Help! Fighting ducklings

[muscovymama72]

I have an 3 week old duckling, Indie, that hatched after the mother duck left with all the ducklings and never came back. We ordered her 2 more duckling so she wouldn't be alone and we are having a hard time introducing them. They are 4 days old and one of them is very aggressive toward Indie. Indie doesn't like the angry duckling either and is okay with the other one and just ignores her. When ever they are out together the two try to fight. They have separate brooders in the same room so they can hear each other, just not touch. Any ideas on how I can stop the aggression and have them be friends?

 

[Sonya9]

Can you put them in the same brooder with a divider so they can see each other? I might consider putting the new newcomer in with her.