Coming from a self proclaimed "fern freak" I love the idea of a full fern tank. There are quite a few that stay small. I have at least one fern in every tank I have ever built. And fwiw, 2" pots are way too small. 3" minimum is a good size. Otherwise, the roots will eventually get bound up and the plant will suffer. Unless you want to pull each plant every year, trim the roots and replant.