I have found the best way to set up emersed tanks for me personally is to divide the tank with a piece of glass or acrylic so theres a water area, you don't need to seal the divider or anything. On the land side I put down about 1.5-2'' of hydroleca clay balls then regular potting soil or whatever's lying around on top. In the water section as I don't want any animals I put pots full of hydroleca and use them for Spathiphyllum, Anubias, Microsorum and various mosses. Works a treat.