I did the gradual transfer, but it was late so I only did it quickly over only 45 minutes. I am hopeful that going from warmer to colder water was less harmful than the opposite. I have more concern about pH and alkalinity. I will report back when I know more. For me, it is worth the risk of failure. I think cold introduction might be less stressful than during the warm season. The pond is completely open now that things warmed up a bit. Your comments give me greater hope that these are PK shrimp. I really love this stuff!