Healpful Tips

Introducing Fish Into an Aquarium


Most marine fish and invertebrates are collected in the wild; go in-and-out of multiple holding tanks and bags, this all puts a tremendous amount of stress on them, before they arrive in our hands. The species you see in our aquarium display have gone through a proper acclimatisation before they are put on sale. However, with a little care at your end to minimise any stress before introducing them into your aquarium will also help their overall health and well-being.

It is advisable to introduce new fish, a couple at a time and gradually build up your stocking level over a period of 8 to 12 weeks. It is also important to acclimatise the newly purchased fish and invertebrates to your aquarium water before releasing them into your aquarium; this will help to reduce the stress level that these fish might have gone through during packing and transportation from the aquarium shop to your home. The procedure for acclimatisation itself is fairly simple, although it requires a little patience, and does vary slightly for more sensitive species such as crabs, and shrimps that will take a little longer to acclimatise than hardier fish and invertebrates.

The following water parameters must be stable during acclimatisation:

Water Temperature

The water temperature inside the fish bag, by the time you arrive home will undoubtedly be different than the water temperature inside your aquarium. Proper acclimatisation helps to equalize the different water temperatures and can significantly reduce the stress on your new specimens.

Salinity/Specific Gravity

It is also likely the water inside the fish bag has different salinity/specific gravity than the water inside your aquarium. Beware, sudden changes in salinity can shock fish and inverts and may leave them more susceptible to infection and/or disease.

Ammonia and pH

The natural metabolic process of fish and corals releases toxic ammonia and carbon dioxide in the transportation bag, in turn lowering the pH of the water.  If the pH were suddenly raised, the ammonium would release ammonia harmful to livestock. Proper acclimatisation will raise the pH gradually, safely releasing and removing ammonia.

Of course, acclimatisation is just another item that you can do to make the transition easier, bearing in mind, if you take the time to do the acclimatisation properly; you are more likely to be rewarded with a happier and healthier species of fish and/or invertebrates in your aquarium.

The simple floating method for acclimatisation is a good method for most fish and invertebrates, with the following steps:

  1. Switch off the aquarium lighting system, and dim the lights in the room.
  2. Float the bags without opening them in the aquarium for 30 minutes to allow the temperature to equilibrate without opening the bags.
  3. After floating the bags for 30 minutes, slowly open the bag and roll the sides down, you will need clothing clips to anchor the bags against the edge of the aquarium.
  4. For the next 15 minutes, add half a cup of aquarium water every 5 minutes to the shipping bag, wait another 5 minutes and then discard approximately half of the water from the bag into the drainage.
  5. Repeat step 4 above one more time, while making sure to keep water from the bag from spilling over into the aquarium. This allows the fish and/or invertebrates to acclimatise to the water conditions in your aquarium. 
  6.  Remove the specimens from the bag and place them into the aquarium using a soft net, or for other more sensitive specimens, capture them with a cup, pouring as little of the bag's water into your aquarium as possible.
  7. For sessile invertebrates, such as corals or anemones, you may remove them by hand, making sure to use clean and sterile gloves.
  8. Discard the remaining water in the bags.


Floating transportation bags in the aquarium
Floating transportation bags
Adding aquarium water to transportation bag
Fish acclimation