How to acclimatise koi to a new environment
It is crucial to acclimatise a koi to the water if you are returning or introducing it to your pond. You may have purchased a new fish, removed a fish temporarily for treatment, taken a fish to a show or built a new pond. In all cases, your koi should be acclimatised to the water.
The Importance of Temperature
Sudden temperature changes will impact your koi's metabolism and could even kill the fish. Equalising the water temperature between the bag water and the pond is the most important aspect of acclimatisation. Koi can withstand a temperature difference of no more than 20°F. It may be necessary to adjust the temperature of your pond water to ensure that it isn't at too greater variance from the bag water. Koi cope with adjusting to warmer temperatures easier than adjusting to colder ones.
The pond into which you wish to introduce your koi should benefit from excellent water quality. The first thing you must do is ensure that your water is pristine. If it isn't, you might have to delay introducing a fish until you have resolved any issues.
Float the bag containing the fish in your pond for roughly 30 minutes. Float it for longer if the difference in temperature is greater than 10°F. Then, scoop the koi out of the bag and into the pond with your hands. Discard the bag water and don't empty into the pond as it will contain fish waste and the water will have an unstable pH level. Cover the pond or tank with a net as koi can become jumpy when they find themselves in a new environment.
The next step is to place pieces of polystyrene over the net to provide hiding places for the fish whilst it is getting used to its new home.
Monitor the fish closely over the next few hours in case any issues arise.
The Traditional Method of Acclimatisation
The traditional way to introduce and acclimatise a koi was to float the bag for a while and then to open it up and add pond water to it. This process was repeated until the bag would barely float and then the koi was released. But it is now thought that it is more beneficial to get the koi out of the bag as quickly as possible, prioritising releasing it over equalising all of the water parameters. A change in pH levels is thought to be less dangerous than leaving a fish in bag water which is high in ammonia.
Every koi keeper will refine their own technique for acclimatising their fish and will discover what works best for their stock. Outcomes may vary from one specimen to another and so it is important to monitor your fish closely throughout the process. You might find that you have a sensitive soul in your pond that requires special treatment!
If in doubt, seek help from an experienced keeper who can visit your home to lend a hand.