If you gradually introduce the fish into the pond water you should be fine transferring them into a pond. After all where do pet store fish for the pond come from when you buy them, a tank of course.  Every Winter I bring in my favorite fish inside to a 140 gallon tanks with tons of filtration and they go back to the pond in the Spring. You should wacth the tank fish carefully for stress and provide them cover from the other fish ( plants, large rocks, plant stands, overturned pots) where they can hide.  When you go to transfer them mix the water from the pond in with water from the tank gradually. I would suggest using a Large rubbermaid and mix 50% tank and pond water for at least 30 minutes. Then gently dip them out using a large bowl or net.

Let us know how it goes, Gail

Gail Hopkins

Http://www.richdeer3pondsupplies.com
richdeer3@...