Distressed Goldfish

Early this morning one of our fantail goldfish was entangled in some string
algae. When I fished him out of the pond, I thought he was dead until he
twitched a little in the net. I put him back in the pond and tried to push him
around a little to get water to flow through his gills, but he wasn't really
responding. The water was really cold (38 degrees) so I thought maybe it was
too cold for the fish to resuscitate, as cold water doesn't store as much
dissolved oxygen as warm water, and I figured the fish was exhausted from trying
to free himself from the string algae and needed oxygen. I filled a large
container with water from the pond, put the fish in the water, and brought him
inside. There I pushed him around some more and blew air into the water to get
some more dissolved oxygen into the water. I also fed him a little.
He seems to be doing fine now. But now my question his: should I put him
back in the pond, after acclimating for several hours, or get an aquarium for
him until the spring? The fish is going to have gone from 38 degrees to
something like 68 degrees and back in a little more than a day, and I'm thinking
that may be too much stress for the little guy.
Opinions are more than welcome. Thanks.