Blueberry Family Substrate

I wanted to start a discussion on what kind of substrates are recommended for the vaccinium family of plants. I am currently growing several different vaccinium species, including Red Huckleberry, and native High Bush Blueberry, and have noticed extremely fine roots in clusters similar to azalea; this leads me to believe kanuma may be a good option, does anyone else have any good ideas?

I use the same substrate that I use for my deciduous trees - 3 or 4 akadama, 1 pumice, and 1 lava. They are prebonsai and are doing well as long as I remember to adjust my water pH from 8 to between 6 & 7. I imagine that kanuma would work very well for them as well.