I also try to do that with my extra boy's, but these Biel boy's seem to be able to be good with each other. I do try to rehome these extra Biel boy's, at least the one's that I don't want to keep for my own breeding. Some people would like a rooster but don't want one that will be aggressive, so this breed is a good one for that. I have eaten bad boy's before when I was doing other breed's.I give away or sell as many as I can. I also have a bachelor pen and also go the knife route with the rare bad roo or ones I just can't find another option for.
I have. I use a fenced off space inside the duck pen just like I do for chickens. The only difference is the ducks integration pen doesn't need a roof and can be stepped over. Add the young ones to the fenced area and let them see but not touch for a week or two. I have one drake that always has to be removed before I let them all mingle. He gets turned loose in the garden for the first week of mingling and then added back with the others...then removed, added back over and over until he stops being aggressive. It's easier to integrate my ducks when it's not breeding season, but I've had good results for all but one timid girl that my senior girl just won't accept for some reason.
Thanks' for your duck advice in case that I have to go that route.