What is acclimation?

Acclimation, also called acclimatisation, is the process an organism undergoes in order to adjust to changes in environmental conditions. (Note that strictly speaking, acclimation refers to the changes an organism makes under experimental conditions and acclimatisation refers to the adjustments to natural environmental changes (Schmidt-Nielsen, 1975).)

Whenever an organism is moved from one tank to another (e.g. from the tank at the LFS to a tank at home), it is very likely that the water conditions between the two tanks will be different. The most obvious parameters will temperature, specific gravity and pH, but a great many other properties may be different including dissolved oxygen and carbon dioxide, calcium, alkalinity and the various salts such as magnesium and potassium. Additionally, the longer the organism has been in the bag, the greater the build-up carbon dioxide and other waste and this may affect other parameters.

While most organisms have fairly wide tolerance for these properties, they need time to adjust to the differences. This is why we need to provide them with a more gradual transition from one set of parameters to another.

How long should acclimation take?

Unless the water parameters are vastly different, for example a large difference in specific gravity, 30 to 60 minutes is all that is required for the majority of organisms to adjust to changes in conditions. The exception to this are the echinoderms: sea stars, brittle stars, crinoids, sea cucumbers and sea urchins. Echinoderms are generally intolerant of large changes in water properties, in particular salinity. It is necessary to take significantly longer to allow echinoderms to acclimate - up to 20 hours in some cases.

It is good practice to measure the specific gravity of the bag water once its temperature is the same as the tank water. If the specific gravity of the bag water is within 0.001 of the tank water, a normal period of 30 to 60 minutes can be used for most organisms and around 5 hours for echinoderms. If the difference is greater, more care needs to be taken, especially with echinoderms.

Ways to acclimate new organisms

If you have a sump, the easiest (for you and the organisms) way to acclimate new organisms is by placing the bag in the sump and slowly dripping water from the tank into the bag. All you need is a piece of airline tubing long enough to reach from the tank to the sump with either a plastic airline valve or clamp to control the flow of water. Figure 1 shows how this is done.

Figure 1: Sump acclimation.

Start the siphoning of the tank water directly to the sump with the valve or clamp open. This will rinse the tubing with fresh tank water and then allow you to adjust the flow down to what is appropriate. Adjust the flow to the rate of about one drop per second (or one drop per 5 seconds for echinoderms). Leave it going for around 10 minutes and see how quickly the bag is filling. Ideally, you want to add 10-20 times the original water volume in 30-60 minutes (or 5-10 hours for echinoderms). The actual flow rate required will be dependent on the amount of water originally in the bag. If you start with a low flow rate you can increase it gradually to meet the required flow rate. If the bag is not large enough to hold 10-20 times the original volume of water, you may need to discard some of the water from the bag part way through the process.

Once you have added sufficient water to the bag, discard most of the water from the bag and float the bag in the tank for a few minutes. This is to adjust the bag water to the tank water temperature which may be slightly different from the temperature of the water in the sump. Finally, release the new organism into the tank. If you have any doubts about the quality of the water in the bag, it is best to throw it away rather then letting it get into the tank. For fish, you may need to pour the water through a net into a bucket and then place the organism into the tank. For other organisms you should be able to lift them directly out of the bag and into the tank.

The benefits of sump acclimation is that it keeps the bag water at the correct temperature as well as gradually introducing the tank water. It is also requires very little effort.

An alternative to the above is to transfer the water and organism from the bag into a rigid container and place that in the sump. A rigid container is usually easier to work with and will generally allow much more water to be added.

If you don't have a sump, a similar technique is to float the bag in the tank and siphon tank water from a jug placed on top of the tank as shown in Figure 2.

Figure 2: Tank acclimation.

The procedure for tank acclimation is much the same for sump acclimation except that the water in the bag will already be at the same temperature as the tank water.

References

Schmidt-Nielsen K. 1975. Animal Physiology: Adaptation and Environment. Cambridge University Press, London. 699pp.

Last updated: April 25, 2003