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How to acclimate new aquarium fish

If you are buying new fish or shrimp, they may be accustomed to water parameters that are very different from yours, and therefore you may want to slowly acclimate or get them used to your aquarium water. If the animals are small enough, you can acclimate them in a specimen container or bucket.

  1. Cut open the fish bag and pour the animals and some of the water from the bag into the catch cup so the fish are completely covered in water.
  2. Add aquarium water from their new home into the catch cup so that the water level is doubled. (If the water gets too high, just pour some out of the container.)
  3. After 15 minutes, add more aquarium water so the water is doubled again.
  4. After 10 minutes, add more aquarium water so the water is doubled again.
  5. Net the fish out of the container and add them to the aquarium.

For an even more gradual acclimation process, look up how to do “drip acclimation” using a length of airline tubing. If the fish are frantically dashing around in the catch cup, you can calm them down by darkening the room and/or covering the container with a towel.

If you purchased the fish online and they were shipped to you, you may want to use the "plop and drop" method instead. The reason is because ammonia and carbon dioxide from the fish's waste and respiration may have built up in the bag, causing the pH to drop. When the fish bag is opened, the carbon dioxide is released and the pH rapidly rises, causing the ammonia to become toxic and burn your fish's gills. To prevent this from happening, allow the fish bag to float in the aquarium for 10–15 minutes to acclimate them to the water temperature.  (If the fish are in a breather bag that allows gas exchange, place the bag on the aquarium lid for about 30–60 minutes.) Place a fish net over a bucket, cut open the bag, and pour out all the water in the bag. Gently lower the net into the aquarium and let the fish swim out on their own. Any fish that have passed away will remain in the net for you to easily remove.

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