regularly for the next few days.


 * If you are using a tub or bucket, the principles above apply with some modification. Release the fishes into the tub, ensuring that there is at least enough water to cover them completely.

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