Common plecs are tropical fish so no, they will not survive in ponds. They will continue to grow up to about 18 inches which is why they are not recommended for any but the biggest of tanks. If you wish to re-home him, contact your LFS (perhaps the one who sold him to you without properly explaining the ramifications) and see if they will take him back.
Unfortunately there are more big plecs about than there are tanks that will hold them.