So I am going to build a 12' long x 7' wide x 6' tall enclosure for about three muscovies. Is this enough room? The enclosure is being built around a tree (dalbergia sissoo, is it safe?) . Also what kind of floor do they need? I wanted to put a small pond, but it might just end up being a kids swimming pool filled with water. Should the rest of the floor be sand or dirt? I have grass there right now but I dont think it will stay there long with the ducks there.