Acclimatising New Corals And Fish The Correct Way

The purpose of acclimatisation is simple – the water that the animal is packaged in may have a different temperature, pH and salinity than that of your aquarium. Aquatic life (especially corals and invertebrates) are very sensitive to minor changes in water parameters therefore acclimatisation is a requirement for success.

There are two ways which are recommended to acclimatise your new purchase to your aquarium. Neither of these should be rushed and should both be performed with the aquarium lights off. The lights should also remain off for a further 6 to 12 hours after the animal has been introduced to the quarantine tank, or the main display tank, whichever you are using.

Floating Bag Method

Before you commence ensure that the lights on your aquarium are turned off. Also ensure that the lights in the room where you will be unpacking the animal are turned down to a minimum. Bright lights will cause excessive stress to the animal.

  • Float the bag whilst it is still sealed in the aquarium for a minimum of 15 minutes. Do not open the bag at this stage. This allows the water in the bag to slowly adjust to the temperature of your aquarium.
  • Once a minimum of 15 minutes has passed open the bag as near to the top as possible and either attach this to the side of the aquarium, or create an air pocket in the top of the bag so that the bag will float.
  • Once the bag is open add half an egg cup of your aquarium water to the bag and wait 5 – 10 minutes.
  • After 5 – 10 minutes again add half an egg cup of your aquarium water to the bag and wait another 5 – 10 minutes.
  • Continue with this process until the bag is full.
  • Once the bag is full remove the bag from the water and discard at least half of the water from the bag.
  • Re-float the bag in the water and repeat the steps of adding half an egg cup of your aquarium water to the bag again until the bag is full (Remember to wait 5 – 10 minutes between each water addition)
  • Once the bag is full capture the fish using a proper aquatic net and release into the aquarium. Corals can be removed from the bag and placed in the aquarium. When some corals are touched they could produce a great deal of slime – this is nothing to worry about and is perfectly normal. However do not introduce any of the water into the aquarium. Invertebrates need to be released into the aquarium under the water.
  • You should never allow them to be out of the water in air. To release invertebrates lower the bag into the aquarium and tease the animal out of the bag. Some of the water will escape into the aquarium, however attempt to keep this to a minimum.
  • Discard the water in the shipping bag – never introduce the water from the shipping bag into your aquarium.

Leave the aquarium lights off for at least 6 – 12 hours after the introduction to allow your new purchases to become acclimatised to their new home.

Drip Method

The drip method of acclimatisation is normally used for more sensitive inhabitants, however more and more fish keepers are using this method for all livestock.

Before you commence with this method ensure that the lights on your aquarium are turned off. Also ensure that the lights in the room where you will be unpacking the fish are also turned down to a minimum. Bright lights will cause excessive stress to the fish.

  • Float the bag whilst it is still sealed in the aquarium for a minimum of 15 minutes. Do not open the bag at this stage. This allows the water in the bag to slowly adjust to the temperature of your aquarium.
  • Remove the bag from the aquarium and very carefully empty the contents of the bag into a marine safe receptacle (do not use too big a receptacle). Ensure that the animal is fully submerged. If the animal is an invertebrate do not allow it to come into contact with the air – they must remain submerged at all times.
  • You will need to use some airline so that you can set up a drip line from your main aquarium to the receptacle.
  • In your aquarium secure the airline tubing so that it cannot fall out. On the other end (the end which is in the receptacle) add an airline control valve (this will allow you to regulate the flow of water).
  • With the tubing in your aquarium submerged and the other end in the bucket start the siphon by gently sucking on the airline tube. This will start the siphon and water will start to pass from your main aquarium to the bucket. As soon as water begins to flow adjust the valve so that you are getting between 2 to 5 drops per second.
  • Now wait until the water in the receptacle doubles the initial amount, pause the siphon using the control valve, discard half of the water from the receptacle and start the siphon again using the control valve.
  • Wait until the water doubles again and then stop or break the siphon. You are now ready to introduce your animal to the aquarium.
  • If the animal is a fish then capture the fish using a proper aquatic net and release into the aquarium.
  • If the animal is a coral then you can simply lift it out of the receptacle and place it into the aquarium.
  • If the animal is an invertebrate then you will need to capture it under water and keep it under water until it is introduced into the aquarium. Try to retain as little as possible of the receptacle water when doing the transfer.
  • Discard the water from the receptacle – never introduce the water into your aquarium (apart from that necessary for invertebrates).
  • Leave the aquarium lights off for at least 6 – 12 hours after the introduction.

Remember that it is very important to be patient. The acclimatisation period should take as long as needed.


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