How different are the parameters and temperature between the pond and the tank?
Depending on how different they are, the amount of time to acclimate them to the pond water will vary. Place them in 3/4ths full bucket of tank water and set it near the pond. Have something such as a screen or net to cover the bucket to prevent jumping. Add a cup of pond water every 15-30mins (once again, depends on the differences) until the bucket is full. Then remove half the water and start all over again. I would empty and refill at least 2 more times.
It typically takes me three to four hours to acclimate my guys inside for the winter to the outside pond and this is with the pond temperature being within a 5 degree range of their indoor temperature. Bringing them inside is a bit different as they will be going from the pond water and very low temps to 70 +/- degree tap water. This process usually takes 24-48hrs. Hope this helps!
