i have a ficus gingseng, 2 taxus and a picea abies.
i want to use the decidous and needletreegroundmixes as described on this site.

decidous.
50% Akadama
25% Organic potting compost
25% Grit

Coniferous / Pine tree bonsai soil
60% Akadama
10% Organic potting compost
30% Grit

but does one of my trees which prefer a different mix?

You will have to experiment a lttle with soil. It is very dependent on your local climate, your care system and where the trees are. In general: Pine & Taxus tolerate / prefer dry soil (Less organic matter in the mixture) and your ficus will love moister soil, hence more organic matter.

leatherback wrote: You will have to experiment a lttle with soil. It is very dependent on your local climate, your care system and where the trees are. In general: Pine & Taxus tolerate / prefer dry soil (Less organic matter in the mixture) and your ficus will love moister soil, hence more organic matter.

i wanted to use the types described for the according tree.
so i wanted to know, are they qualified for it?

This is a bit odd. you are on a website. You read the composition of soil as advised per tree type. And then you ask on the same website whether the recipe they have on the site is correct...

leatherback wrote: This is a bit odd. you are on a website. You read the composition of soil as advised per tree type. And then you ask on the same website whether the recipe they have on the site is correct...

i did not realise that, but i wanted to ask if one of the trees is an exception, thats why.

akadama traditionaly comes in diferent hardness (soft medium hard ect...)
tropicals (your ficus) would benefit from a medium because it retains more water while conifers grow better in harder akadama.

some people grow their trees in strait akadama ,but fertalizing is a must.
soil is a big mystery, everyone ive spoke to about this suject has thier own formula and swear theirs is the best so i really dont think you should be too concerned. you have the basuics of what you will need