I've been given some young koi by AZKalEl (Thanks, by the way), and
have a question about transfering them to the main pond. Currently
the koi are living in a tank where the water is about 72 degrees.
After keeping them in isolation for another couple of weeks, I'd like
to transfer them into the main pond, which currently is at 60 degrees.

Does anyone have any recommendations on doing this? I know rapid
temperature changes are bad; and I seem to remember reading that cold
to warm changes are less of a problem (but could have it backwards)
Obviously heating the pond is not possible (unless I just wait until
it warms up to 72 degrees), but I don't have any good ideas about
cooling down their present home slowly. Cooling down the house to 60
is also not an option.

PlainBill
He that would make his own liberty secure must guard even his enemy from oppression, for if he violates this duty, he establishes a precedent that will reach to himself.
-Thomas Paine