Wow, that's a big pond and a big project! I wouldn't know where to start!
The peacock of course doesn't really use the pond or does he? I don't know if they can swim!
Ducks will eat both pond fish and plants and produce a lot of waste. That said, I love ducks and have always wanted some. It sounds like your pond is big enough to accomidate both them and other pond life.
There are so many kinds of fish, plants, tadpoles, snails, waterfowl, and turtles that you could add! Because the pond is spring fed, I assume it also has a stream draining from the pond. For this reason, you should try to stick to native species to avoid any flowing down stream.
I'm not sure where to start either so could you ask some more specific questions?
My page on big ponds like yours is at
http://www.fishpondinfo.com/farm.htmMy native fish page is at
http://www.fishpondinfo.com/misc2.htmI also have pages on everything else pond-related.
With a pond that big, you probably don't know all that is down there as far as fish and turtles go as there may already be some in there. I wouldn't be surprised if some catfish and snapping turtles lurked the bottom.