I always read that trio's are better. What 'if' something were to happen to one of them? Then trying to find another the same breed and age is not easy. If you have that source available than I guess you could get by with pairs. If not, trios. I love our ducks, have fun.
As henry said what if something happened to one of them it would be hard to get another same age etc especially the female.
This was my main reason for asking as i was thinking of one been without a partner.
As the pair i have now are very close, and i would feel sorry for one to be without a back up partner as such should anything happen.
The paradise are 120euro a pair, so i think i will stick wit a pair for them.