I'm interested in your experience with top dressings. I've read about how moss can be difficult in our climate and solutions for making it work in the Parameters for growing moss chat. I don't think I'm ready to mess with that, yet. Still, I am having issues with soil washing away when I water – particularly on store-bought, deciduous trees that have more of a traditional soil, instead of the akadama mix I've used on others. So, I'm looking for ways to cut that out. I have one tree from The Bonsai Nursery with a kind of sharp, small, black rock on top. I can't tell if it's lava or not, but it seems to work really well without the bulk of chunkier lava I've seen around. Perhaps the solution is going back and asking what they use, but I'd still like to know more. What do you use?