Q: Are cultural requirements different for charcoal than for fiber and bark?
A: You can grow epiphytic orchids in any medium except soil as long as you can adjust your watering and fertilizer practices to the new medium. Water any medium thoroughly and then not again until the medium is dry. The difference in the media you mention would be in fertilization. Charcoal, tree fern or coconut fiber are usually fertilized with a 1-1-1 ratio fertilizer whereas a 3-1-1 ratio is used for bark.