Many Japanese use Akadama and Pumice based potting mixes, they also use lots of other combinations, depending on where they live and what they are growing. Some plant in 100% akadama, various kinds of river "sands", Kiriyu for one, which are more like a finer pea gravel. The key attributes are associated with water retention, oxygenation and inorganic.
If you know exactly what the water requirements for your trees are, and based on how you water, for example hand watering vs automated water, frequency of watering and developmental state of the trees. See Peter Tea's piece on soil and repotting on his blog..
