Methods of acclimatisation

Since I had the tests out and I also had some spare test tubes, I decided to test the water which the fish were coming from:

  • KH: 6 ° (107 ppm)
  • GH: 16 (286 ppm)
  • ammonia: 0 ppm
  • nitrite: 0 ppm
  • nitrate: 20-80 ppm
  • pH: 8.0

As can be seen from the above results, the difference between that and the aquarium water is quite significant! If I was to move the fish straight over, they would probably get quite a shock from the difference in hardness, so I would need to acclimatise them first.

My preferred method of acclimatisation is often referred to as “drip acclimatisation”. The process is simple, although time consuming:

  1. I start by gently tipping the bag with the fish and LFS water into a bucket (8-10 litres for small fish, larger for larger fish), have something ready for covering the bucket as many fish are able to jump
  2. If the fish has been in transit for any significant period of time, or you have any other reason to suspect that there is ammonia in the water, add a product which temporarily converts ammonia into ammonium
  3. Add some décor and/or plants to make the fish feel more secure and relaxed
  4. Add a heater and airstone if needed, for example, if the air temperature is cooler than the aquarium water or if the fish have been in transit for a long time
  5. Next, set up an airline with a knot tied in it so that the flow can be controlled, to drip 4-10 drops of aquarium water into the LFS water per second for a 9 litre bucket (depending on how sensitive the fish are and the difference in water parameters: the smaller the difference, the faster the flow), for larger buckets, a faster flow should be used, for example, 10-20 drops per second for a 20 litre bucket so it takes approximately the same amount of time to fill
  6. Once the bucket is full, which usually takes 3-6 hours, remove the airline
  7. Transfer the fish from the bucket, into the display aquarium using a net, trying to minimise water transfer by not even dipping the net in the aquarium
  8. Disconnect all equipment that was used
  9. Throw away the water in the bucket (I water house plants with it)
  10. Disinfect all equipment used and throw away plants which were used during acclimatisation
  11. Top up the aquarium with dechlorinated water

The more common method involves floating the bag in the aquarium for a short period of time and occasionally adding large volumes of water to it: this does not particularly help the fish become accustomed to the new water and can be as harmful as not acclimatising at all. From what I have seen, this is one of the most common reasons, after ammonia poisoning, for deaths in new fish.

2 thoughts on “Methods of acclimatisation

  1. This is a wonderful article. I have Harlequin Rasboras arriveing on Wednesday and I’ve been worried about the diffrence of PH . As even though I’ve been asured that the Harlequins are okay in 7.5, they are in 6.5 ph currently.

    • Hi Rebecca, I also keep harlequin rasboras. They originate from the Mae Klong river where the pH is reported to be from 6.0-6.5 to 7.5-8.0 (depending on the source), which is the expected range for “neutral water” fish such as these rasboras. As long as you take your time to acclimatise them, they should be able to adjust well between their current water and your aquarium water.
      I found that as long as the water is not too acidic, the aquarium size is actually more important than the parameters: a friend and I bought 10 each from the same group at the local fish shop on the same day. She lives practically next door to me and I helped her set up the aquarium, so water parameters, décor and even food are identical. A few weeks after this, she had to go abroad for a few months, so I ended up looking after her fish for the best past of their early life. The only difference between the two aquariums was that hers was 60 cm long, while mine was 100 cm long. After one year, my rasboras were approximately 15 mm longer.
      Good luck with your new fish!

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