a couple newbie questions for a first viv

[edibug1]

I have everything I need for my first vivarium, and the only thing I need is a peice of screen to seperate hydro balls from soil. I want to be able to plant the tank, but I dont want the substrate to be a half foot high, so I need something that will seperate the two layers, but allow plant roots to creep into the hydro balls, so if someone could give me a specific material(mesh, misquito screening, ect.), that would be cool. Also, for some small ferns and broms, how thick will my layer of soil have to be? Thanks!

[beckdg]

the soil layer only has to be a couple inches. fiberglass replacement screen from any store with a hardware section makes a good divider.

[froggsong]

Also, broms generally do best mounted than planted in the substrate,