I believe Bob recommended, but we all know how my memory is:
U. nelumbifolia ~ boggy sand & peat, just like I have it.
U. reniformis ~ fluffy live LFS type dilly.
I didn't know their preferred media at first when I stuck them into this mini bog. But by the time I had a direction on their growing conditions, they had already broken the surface with new growth. So I said screw it and left em'. They seem happy enough..