On a side note, how study is the cardboard you are using to keep your ducks in? My experience with cardboard and ducks is not good. If they splash enough water to get the cardboard wet I'd be worried about it collapsing. And I've heard of ducks eating wet cardboard before. Just be sure to be careful, don't want your brooder to cave in endangering your little ones and possibly bringing down a heat lamp with it.
Oh and .
I'm new here too but that doesn't mean I can't bid others welcome.