That is a bit off on the ratio, I have 4 drakes and 12 duck but breaking it down 1 drake has 5 ducks that's my oldest ones 6-9yrs old then my next drake has 3 ducks they are 2 yrs old then my 1 yr old drake has 2 ducks and my 14 week old drake has 2 ducks and they know who belong to who. And when mating is at it craziest then some of those girls mate with the other drakes. All but my oldest group they stay to themselves. Looks like you have plenty of room with such a nice pond, so why not just get more girls. Very nice duck shack.. look forward to seeing their winter one. The best ratio is 3-5 ducks per drake but it can work with less if there is plenty of room so everyone can keep a wide berth from each other. beautiful ducks too what a nice Wedding gift.