Ask 10 people and you'll get 10 different answers. I'm not going to give advice on this other than that a well-draining soil is essential. I notice you already started reading here:
www.bonsai4me.com/Basics/Basics_Soils.html
Also check the species specific guidelines on the same page.
There's more to find (and I'm sure you know how to Google for 'bonsai soil'), like:
www.colinlewisbonsai.com/Reading.html
www.kaizenbonsai.com/bonsai-tree-care-in...oil-for-bonsai-trees (long read...)
After reading both pages you'll know what I mean. About Akadama:
Graham Potter:
"There are two major drawbacks with this material [...] The [...] most significant, failing is that the product is not frost proof, in a climate like that of the U.K. Akadama can be reduced to dust after just a couple of severe winters and this will render it useless for cultivating bonsai"
Colin Lewis:
"Some growers complain that Akadama readily breaks down into much smaller particles and therefor impedes drainage, but they are not watching closely enough. Certainly it does break down, but this only means that the pore spaces become smaller, not that they disappear altogether. Since Akadama is not a clay, but a kind of cohesive sandy structure, it still drains efficiently after several years in use just as sand would."
Walter Pall:
"I do NOT at all endorse the usage of akadama for collected conifers and I do NOT endorse the usage of akadama in general in cold climate where trees will freeze. Akadama will decompose when the pot is frozen and it will deteriorate into clay which is very bad in a bonsai pot"
