It is Czech made You won´t buy it in the U.S. I guess
It is substrate that everyone on our local forums disapproves of - but I still use it even as additive to zeolite for holding the moisture (80to20).
I guess you can use just any bonsai mix that any shop sells - for few months that air layering would be on it should be ok.
If you do the cuts properly you should have no problem with branches to root.
I lost 2 branches so far this year but it was my fault - I had cut in too deep.

simplysaid wrote: lso read that Sphagnum moss can have fungals that can hurt the tree.

Spaghnum is actually a substrate that limits a lot of diseases, notably fungi, from growing.

cool

2 more pics - 1 by sunset and the other after trimming the top growth to promote backbudding lower on the trunk

Looks great kristof!
You've definitely gained great experience. Regardless of your non bonsai empire certified substrate.

Ficuses grew nicely indoors, even over the radiator on the window sill (quite large one that is).
I didn´t cut anything at all, preparing me some branches for grafting as backbudding on lower trunk never happened.



Today was the big day of my first planned grafting attempt.
Trees cleaned up, branch prepared:






When I had everything set up, I started thinking about an idea that I got some time earlier.
With this grafting I would have one branch where I want, and would need some 2 more - I didn´t have them ready yet.
It would be very tedious work as the tree is quite small after all.
It would take some time to finish the plan - and as I saw how fast is this species growing and budding on top of the cuts....tadaaaaaa:




There were quite enough branches on top, so hopefully so many buds appear at the new cut and it will be easy job then to put them where I want.
I should have done that last year already and by now it would be somewhere else.
Thus I lost 1 year and have to start from the scratch on the main tree.
But hey - it might be worth it

So you didn't do the grafting after all?! Great to follow your progressions!

The top of the main tree I did cut rooted in a cup of water and became my first pre-bonsai of "mame" size.

The mame looks nice! Do you think you can reduce the leaves somehow in the future?