Frog and toads can travel long distances over land during wet weather. Newts in the form of efts can travel long distances to colonize new bodies of water as well. Amphibians with no terrestrial life stage may find it hard to colonize a new body of water such as a pond that is fairly isolated. Species like mud puppies or waterdogs for example would be unlikely to populate an isolated pond.

I seriously doubt they would play anything but an insignificant role in the food chain of a pond. The only reason to stock them would be for personal desire and the uniqueness of having them in your pond. Most of these aquatic species do not do well in ponds where fish are present. Rather relying on vernal ponds or ponds that are too shallow that fish cannot survive in them or too isolated to be colonized by fish.