I really appreciate everyone's feedback and advise on this. I am still new to the forum here, and still quite new to ducks and chicks, so it is really great that people here are so nice about sharing info and advise.
It has been a few days now. The ducks still aren't figuring out their pecking order, but we are trying to wait it out a little longer to see it the situation sorts itself out, and if not, the new ducks will have to go back with the rest of their flock (living at a friends house).
Dh wouldn't hear of doing anything about the "mean black one" causing the problem because "he was here first". And I really don't want to get rid of "the twins" because they are so darn cute and comical. They do EVERYTHING at the same time (turn their heads, lift their foot, preen their feathers, etc), and it is the funniest thing I have ever seen (guess I don't have much of a life- huh? lol ).
As far as their area, they have a nice size outdoor area with a small 7x7 pond. I wouldn't say the area is large, but I think there is plenty of room for the others to get away (it is maybe 30x30 and is shared with the chicks as well). This area was slated to expansion next spring, but we may need to do it this fall and add more secure wire.
The "house" is definately too small. It was fine for the chicks and the 3 ducks, but I feel the confined area will create a problem with the new ducks not being able to get away from the agressor.
I want to start expanding that now, but dh again tells me to wait. I don't see the situation for night time working out without the expansion. And the weather here in NY isn't going to work with leaving them outdoors much longer.
The other ducks and chicks have always been locked in their house at night and are free to come and go from the house in the day.
The new ducks are very unhappy about being left outside and really want to be inside with the others. They quack at the door of the duck/chick house for 30 min to an hour when I lock the others in the house at night.
They get along fine with the Rouen (who snuggles with them when they nap) and the Pekin (who they follow around like it is their mother).
Also, I have noticed now that the Rouen and the Pekin almost seem to try to get inbetween the new ones and the Swede when there is an issue.
So far, no blood, and not many lost feathers- just lots of grabbing and some feather "tugging". I have noticed that the Swede's neck shakes and quivers when he is being agressive (not sure if this means anything or not, but wanted to mention it in case).
I am just not sure they will live in harmony enough to be in the house together at this point, and not sure how many days to give the situation. Though it did take a couple of weeks for the ducks to adjust to the chicks without lunging at them.
Why can't everyone just get along???