Most Bromeliads, except for a few terrestrials, are either epiphytic or semi-epiphytic and can be tree mounted or potted. A Cymbidium orchid mix is most commonly recommended but they seem to do well in any medium provided it is very open and drains well. Pine barks are the basis for most mixes. The terrestrials (especially Cryptanthus) prefer a heavier mix e.g. a fern type mix, which will remain moist. Most Tillandsias need to be mounted on wood, rock, etc. but there are a few varieties that will do better if potted in a free draining open mix.