I was reading one of the care calendars put out by one of the German Bonsai forums, and they mentioned using a bit of kanuma in the soil Mix for Japanese maples. Do any of you have experience with that? My maples both did fine last year with a normal Mix, but repotting season is coming, and I want to at least consider why they might have written that. If it is a good idea, I will have to buy more kanuma.

Kanuma is used mostly for acid loving plants. Kanuma facilitates fine hair root growth. It retains moisture and can absorb more water than it's weight and yet allows for air space. It's PH varies from 4.5 to 5.

I can recommend Fuji sand (Black lava) for Maples. Fuji sand is a Lava granulate used in soil mix and can be mixed with any type of soil, particularly suitable to Maple, where the leaves get a really nice autumm color, which is due to the minerals this lava contains. Is suitable as top dressing for your bonsai tres.

I do know what kanuma is, and why it is used for azaleas,
I was just wondering if anyone had experience with what this particular Club, and forum reccomends.

Maples love Kanuma because it makes the soil more acid and will give the tree great results. It will grow quicker and healthier.
Put 10-15 procent Kanuma in your maple soil mix.
Use Fuji sand as top dressing for your Maples.
Thats my recommendations.