ducklings living together?

[Dani043]

I have 3 Pekin ducklings that are about 3 weeks old now. today I got 2 Rouen ducklings that are about a week old I believe. My question is when can I put them together in their home? I have a trough for my ducks with food, water and a heat lamp. Should the new ducklings be quarantined to see if they're healthy? Are Rouen's usually really calm?
These are my Pekin ducklings

These are my new Rouens

 

[TLWR]

3 week old ducklings and 1 week old ducklings have a huge size difference. You have 2 little ones fitting in your had and the pekins are arm sized by that pic, so HUGE difference in size! Usually the bigger ones will bother the little ones. Not always, but usually. You can put a screen between them in the brooder to introduce that way and then try it, but I'd expect it not to work so well doing them together.

 

[Dani043]

The Pekins love my 8 baby hens which are about the size of the new Rouen chicks. I'm going to introduce them in a controlled environment this weekend and see how they get along I think...

 

[My chicken s]

I got six Perkins today they are so sweet

 

[My chicken s]

So I would try it