I don't see any real harm in releasing the rest of the tadpoles from the puddle into the lake, but why not return them to the puddle? The alleged bullfrog tadpoles are a different matter. I advise against releasing animals of unknown origin into the wild; they might harbor disease and could be of an alien genetic stock. Try to find out where they came from and take them back there. By the way, the correct spelling is "metamorphOsis."