When you're confident that your new koi are healthy after a three-week quarantine, you can finally introduce them to their aquatic castle, whether it's an aquarium or pond. Koi can go directly from quarantine tub to pond if the pH values and temperatures are close (0.2 range for pH, and a 5 degree Fahrenheit difference for temperature).
If you're using an outside pond, keep in mind that the water must be 70 degrees F or higher. Adding a new fish to a too-cold pond shuts down the fish's immune system exactly when he needs it the most. If the water isn't warm enough, leave your koi in its quarantine tub until warmer weather arrives.
The pond temperature is likely to be different from your quarantine tub's temperature. Take a few precautions to avoid stressing your fish:
1. Turn off the heater in the quarantine tub and let the tub reach room temperature overnight.
You want less than a 10-degree difference between pond and tub temperatures so your fish aren't shocked.
2. The next morning, if the tub and pond temperatures are more than 5 degrees apart, you need to bag and float your koi in the pond.
• Use your koi net to bowl your koi (take the handle extension off your net if you're inside).
• Pour the bowl into a waiting and partially submerged poly bag or lift your koi into the bag. You want just enough water in the bag to cover the fish so the bag isn't too heavy. Rubber-band the bag closed and lift the bag out of the tub.
3. Carry the bag to your aquarium or pond, ease it into the water, and let it float for 20 minutes to equalize the temperatures.
Keep an eye on the bag(s). Don't let them heat up in the sun.
4. Open the bag, lift out your koi, and release it.