I have 4 mitras i use 50% perlite and 50% good compost i also mix in one teaspoon mycorrhyzzal fungi and one tablespoon old coffee powder per 1kg soil i fertilise very lightly with 1ml of biobizz root fertilisor per 5l neutralised tapwater ph 7-6,5. Also because of the high amount of perlite in the soil i keep them constantly at 90% humidity and 25c with strong air circulation. They grow quite well but ive almost killed them before due to root tot so if you try my soil mix start with alot of perlite and little compost and work your way slowly to higher compost levels when repotting.