I'm planning on 4 ducks. The pen is just so that they can go out at night, I plan on storing their water in the pen so they'll mess up the bedding less. Mostly they will free range in our main yard, or they have a 15x30 section that is also their own.
I plan on giving them a children's pool but that will be kept outside the pen where they will be most of the rime. The pen is made of 1/4 welders wire which is also buried 12" down. On top of that I'm going to line the outside of the pen with heavy rocks so it will be even more predator safe. The roof is on but I don't have a photo yet. It is corrugated galvanized steel.
The dirts here is extremely fine and powdery. I see it becoming a quagmire very fast. I'm thinking of getting round rivers stones for the inside of their pen. I'm not sure if thats a good idea. I imagine it will be a little hard to clean. But I think a muddy pen would be worse. The rivers stones can be hosed off at least.