I would also wait till april/may time to add them
My grandad has got pearlscales in his pond that were from one of the other grandchildrens tanks and they have done well 7 were added and only 2 died which is good for a non hardy fish
These were added to the pond 2 years ago and the remaining 5 are still alive and have been breeding - there are blackmoors , orandas , pearlscales , Koi carp , comets , shubunkins and o bugger forgot the name of the other ones , all the fancy ones have been added from familys tanks in april to may sort of time and most have weathered well over freezing winters
Good luck
Sarah xx