I had a smaller pond than yours on my previous property for 30 years and I found that early in the spring there would be a period of murkiness and sort of an algae rise--stuff that had been happily on the bottom of the pond through the cold months would float up and look, well, pretty disgusting. And then, all on its own, the pond would clear itself. In fact, what I learned about my pond was this: the less than I did, and the more that Mother Nature did, the healthier the pond was, meaning that the fish and frogs and plants did *much* better after I disconnected the filter we had in the beginning and did nothing further than run a very small aerator in the winter to keep just a small area clear of ice so the over-wintering animals would not suffocate under the ice.
Now, your pond is larger, and yet I would imagine it will be much the same. Expect a period of general yuckiness early in the spring. Add plant material that will grown underwater to help aerate--plants breath in CO2 and breath out oxygen. (There are lots of great online pond resources including the oldest US pond specialist, www.Tricker.com)
There are also several types of mollusks that aerate--snails and such--and they could be added as well. And once things seem to be okay, then take your hands off it and allow nature to do what nature does best: live!
I moved in the fall to a larger house on a smaller lot and miss my pond soooooo much! We are hoping to add one next year. This summer, I will really miss falling asleep to the frogs in my pond croaking--a few optimistic males looking for a few willing females.
Love your pond, it's filled with life!