I have five ducks currently, and I think I'm going to re-home two of them due to my drake constantly bullying them. So if I'm down to two ducks, how big of a natural pond would they need? I know bigger is better, but since I moved in with my dad they've been in the pond out back that we've had for years. It's not huge, but it's a decent size. I'll have to measure to know for sure. It is mostly fed by rain, but doesn't really drain anywhere except when it overflows. My dad's getting upset because the water is dirty and the ducks are eating everything, despite being fed regularly. Anyway, I just want to know how big a pond has to be in order to use plants as a sort of filtering system, and if it would be enough on it's own.