Here’s my two cents, going on my experiences with Muscovy drakes:
I currently have five drakes. Two are new and have just settled in. They’re smaller than my established three, so they haven’t challenged the three. And I have 28 females. That’s about nine ducks per drake, not counting the two newbies. I’ve heard that Muscovies do best with about ten ducks per drake. That seems to work fine, although they do okay with more drakes per duck too. The three older drakes usually get along great. They nap next to each other, talk together, investigate the girls’ nests together, etc. About once a month, two of them will have a big fight, and after that everything’s fine and dandy again. Young drakes always get into fights no matter what as they try to figure out who’s boss and who’s not, but after a few weeks they’re fine.
I do separate them for the night, though. They have plenty of space when they’re free-range, during the day, but their two night pens are considerably smaller, so I put the top and bottom drake (who never fight with each other) in one pen and the middle drake and two new drakes in the other.
I’ve only had one that became aggressive. We got him when he was a few weeks old and handfed him a lot, so he became extremely unafraid of us. He started showing signs of aggression when he was about one year old, challenging us and pecking. Nothing we did really convinced him once and for all that we were boss, but today he’s fine. He’s over three years old now. Occasionally he’ll still challenge me, but I never let it get farther than that. I usually pin him down until he walks away when I “peck” him.
After him, I tried not to let any drake we were planning to keep become too tame. And none of the others have become aggressive.
I’ve never had issues with drakes hurting females or each other. When there’s a lot of young males just becoming mature (which is around four months of age, and is when they gain their hiss, start trying to fight and mate, and start developing caruncles), their sisters often lack a lot of feathers around their neck where the boys grab them, but they’ve otherwise been fine.
I feed them the same thing I feed the females—chicken layer mash and some milo (sorghum). They eat less than the females. They would probably do fine on just plain milo (or oats, corn, or wheat), though, except maybe when they molt and need more protein. My ducks do find a lot of their food from foraging.
A lot of people say Muscovy drakes have a major tendency to be aggressive and rough on girls. I find mine to be, overall, very peaceful, and once they’re older and not so hormone-crazed, they mostly just casually talk with other drakes or follow the girls around and keep an eye out for danger.
Here's a few pics. Captain, the oldest drake, just before his molt:
A young drake, four months old:
And King, who's two years old:
