Goldfish and koi must we warmed up slowly before adding them to your existing water.
The first option you can try is to leave the box of fish sitting on the floor for a period of time before floating the bag on your aquarium or pond.
Your second option is to float the bag in the aquarium or pond water until the temperatures are closer. Sometimes goldfish and koi may look lifeless or dormant. As they warm up goldfish and koi generally come back to life in perfect condition.
If you panic and add the goldfish and koi to the water too soon, the stress level in your fish will increase significantly, causing health issues or death. By using one of the methods listed above, you are sure to have healthy fish swimming in your aquarium or pond.
Whichever method you choose to use to acclimate your goldfish and koi, the number one rule to follow to insure you get healthy fish into your tank or pond is to keep the stress level for the goldfish and koi to a minimum.