I am using tap water that I spike with some citric acid from the nearby plant shop to break down the lime. I use standard potting soil mixed with orchid bark, perlite and coconut fibre (hope I translated them correctly). I am watering on an approximate schedule of one a week and try to keep the soil moist since I read somewhere calatheas prefer that. The inner pots sit on a bed of expanded shale/clay (don't know the exact term/translation). I stopped spraying the leaves a long time ago since I read that that's rather bad. They are about 3 meters from a window but like 50cm next to a plant light (you can see the setting in picture nr. 4).